* [PATCH] drm/msm/dp: add atomic_check to bridge ops
@ 2022-08-17 18:01 Kuogee Hsieh
2022-08-22 16:18 ` Dmitry Baryshkov
0 siblings, 1 reply; 14+ messages in thread
From: Kuogee Hsieh @ 2022-08-17 18:01 UTC (permalink / raw)
To: robdclark, sean, swboyd, dianders, vkoul, daniel, airlied,
agross, dmitry.baryshkov, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_khsieh, quic_aravindh, freedreno
DRM commit_tails() will disable downstream crtc/encoder/bridge if
both disable crtc is required and crtc->active is set before pushing
a new frame downstream.
There is a rare case that user space display manager issue an extra
screen update immediately followed by close DRM device while down
stream display interface is disabled. This extra screen update will
timeout due to the downstream interface is disabled but will cause
crtc->active be set. Hence the followed commit_tails() called by
drm_release() will pass the disable downstream crtc/encoder/bridge
conditions checking even downstream interface is disabled.
This cause the crash to happen at dp_bridge_disable() due to it trying
to access the main link register to push the idle pattern out while main
link clocks is disabled.
This patch adds atomic_check to prevent the extra frame will not
be pushed down if display interface is down so that crtc->active
will not be set neither. This will fail the conditions checking
of disabling down stream crtc/encoder/bridge which prevent
drm_release() from calling dp_bridge_disable() so that crash
at dp_bridge_disable() prevented.
SError Interrupt on CPU7, code 0x00000000be000411 -- SError
CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
Hardware name: Google Lazor (rev3 - 8) (DT)
pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __cmpxchg_case_acq_32+0x14/0x2c
lr : do_raw_spin_lock+0xa4/0xdc
sp : ffffffc01092b6a0
x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
Kernel panic - not syncing: Asynchronous SError Interrupt
CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
Hardware name: Google Lazor (rev3 - 8) (DT)
Call trace:
dump_backtrace.part.0+0xbc/0xe4
show_stack+0x24/0x70
dump_stack_lvl+0x68/0x84
dump_stack+0x18/0x34
panic+0x14c/0x32c
nmi_panic+0x58/0x7c
arm64_serror_panic+0x78/0x84
do_serror+0x40/0x64
el1h_64_error_handler+0x30/0x48
el1h_64_error+0x68/0x6c
__cmpxchg_case_acq_32+0x14/0x2c
_raw_spin_lock_irqsave+0x38/0x4c
lock_timer_base+0x40/0x78
__mod_timer+0xf4/0x25c
schedule_timeout+0xd4/0xfc
__wait_for_common+0xac/0x140
wait_for_completion_timeout+0x2c/0x54
dp_ctrl_push_idle+0x40/0x88
dp_bridge_disable+0x24/0x30
drm_atomic_bridge_chain_disable+0x90/0xbc
drm_atomic_helper_commit_modeset_disables+0x198/0x444
msm_atomic_commit_tail+0x1d0/0x374
commit_tail+0x80/0x108
drm_atomic_helper_commit+0x118/0x11c
drm_atomic_commit+0xb4/0xe0
drm_client_modeset_commit_atomic+0x184/0x224
drm_client_modeset_commit_locked+0x58/0x160
drm_client_modeset_commit+0x3c/0x64
__drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
drm_fb_helper_set_par+0x74/0x80
drm_fb_helper_hotplug_event+0xdc/0xe0
__drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
drm_fb_helper_lastclose+0x20/0x2c
drm_lastclose+0x44/0x6c
drm_release+0x88/0xd4
__fput+0x104/0x220
____fput+0x1c/0x28
task_work_run+0x8c/0x100
do_exit+0x450/0x8d0
do_group_exit+0x40/0xac
__wake_up_parent+0x0/0x38
invoke_syscall+0x84/0x11c
el0_svc_common.constprop.0+0xb8/0xe4
do_el0_svc+0x8c/0xb8
el0_svc+0x2c/0x54
el0t_64_sync_handler+0x120/0x1c0
el0t_64_sync+0x190/0x194
SMP: stopping secondary CPUs
Kernel Offset: 0x128e800000 from 0xffffffc008000000
PHYS_OFFSET: 0x80000000
CPU features: 0x800,00c2a015,19801c82
Memory Limit: none
Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display enable and disable")
Reported-by: Leonard Lausen <leonard@lausen.nl>
Suggested-by: Rob Clark <robdclark@gmail.com>
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
---
drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
index 6df25f7..c682588 100644
--- a/drivers/gpu/drm/msm/dp/dp_drm.c
+++ b/drivers/gpu/drm/msm/dp/dp_drm.c
@@ -31,6 +31,25 @@ static enum drm_connector_status dp_bridge_detect(struct drm_bridge *bridge)
connector_status_disconnected;
}
+static int dp_bridge_atomic_check(struct drm_bridge *bridge,
+ struct drm_bridge_state *bridge_state,
+ struct drm_crtc_state *crtc_state,
+ struct drm_connector_state *conn_state)
+{
+ struct msm_dp *dp;
+
+ dp = to_dp_bridge(bridge)->dp_display;
+
+ drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
+ (dp->is_connected) ? "true" : "false");
+
+ if (bridge->ops & DRM_BRIDGE_OP_HPD)
+ return (dp->is_connected) ? 0 : -ENOTCONN;
+
+ return 0;
+}
+
+
/**
* dp_bridge_get_modes - callback to add drm modes via drm_mode_probed_add()
* @bridge: Poiner to drm bridge
@@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct drm_bridge *bridge, struct drm_connector *
}
static const struct drm_bridge_funcs dp_bridge_ops = {
+ .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
+ .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
+ .atomic_reset = drm_atomic_helper_bridge_reset,
.enable = dp_bridge_enable,
.disable = dp_bridge_disable,
.post_disable = dp_bridge_post_disable,
@@ -68,6 +90,7 @@ static const struct drm_bridge_funcs dp_bridge_ops = {
.mode_valid = dp_bridge_mode_valid,
.get_modes = dp_bridge_get_modes,
.detect = dp_bridge_detect,
+ .atomic_check = dp_bridge_atomic_check,
};
struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct drm_device *dev,
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-17 18:01 [PATCH] drm/msm/dp: add atomic_check to bridge ops Kuogee Hsieh
@ 2022-08-22 16:18 ` Dmitry Baryshkov
2022-08-22 16:38 ` Abhinav Kumar
0 siblings, 1 reply; 14+ messages in thread
From: Dmitry Baryshkov @ 2022-08-22 16:18 UTC (permalink / raw)
To: Kuogee Hsieh, robdclark, sean, swboyd, dianders, vkoul, daniel,
airlied, agross, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_aravindh, freedreno
On 17/08/2022 21:01, Kuogee Hsieh wrote:
> DRM commit_tails() will disable downstream crtc/encoder/bridge if
> both disable crtc is required and crtc->active is set before pushing
> a new frame downstream.
>
> There is a rare case that user space display manager issue an extra
> screen update immediately followed by close DRM device while down
> stream display interface is disabled. This extra screen update will
> timeout due to the downstream interface is disabled but will cause
> crtc->active be set. Hence the followed commit_tails() called by
> drm_release() will pass the disable downstream crtc/encoder/bridge
> conditions checking even downstream interface is disabled.
> This cause the crash to happen at dp_bridge_disable() due to it trying
> to access the main link register to push the idle pattern out while main
> link clocks is disabled.
>
> This patch adds atomic_check to prevent the extra frame will not
> be pushed down if display interface is down so that crtc->active
> will not be set neither. This will fail the conditions checking
> of disabling down stream crtc/encoder/bridge which prevent
> drm_release() from calling dp_bridge_disable() so that crash
> at dp_bridge_disable() prevented.
I must admit I had troubles parsing this description. However if I got
you right, I think the check that the main link clock is running in the
dp_bridge_disable() or dp_ctrl_push_idle() would be a better fix.
>
> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
> Hardware name: Google Lazor (rev3 - 8) (DT)
> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : __cmpxchg_case_acq_32+0x14/0x2c
> lr : do_raw_spin_lock+0xa4/0xdc
> sp : ffffffc01092b6a0
> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
> Kernel panic - not syncing: Asynchronous SError Interrupt
> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
> Hardware name: Google Lazor (rev3 - 8) (DT)
> Call trace:
> dump_backtrace.part.0+0xbc/0xe4
> show_stack+0x24/0x70
> dump_stack_lvl+0x68/0x84
> dump_stack+0x18/0x34
> panic+0x14c/0x32c
> nmi_panic+0x58/0x7c
> arm64_serror_panic+0x78/0x84
> do_serror+0x40/0x64
> el1h_64_error_handler+0x30/0x48
> el1h_64_error+0x68/0x6c
> __cmpxchg_case_acq_32+0x14/0x2c
> _raw_spin_lock_irqsave+0x38/0x4c
> lock_timer_base+0x40/0x78
> __mod_timer+0xf4/0x25c
> schedule_timeout+0xd4/0xfc
> __wait_for_common+0xac/0x140
> wait_for_completion_timeout+0x2c/0x54
> dp_ctrl_push_idle+0x40/0x88
> dp_bridge_disable+0x24/0x30
> drm_atomic_bridge_chain_disable+0x90/0xbc
> drm_atomic_helper_commit_modeset_disables+0x198/0x444
> msm_atomic_commit_tail+0x1d0/0x374
> commit_tail+0x80/0x108
> drm_atomic_helper_commit+0x118/0x11c
> drm_atomic_commit+0xb4/0xe0
> drm_client_modeset_commit_atomic+0x184/0x224
> drm_client_modeset_commit_locked+0x58/0x160
> drm_client_modeset_commit+0x3c/0x64
> __drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
> drm_fb_helper_set_par+0x74/0x80
> drm_fb_helper_hotplug_event+0xdc/0xe0
> __drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
> drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
> drm_fb_helper_lastclose+0x20/0x2c
> drm_lastclose+0x44/0x6c
> drm_release+0x88/0xd4
> __fput+0x104/0x220
> ____fput+0x1c/0x28
> task_work_run+0x8c/0x100
> do_exit+0x450/0x8d0
> do_group_exit+0x40/0xac
> __wake_up_parent+0x0/0x38
> invoke_syscall+0x84/0x11c
> el0_svc_common.constprop.0+0xb8/0xe4
> do_el0_svc+0x8c/0xb8
> el0_svc+0x2c/0x54
> el0t_64_sync_handler+0x120/0x1c0
> el0t_64_sync+0x190/0x194
> SMP: stopping secondary CPUs
> Kernel Offset: 0x128e800000 from 0xffffffc008000000
> PHYS_OFFSET: 0x80000000
> CPU features: 0x800,00c2a015,19801c82
> Memory Limit: none
>
> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display enable and disable")
> Reported-by: Leonard Lausen <leonard@lausen.nl>
> Suggested-by: Rob Clark <robdclark@gmail.com>
> Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
> drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
> index 6df25f7..c682588 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -31,6 +31,25 @@ static enum drm_connector_status dp_bridge_detect(struct drm_bridge *bridge)
> connector_status_disconnected;
> }
>
> +static int dp_bridge_atomic_check(struct drm_bridge *bridge,
> + struct drm_bridge_state *bridge_state,
> + struct drm_crtc_state *crtc_state,
> + struct drm_connector_state *conn_state)
> +{
> + struct msm_dp *dp;
> +
> + dp = to_dp_bridge(bridge)->dp_display;
> +
> + drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
> + (dp->is_connected) ? "true" : "false");
> +
> + if (bridge->ops & DRM_BRIDGE_OP_HPD)
> + return (dp->is_connected) ? 0 : -ENOTCONN;
> +
> + return 0;
> +}
> +
> +
> /**
> * dp_bridge_get_modes - callback to add drm modes via drm_mode_probed_add()
> * @bridge: Poiner to drm bridge
> @@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct drm_bridge *bridge, struct drm_connector *
> }
>
> static const struct drm_bridge_funcs dp_bridge_ops = {
> + .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> + .atomic_reset = drm_atomic_helper_bridge_reset,
> .enable = dp_bridge_enable,
> .disable = dp_bridge_disable,
> .post_disable = dp_bridge_post_disable,
> @@ -68,6 +90,7 @@ static const struct drm_bridge_funcs dp_bridge_ops = {
> .mode_valid = dp_bridge_mode_valid,
> .get_modes = dp_bridge_get_modes,
> .detect = dp_bridge_detect,
> + .atomic_check = dp_bridge_atomic_check,
> };
>
> struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct drm_device *dev,
--
With best wishes
Dmitry
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-22 16:18 ` Dmitry Baryshkov
@ 2022-08-22 16:38 ` Abhinav Kumar
2022-08-22 16:49 ` Dmitry Baryshkov
0 siblings, 1 reply; 14+ messages in thread
From: Abhinav Kumar @ 2022-08-22 16:38 UTC (permalink / raw)
To: Dmitry Baryshkov, Kuogee Hsieh, robdclark, sean, swboyd,
dianders, vkoul, daniel, airlied, agross, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_aravindh, freedreno
Hi Dmitry
On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>> both disable crtc is required and crtc->active is set before pushing
>> a new frame downstream.
>>
>> There is a rare case that user space display manager issue an extra
>> screen update immediately followed by close DRM device while down
>> stream display interface is disabled. This extra screen update will
>> timeout due to the downstream interface is disabled but will cause
>> crtc->active be set. Hence the followed commit_tails() called by
>> drm_release() will pass the disable downstream crtc/encoder/bridge
>> conditions checking even downstream interface is disabled.
>> This cause the crash to happen at dp_bridge_disable() due to it trying
>> to access the main link register to push the idle pattern out while main
>> link clocks is disabled.
>>
>> This patch adds atomic_check to prevent the extra frame will not
>> be pushed down if display interface is down so that crtc->active
>> will not be set neither. This will fail the conditions checking
>> of disabling down stream crtc/encoder/bridge which prevent
>> drm_release() from calling dp_bridge_disable() so that crash
>> at dp_bridge_disable() prevented.
>
> I must admit I had troubles parsing this description. However if I got
> you right, I think the check that the main link clock is running in the
> dp_bridge_disable() or dp_ctrl_push_idle() would be a better fix.
Originally, thats what was posted
https://patchwork.freedesktop.org/patch/496984/.
Then it seemed like we were just protecting against an issue in the
framework which was allowing the frames to be pushed even after the
display was disconnected. The DP driver did send out the disconnect
event correctly and as per the logs, this frame came down after that and
the DRM fwk did allow it.
So after discussing on IRC with Rob, we came up with this approach that
if the display is not connected, then atomic_check should fail. That way
the commit will not happen.
Just seemed a bit cleaner instead of adding all our protections.
>
>>
>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>> Hardware name: Google Lazor (rev3 - 8) (DT)
>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>> lr : do_raw_spin_lock+0xa4/0xdc
>> sp : ffffffc01092b6a0
>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>> Kernel panic - not syncing: Asynchronous SError Interrupt
>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>> Hardware name: Google Lazor (rev3 - 8) (DT)
>> Call trace:
>> dump_backtrace.part.0+0xbc/0xe4
>> show_stack+0x24/0x70
>> dump_stack_lvl+0x68/0x84
>> dump_stack+0x18/0x34
>> panic+0x14c/0x32c
>> nmi_panic+0x58/0x7c
>> arm64_serror_panic+0x78/0x84
>> do_serror+0x40/0x64
>> el1h_64_error_handler+0x30/0x48
>> el1h_64_error+0x68/0x6c
>> __cmpxchg_case_acq_32+0x14/0x2c
>> _raw_spin_lock_irqsave+0x38/0x4c
>> lock_timer_base+0x40/0x78
>> __mod_timer+0xf4/0x25c
>> schedule_timeout+0xd4/0xfc
>> __wait_for_common+0xac/0x140
>> wait_for_completion_timeout+0x2c/0x54
>> dp_ctrl_push_idle+0x40/0x88
>> dp_bridge_disable+0x24/0x30
>> drm_atomic_bridge_chain_disable+0x90/0xbc
>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>> msm_atomic_commit_tail+0x1d0/0x374
>> commit_tail+0x80/0x108
>> drm_atomic_helper_commit+0x118/0x11c
>> drm_atomic_commit+0xb4/0xe0
>> drm_client_modeset_commit_atomic+0x184/0x224
>> drm_client_modeset_commit_locked+0x58/0x160
>> drm_client_modeset_commit+0x3c/0x64
>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
>> drm_fb_helper_set_par+0x74/0x80
>> drm_fb_helper_hotplug_event+0xdc/0xe0
>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
>> drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
>> drm_fb_helper_lastclose+0x20/0x2c
>> drm_lastclose+0x44/0x6c
>> drm_release+0x88/0xd4
>> __fput+0x104/0x220
>> ____fput+0x1c/0x28
>> task_work_run+0x8c/0x100
>> do_exit+0x450/0x8d0
>> do_group_exit+0x40/0xac
>> __wake_up_parent+0x0/0x38
>> invoke_syscall+0x84/0x11c
>> el0_svc_common.constprop.0+0xb8/0xe4
>> do_el0_svc+0x8c/0xb8
>> el0_svc+0x2c/0x54
>> el0t_64_sync_handler+0x120/0x1c0
>> el0t_64_sync+0x190/0x194
>> SMP: stopping secondary CPUs
>> Kernel Offset: 0x128e800000 from 0xffffffc008000000
>> PHYS_OFFSET: 0x80000000
>> CPU features: 0x800,00c2a015,19801c82
>> Memory Limit: none
>>
>> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display
>> enable and disable")
>> Reported-by: Leonard Lausen <leonard@lausen.nl>
>> Suggested-by: Rob Clark <robdclark@gmail.com>
>> Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>> ---
>> drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
>> 1 file changed, 23 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c
>> b/drivers/gpu/drm/msm/dp/dp_drm.c
>> index 6df25f7..c682588 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>> @@ -31,6 +31,25 @@ static enum drm_connector_status
>> dp_bridge_detect(struct drm_bridge *bridge)
>> connector_status_disconnected;
>> }
>> +static int dp_bridge_atomic_check(struct drm_bridge *bridge,
>> + struct drm_bridge_state *bridge_state,
>> + struct drm_crtc_state *crtc_state,
>> + struct drm_connector_state *conn_state)
>> +{
>> + struct msm_dp *dp;
>> +
>> + dp = to_dp_bridge(bridge)->dp_display;
>> +
>> + drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
>> + (dp->is_connected) ? "true" : "false");
>> +
>> + if (bridge->ops & DRM_BRIDGE_OP_HPD)
>> + return (dp->is_connected) ? 0 : -ENOTCONN;
>> +
>> + return 0;
>> +}
>> +
>> +
>> /**
>> * dp_bridge_get_modes - callback to add drm modes via
>> drm_mode_probed_add()
>> * @bridge: Poiner to drm bridge
>> @@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct drm_bridge
>> *bridge, struct drm_connector *
>> }
>> static const struct drm_bridge_funcs dp_bridge_ops = {
>> + .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
>> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
>> + .atomic_reset = drm_atomic_helper_bridge_reset,
>> .enable = dp_bridge_enable,
>> .disable = dp_bridge_disable,
>> .post_disable = dp_bridge_post_disable,
>> @@ -68,6 +90,7 @@ static const struct drm_bridge_funcs dp_bridge_ops = {
>> .mode_valid = dp_bridge_mode_valid,
>> .get_modes = dp_bridge_get_modes,
>> .detect = dp_bridge_detect,
>> + .atomic_check = dp_bridge_atomic_check,
>> };
>> struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct
>> drm_device *dev,
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-22 16:38 ` Abhinav Kumar
@ 2022-08-22 16:49 ` Dmitry Baryshkov
2022-08-22 17:32 ` Abhinav Kumar
0 siblings, 1 reply; 14+ messages in thread
From: Dmitry Baryshkov @ 2022-08-22 16:49 UTC (permalink / raw)
To: Abhinav Kumar, Kuogee Hsieh, robdclark, sean, swboyd, dianders,
vkoul, daniel, airlied, agross, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_aravindh, freedreno
On 22/08/2022 19:38, Abhinav Kumar wrote:
> Hi Dmitry
>
> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>>> both disable crtc is required and crtc->active is set before pushing
>>> a new frame downstream.
>>>
>>> There is a rare case that user space display manager issue an extra
>>> screen update immediately followed by close DRM device while down
>>> stream display interface is disabled. This extra screen update will
>>> timeout due to the downstream interface is disabled but will cause
>>> crtc->active be set. Hence the followed commit_tails() called by
>>> drm_release() will pass the disable downstream crtc/encoder/bridge
>>> conditions checking even downstream interface is disabled.
>>> This cause the crash to happen at dp_bridge_disable() due to it trying
>>> to access the main link register to push the idle pattern out while main
>>> link clocks is disabled.
>>>
>>> This patch adds atomic_check to prevent the extra frame will not
>>> be pushed down if display interface is down so that crtc->active
>>> will not be set neither. This will fail the conditions checking
>>> of disabling down stream crtc/encoder/bridge which prevent
>>> drm_release() from calling dp_bridge_disable() so that crash
>>> at dp_bridge_disable() prevented.
>>
>> I must admit I had troubles parsing this description. However if I got
>> you right, I think the check that the main link clock is running in
>> the dp_bridge_disable() or dp_ctrl_push_idle() would be a better fix.
>
> Originally, thats what was posted
> https://patchwork.freedesktop.org/patch/496984/.
This patch is also not so correct from my POV. It checks for the hpd
status, while in reality it should check for main link clocks being enabled.
>
> Then it seemed like we were just protecting against an issue in the
> framework which was allowing the frames to be pushed even after the
> display was disconnected. The DP driver did send out the disconnect
> event correctly and as per the logs, this frame came down after that and
> the DRM fwk did allow it.
>
> So after discussing on IRC with Rob, we came up with this approach that
> if the display is not connected, then atomic_check should fail. That way
> the commit will not happen.
>
> Just seemed a bit cleaner instead of adding all our protections.
The check to fail atomic_check if display is not connected seems out of
place. In its current way it begs go to the upper layer, forbidding
using disconnected sinks for all the drivers. There is nothing special
in the MSM DP driver with respect to the HPD events processing and
failing atomic_check() based on that.
>
>>
>>>
>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>> lr : do_raw_spin_lock+0xa4/0xdc
>>> sp : ffffffc01092b6a0
>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>> Call trace:
>>> dump_backtrace.part.0+0xbc/0xe4
>>> show_stack+0x24/0x70
>>> dump_stack_lvl+0x68/0x84
>>> dump_stack+0x18/0x34
>>> panic+0x14c/0x32c
>>> nmi_panic+0x58/0x7c
>>> arm64_serror_panic+0x78/0x84
>>> do_serror+0x40/0x64
>>> el1h_64_error_handler+0x30/0x48
>>> el1h_64_error+0x68/0x6c
>>> __cmpxchg_case_acq_32+0x14/0x2c
>>> _raw_spin_lock_irqsave+0x38/0x4c
>>> lock_timer_base+0x40/0x78
>>> __mod_timer+0xf4/0x25c
>>> schedule_timeout+0xd4/0xfc
>>> __wait_for_common+0xac/0x140
>>> wait_for_completion_timeout+0x2c/0x54
>>> dp_ctrl_push_idle+0x40/0x88
>>> dp_bridge_disable+0x24/0x30
>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>> msm_atomic_commit_tail+0x1d0/0x374
>>> commit_tail+0x80/0x108
>>> drm_atomic_helper_commit+0x118/0x11c
>>> drm_atomic_commit+0xb4/0xe0
>>> drm_client_modeset_commit_atomic+0x184/0x224
>>> drm_client_modeset_commit_locked+0x58/0x160
>>> drm_client_modeset_commit+0x3c/0x64
>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
>>> drm_fb_helper_set_par+0x74/0x80
>>> drm_fb_helper_hotplug_event+0xdc/0xe0
>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
>>> drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
>>> drm_fb_helper_lastclose+0x20/0x2c
>>> drm_lastclose+0x44/0x6c
>>> drm_release+0x88/0xd4
>>> __fput+0x104/0x220
>>> ____fput+0x1c/0x28
>>> task_work_run+0x8c/0x100
>>> do_exit+0x450/0x8d0
>>> do_group_exit+0x40/0xac
>>> __wake_up_parent+0x0/0x38
>>> invoke_syscall+0x84/0x11c
>>> el0_svc_common.constprop.0+0xb8/0xe4
>>> do_el0_svc+0x8c/0xb8
>>> el0_svc+0x2c/0x54
>>> el0t_64_sync_handler+0x120/0x1c0
>>> el0t_64_sync+0x190/0x194
>>> SMP: stopping secondary CPUs
>>> Kernel Offset: 0x128e800000 from 0xffffffc008000000
>>> PHYS_OFFSET: 0x80000000
>>> CPU features: 0x800,00c2a015,19801c82
>>> Memory Limit: none
>>>
>>> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display
>>> enable and disable")
>>> Reported-by: Leonard Lausen <leonard@lausen.nl>
>>> Suggested-by: Rob Clark <robdclark@gmail.com>
>>> Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>>> ---
>>> drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
>>> 1 file changed, 23 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c
>>> b/drivers/gpu/drm/msm/dp/dp_drm.c
>>> index 6df25f7..c682588 100644
>>> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
>>> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>>> @@ -31,6 +31,25 @@ static enum drm_connector_status
>>> dp_bridge_detect(struct drm_bridge *bridge)
>>> connector_status_disconnected;
>>> }
>>> +static int dp_bridge_atomic_check(struct drm_bridge *bridge,
>>> + struct drm_bridge_state *bridge_state,
>>> + struct drm_crtc_state *crtc_state,
>>> + struct drm_connector_state *conn_state)
>>> +{
>>> + struct msm_dp *dp;
>>> +
>>> + dp = to_dp_bridge(bridge)->dp_display;
>>> +
>>> + drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
>>> + (dp->is_connected) ? "true" : "false");
>>> +
>>> + if (bridge->ops & DRM_BRIDGE_OP_HPD)
>>> + return (dp->is_connected) ? 0 : -ENOTCONN;
This raises questions if this will work for the configurations when
other bridge is used for HPD events.
Let's not mix the levels of processing. If we should not disable the
link because it is already disabled, let's just do so rather than
failing the atomic_check().
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +
>>> /**
>>> * dp_bridge_get_modes - callback to add drm modes via
>>> drm_mode_probed_add()
>>> * @bridge: Poiner to drm bridge
>>> @@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct drm_bridge
>>> *bridge, struct drm_connector *
>>> }
>>> static const struct drm_bridge_funcs dp_bridge_ops = {
>>> + .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
>>> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
>>> + .atomic_reset = drm_atomic_helper_bridge_reset,
>>> .enable = dp_bridge_enable,
>>> .disable = dp_bridge_disable,
>>> .post_disable = dp_bridge_post_disable,
>>> @@ -68,6 +90,7 @@ static const struct drm_bridge_funcs dp_bridge_ops = {
>>> .mode_valid = dp_bridge_mode_valid,
>>> .get_modes = dp_bridge_get_modes,
>>> .detect = dp_bridge_detect,
>>> + .atomic_check = dp_bridge_atomic_check,
>>> };
>>> struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct
>>> drm_device *dev,
>>
--
With best wishes
Dmitry
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-22 16:49 ` Dmitry Baryshkov
@ 2022-08-22 17:32 ` Abhinav Kumar
2022-08-22 18:33 ` Dmitry Baryshkov
0 siblings, 1 reply; 14+ messages in thread
From: Abhinav Kumar @ 2022-08-22 17:32 UTC (permalink / raw)
To: Dmitry Baryshkov, Kuogee Hsieh, robdclark, sean, swboyd,
dianders, vkoul, daniel, airlied, agross, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_aravindh, freedreno
On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
> On 22/08/2022 19:38, Abhinav Kumar wrote:
>> Hi Dmitry
>>
>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>>>> both disable crtc is required and crtc->active is set before pushing
>>>> a new frame downstream.
>>>>
>>>> There is a rare case that user space display manager issue an extra
>>>> screen update immediately followed by close DRM device while down
>>>> stream display interface is disabled. This extra screen update will
>>>> timeout due to the downstream interface is disabled but will cause
>>>> crtc->active be set. Hence the followed commit_tails() called by
>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
>>>> conditions checking even downstream interface is disabled.
>>>> This cause the crash to happen at dp_bridge_disable() due to it trying
>>>> to access the main link register to push the idle pattern out while
>>>> main
>>>> link clocks is disabled.
>>>>
>>>> This patch adds atomic_check to prevent the extra frame will not
>>>> be pushed down if display interface is down so that crtc->active
>>>> will not be set neither. This will fail the conditions checking
>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>> at dp_bridge_disable() prevented.
>>>
>>> I must admit I had troubles parsing this description. However if I
>>> got you right, I think the check that the main link clock is running
>>> in the dp_bridge_disable() or dp_ctrl_push_idle() would be a better fix.
>>
>> Originally, thats what was posted
>> https://patchwork.freedesktop.org/patch/496984/.
>
> This patch is also not so correct from my POV. It checks for the hpd
> status, while in reality it should check for main link clocks being
> enabled.
>
We can push another fix to check for the clk state instead of the hpd
status. But I must say we are again just masking something which the fwk
should have avoided isnt it?
As per the doc in the include/drm/drm_bridge.h it says,
"*
* The bridge can assume that the display pipe (i.e. clocks and timing
* signals) feeding it is still running when this callback is called.
*"
By adding an extra layers of protection in the driver, we are just
avoiding another issue but the commit should not have been issued in the
first place.
So shouldnt we do both then? That is add protection to check if clock is
ON and also, reject commits when display is disconnected.
>>
>> Then it seemed like we were just protecting against an issue in the
>> framework which was allowing the frames to be pushed even after the
>> display was disconnected. The DP driver did send out the disconnect
>> event correctly and as per the logs, this frame came down after that
>> and the DRM fwk did allow it.
>>
>> So after discussing on IRC with Rob, we came up with this approach that
>> if the display is not connected, then atomic_check should fail. That
>> way the commit will not happen.
>>
>> Just seemed a bit cleaner instead of adding all our protections.
>
> The check to fail atomic_check if display is not connected seems out of
> place. In its current way it begs go to the upper layer, forbidding
> using disconnected sinks for all the drivers. There is nothing special
> in the MSM DP driver with respect to the HPD events processing and
> failing atomic_check() based on that.
>
Why all the drivers? This is only for MSM DP bridge.
>>
>>>
>>>>
>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>> sp : ffffffc01092b6a0
>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>> Call trace:
>>>> dump_backtrace.part.0+0xbc/0xe4
>>>> show_stack+0x24/0x70
>>>> dump_stack_lvl+0x68/0x84
>>>> dump_stack+0x18/0x34
>>>> panic+0x14c/0x32c
>>>> nmi_panic+0x58/0x7c
>>>> arm64_serror_panic+0x78/0x84
>>>> do_serror+0x40/0x64
>>>> el1h_64_error_handler+0x30/0x48
>>>> el1h_64_error+0x68/0x6c
>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>> _raw_spin_lock_irqsave+0x38/0x4c
>>>> lock_timer_base+0x40/0x78
>>>> __mod_timer+0xf4/0x25c
>>>> schedule_timeout+0xd4/0xfc
>>>> __wait_for_common+0xac/0x140
>>>> wait_for_completion_timeout+0x2c/0x54
>>>> dp_ctrl_push_idle+0x40/0x88
>>>> dp_bridge_disable+0x24/0x30
>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>> commit_tail+0x80/0x108
>>>> drm_atomic_helper_commit+0x118/0x11c
>>>> drm_atomic_commit+0xb4/0xe0
>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>> drm_client_modeset_commit+0x3c/0x64
>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
>>>> drm_fb_helper_set_par+0x74/0x80
>>>> drm_fb_helper_hotplug_event+0xdc/0xe0
>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
>>>> drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
>>>> drm_fb_helper_lastclose+0x20/0x2c
>>>> drm_lastclose+0x44/0x6c
>>>> drm_release+0x88/0xd4
>>>> __fput+0x104/0x220
>>>> ____fput+0x1c/0x28
>>>> task_work_run+0x8c/0x100
>>>> do_exit+0x450/0x8d0
>>>> do_group_exit+0x40/0xac
>>>> __wake_up_parent+0x0/0x38
>>>> invoke_syscall+0x84/0x11c
>>>> el0_svc_common.constprop.0+0xb8/0xe4
>>>> do_el0_svc+0x8c/0xb8
>>>> el0_svc+0x2c/0x54
>>>> el0t_64_sync_handler+0x120/0x1c0
>>>> el0t_64_sync+0x190/0x194
>>>> SMP: stopping secondary CPUs
>>>> Kernel Offset: 0x128e800000 from 0xffffffc008000000
>>>> PHYS_OFFSET: 0x80000000
>>>> CPU features: 0x800,00c2a015,19801c82
>>>> Memory Limit: none
>>>>
>>>> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for
>>>> display enable and disable")
>>>> Reported-by: Leonard Lausen <leonard@lausen.nl>
>>>> Suggested-by: Rob Clark <robdclark@gmail.com>
>>>> Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
>>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>>>> ---
>>>> drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
>>>> 1 file changed, 23 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>> b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>> index 6df25f7..c682588 100644
>>>> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>> @@ -31,6 +31,25 @@ static enum drm_connector_status
>>>> dp_bridge_detect(struct drm_bridge *bridge)
>>>> connector_status_disconnected;
>>>> }
>>>> +static int dp_bridge_atomic_check(struct drm_bridge *bridge,
>>>> + struct drm_bridge_state *bridge_state,
>>>> + struct drm_crtc_state *crtc_state,
>>>> + struct drm_connector_state *conn_state)
>>>> +{
>>>> + struct msm_dp *dp;
>>>> +
>>>> + dp = to_dp_bridge(bridge)->dp_display;
>>>> +
>>>> + drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
>>>> + (dp->is_connected) ? "true" : "false");
>>>> +
>>>> + if (bridge->ops & DRM_BRIDGE_OP_HPD)
>>>> + return (dp->is_connected) ? 0 : -ENOTCONN;
>
> This raises questions if this will work for the configurations when
> other bridge is used for HPD events.
>
> Let's not mix the levels of processing. If we should not disable the
> link because it is already disabled, let's just do so rather than
> failing the atomic_check().
>
This is only for MSM DP's bridge. If we use another bridge which is
capable of handling its own HPD, then that time MSM DP's bridge shouldnt
set this flag.
We can even replace this check with just checking if connector_type is
DP but that would again open the discussion of having DP/eDP specific
checks so we did it this way.
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> +
>>>> /**
>>>> * dp_bridge_get_modes - callback to add drm modes via
>>>> drm_mode_probed_add()
>>>> * @bridge: Poiner to drm bridge
>>>> @@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct drm_bridge
>>>> *bridge, struct drm_connector *
>>>> }
>>>> static const struct drm_bridge_funcs dp_bridge_ops = {
>>>> + .atomic_duplicate_state =
>>>> drm_atomic_helper_bridge_duplicate_state,
>>>> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
>>>> + .atomic_reset = drm_atomic_helper_bridge_reset,
>>>> .enable = dp_bridge_enable,
>>>> .disable = dp_bridge_disable,
>>>> .post_disable = dp_bridge_post_disable,
>>>> @@ -68,6 +90,7 @@ static const struct drm_bridge_funcs dp_bridge_ops
>>>> = {
>>>> .mode_valid = dp_bridge_mode_valid,
>>>> .get_modes = dp_bridge_get_modes,
>>>> .detect = dp_bridge_detect,
>>>> + .atomic_check = dp_bridge_atomic_check,
>>>> };
>>>> struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display,
>>>> struct drm_device *dev,
>>>
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-22 17:32 ` Abhinav Kumar
@ 2022-08-22 18:33 ` Dmitry Baryshkov
2022-08-23 22:07 ` Abhinav Kumar
0 siblings, 1 reply; 14+ messages in thread
From: Dmitry Baryshkov @ 2022-08-22 18:33 UTC (permalink / raw)
To: Abhinav Kumar, Kuogee Hsieh, robdclark, sean, swboyd, dianders,
vkoul, daniel, airlied, agross, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_aravindh, freedreno
On 22/08/2022 20:32, Abhinav Kumar wrote:
>
>
> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
>> On 22/08/2022 19:38, Abhinav Kumar wrote:
>>> Hi Dmitry
>>>
>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>>>>> both disable crtc is required and crtc->active is set before pushing
>>>>> a new frame downstream.
>>>>>
>>>>> There is a rare case that user space display manager issue an extra
>>>>> screen update immediately followed by close DRM device while down
>>>>> stream display interface is disabled. This extra screen update will
>>>>> timeout due to the downstream interface is disabled but will cause
>>>>> crtc->active be set. Hence the followed commit_tails() called by
>>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
>>>>> conditions checking even downstream interface is disabled.
>>>>> This cause the crash to happen at dp_bridge_disable() due to it trying
>>>>> to access the main link register to push the idle pattern out while
>>>>> main
>>>>> link clocks is disabled.
>>>>>
>>>>> This patch adds atomic_check to prevent the extra frame will not
>>>>> be pushed down if display interface is down so that crtc->active
>>>>> will not be set neither. This will fail the conditions checking
>>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>>> at dp_bridge_disable() prevented.
>>>>
>>>> I must admit I had troubles parsing this description. However if I
>>>> got you right, I think the check that the main link clock is running
>>>> in the dp_bridge_disable() or dp_ctrl_push_idle() would be a better
>>>> fix.
>>>
>>> Originally, thats what was posted
>>> https://patchwork.freedesktop.org/patch/496984/.
>>
>> This patch is also not so correct from my POV. It checks for the hpd
>> status, while in reality it should check for main link clocks being
>> enabled.
>>
>
> We can push another fix to check for the clk state instead of the hpd
> status. But I must say we are again just masking something which the fwk
> should have avoided isnt it?
>
> As per the doc in the include/drm/drm_bridge.h it says,
>
> "*
> * The bridge can assume that the display pipe (i.e. clocks and timing
> * signals) feeding it is still running when this callback is called.
> *"
Yes, that's what I meant about this chunk begging to go to the core. In
my opinion, if we are talking about the disconnected sinks, it is the
framework who should disallow submitting the frames to the disconnected
sinks.
>
> By adding an extra layers of protection in the driver, we are just
> avoiding another issue but the commit should not have been issued in the
> first place.
>
> So shouldnt we do both then? That is add protection to check if clock is
> ON and also, reject commits when display is disconnected.
>
>>>
>>> Then it seemed like we were just protecting against an issue in the
>>> framework which was allowing the frames to be pushed even after the
>>> display was disconnected. The DP driver did send out the disconnect
>>> event correctly and as per the logs, this frame came down after that
>>> and the DRM fwk did allow it.
>>>
>>> So after discussing on IRC with Rob, we came up with this approach that
>>> if the display is not connected, then atomic_check should fail. That
>>> way the commit will not happen.
>>>
>>> Just seemed a bit cleaner instead of adding all our protections.
>>
>> The check to fail atomic_check if display is not connected seems out
>> of place. In its current way it begs go to the upper layer, forbidding
>> using disconnected sinks for all the drivers. There is nothing special
>> in the MSM DP driver with respect to the HPD events processing and
>> failing atomic_check() based on that.
>>
>
> Why all the drivers? This is only for MSM DP bridge.
Yes, we change the MSM DRM driver. But the check is generic enough. I'm
not actually insisting on pushing the check to the core, just trying to
understand the real cause here.
>
>>>
>>>>
>>>>>
>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>>> sp : ffffffc01092b6a0
>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>> Call trace:
>>>>> dump_backtrace.part.0+0xbc/0xe4
>>>>> show_stack+0x24/0x70
>>>>> dump_stack_lvl+0x68/0x84
>>>>> dump_stack+0x18/0x34
>>>>> panic+0x14c/0x32c
>>>>> nmi_panic+0x58/0x7c
>>>>> arm64_serror_panic+0x78/0x84
>>>>> do_serror+0x40/0x64
>>>>> el1h_64_error_handler+0x30/0x48
>>>>> el1h_64_error+0x68/0x6c
>>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>>> _raw_spin_lock_irqsave+0x38/0x4c
You know, after re-reading the trace, I could not help but notice that
the issue seems to be related to completion/timer/spinlock memory
becoming unavailable rather than disabling the main link clock.
See, the SError comes in the spin_lock path, not during register read.
Thus I think the commit message is a bit misleading.
Can we please get a trace checking which calls were actually made for
the dp bridge and if the dp/dp->ctrl memory pointers are correct?
I do not see the dp_display_disable() being called. Maybe I just missed
the call.
>>>>> lock_timer_base+0x40/0x78
>>>>> __mod_timer+0xf4/0x25c
>>>>> schedule_timeout+0xd4/0xfc
>>>>> __wait_for_common+0xac/0x140
>>>>> wait_for_completion_timeout+0x2c/0x54
>>>>> dp_ctrl_push_idle+0x40/0x88
>>>>> dp_bridge_disable+0x24/0x30
>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>>> commit_tail+0x80/0x108
>>>>> drm_atomic_helper_commit+0x118/0x11c
>>>>> drm_atomic_commit+0xb4/0xe0
>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>>> drm_client_modeset_commit+0x3c/0x64
>>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
>>>>> drm_fb_helper_set_par+0x74/0x80
>>>>> drm_fb_helper_hotplug_event+0xdc/0xe0
>>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
>>>>> drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
>>>>> drm_fb_helper_lastclose+0x20/0x2c
>>>>> drm_lastclose+0x44/0x6c
>>>>> drm_release+0x88/0xd4
>>>>> __fput+0x104/0x220
>>>>> ____fput+0x1c/0x28
>>>>> task_work_run+0x8c/0x100
>>>>> do_exit+0x450/0x8d0
>>>>> do_group_exit+0x40/0xac
>>>>> __wake_up_parent+0x0/0x38
>>>>> invoke_syscall+0x84/0x11c
>>>>> el0_svc_common.constprop.0+0xb8/0xe4
>>>>> do_el0_svc+0x8c/0xb8
>>>>> el0_svc+0x2c/0x54
>>>>> el0t_64_sync_handler+0x120/0x1c0
>>>>> el0t_64_sync+0x190/0x194
>>>>> SMP: stopping secondary CPUs
>>>>> Kernel Offset: 0x128e800000 from 0xffffffc008000000
>>>>> PHYS_OFFSET: 0x80000000
>>>>> CPU features: 0x800,00c2a015,19801c82
>>>>> Memory Limit: none
>>>>>
>>>>> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for
>>>>> display enable and disable")
>>>>> Reported-by: Leonard Lausen <leonard@lausen.nl>
>>>>> Suggested-by: Rob Clark <robdclark@gmail.com>
>>>>> Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
>>>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>>>>> ---
>>>>> drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
>>>>> 1 file changed, 23 insertions(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>> b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>> index 6df25f7..c682588 100644
>>>>> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>> @@ -31,6 +31,25 @@ static enum drm_connector_status
>>>>> dp_bridge_detect(struct drm_bridge *bridge)
>>>>> connector_status_disconnected;
>>>>> }
>>>>> +static int dp_bridge_atomic_check(struct drm_bridge *bridge,
>>>>> + struct drm_bridge_state *bridge_state,
>>>>> + struct drm_crtc_state *crtc_state,
>>>>> + struct drm_connector_state *conn_state)
>>>>> +{
>>>>> + struct msm_dp *dp;
>>>>> +
>>>>> + dp = to_dp_bridge(bridge)->dp_display;
>>>>> +
>>>>> + drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
>>>>> + (dp->is_connected) ? "true" : "false");
>>>>> +
>>>>> + if (bridge->ops & DRM_BRIDGE_OP_HPD)
>>>>> + return (dp->is_connected) ? 0 : -ENOTCONN;
>>
>> This raises questions if this will work for the configurations when
>> other bridge is used for HPD events.
>>
>> Let's not mix the levels of processing. If we should not disable the
>> link because it is already disabled, let's just do so rather than
>> failing the atomic_check().
>>
>
> This is only for MSM DP's bridge. If we use another bridge which is
> capable of handling its own HPD, then that time MSM DP's bridge shouldnt
> set this flag.
Not quite. The bridges set the ops to describe the ops that they support
themselves. Then the drm_bridge_connectors selects the bridge handling
hpd, etc. So the DRM_BRIDGE_OP_HPD is always set for DP sources. But the
question is quite the opposite: if we have the next bridge (e.g. the
usb-c-connector or the display-connector), will the is_connected field
be set correctly?
>
> We can even replace this check with just checking if connector_type is
> DP but that would again open the discussion of having DP/eDP specific
> checks so we did it this way.
>
>
>>>>> +
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>> +
>>>>> /**
>>>>> * dp_bridge_get_modes - callback to add drm modes via
>>>>> drm_mode_probed_add()
>>>>> * @bridge: Poiner to drm bridge
>>>>> @@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct drm_bridge
>>>>> *bridge, struct drm_connector *
>>>>> }
>>>>> static const struct drm_bridge_funcs dp_bridge_ops = {
>>>>> + .atomic_duplicate_state =
>>>>> drm_atomic_helper_bridge_duplicate_state,
>>>>> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
>>>>> + .atomic_reset = drm_atomic_helper_bridge_reset,
>>>>> .enable = dp_bridge_enable,
>>>>> .disable = dp_bridge_disable,
>>>>> .post_disable = dp_bridge_post_disable,
>>>>> @@ -68,6 +90,7 @@ static const struct drm_bridge_funcs
>>>>> dp_bridge_ops = {
>>>>> .mode_valid = dp_bridge_mode_valid,
>>>>> .get_modes = dp_bridge_get_modes,
>>>>> .detect = dp_bridge_detect,
>>>>> + .atomic_check = dp_bridge_atomic_check,
>>>>> };
>>>>> struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display,
>>>>> struct drm_device *dev,
>>>>
>>
--
With best wishes
Dmitry
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-22 18:33 ` Dmitry Baryshkov
@ 2022-08-23 22:07 ` Abhinav Kumar
2022-08-23 22:18 ` Abhinav Kumar
2022-08-23 22:41 ` Dmitry Baryshkov
0 siblings, 2 replies; 14+ messages in thread
From: Abhinav Kumar @ 2022-08-23 22:07 UTC (permalink / raw)
To: Dmitry Baryshkov, Kuogee Hsieh, robdclark, sean, swboyd,
dianders, vkoul, daniel, airlied, agross, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_aravindh, freedreno
On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
> On 22/08/2022 20:32, Abhinav Kumar wrote:
>>
>>
>> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
>>> On 22/08/2022 19:38, Abhinav Kumar wrote:
>>>> Hi Dmitry
>>>>
>>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>>>>>> both disable crtc is required and crtc->active is set before pushing
>>>>>> a new frame downstream.
>>>>>>
>>>>>> There is a rare case that user space display manager issue an extra
>>>>>> screen update immediately followed by close DRM device while down
>>>>>> stream display interface is disabled. This extra screen update will
>>>>>> timeout due to the downstream interface is disabled but will cause
>>>>>> crtc->active be set. Hence the followed commit_tails() called by
>>>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
>>>>>> conditions checking even downstream interface is disabled.
>>>>>> This cause the crash to happen at dp_bridge_disable() due to it
>>>>>> trying
>>>>>> to access the main link register to push the idle pattern out
>>>>>> while main
>>>>>> link clocks is disabled.
>>>>>>
>>>>>> This patch adds atomic_check to prevent the extra frame will not
>>>>>> be pushed down if display interface is down so that crtc->active
>>>>>> will not be set neither. This will fail the conditions checking
>>>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>>>> at dp_bridge_disable() prevented.
>>>>>
>>>>> I must admit I had troubles parsing this description. However if I
>>>>> got you right, I think the check that the main link clock is
>>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle() would be
>>>>> a better fix.
>>>>
>>>> Originally, thats what was posted
>>>> https://patchwork.freedesktop.org/patch/496984/.
>>>
>>> This patch is also not so correct from my POV. It checks for the hpd
>>> status, while in reality it should check for main link clocks being
>>> enabled.
>>>
>>
>> We can push another fix to check for the clk state instead of the hpd
>> status. But I must say we are again just masking something which the
>> fwk should have avoided isnt it?
>>
>> As per the doc in the include/drm/drm_bridge.h it says,
>>
>> "*
>> * The bridge can assume that the display pipe (i.e. clocks and timing
>> * signals) feeding it is still running when this callback is called.
>> *"
>
> Yes, that's what I meant about this chunk begging to go to the core. In
> my opinion, if we are talking about the disconnected sinks, it is the
> framework who should disallow submitting the frames to the disconnected
> sinks.
>
>>
>> By adding an extra layers of protection in the driver, we are just
>> avoiding another issue but the commit should not have been issued in
>> the first place.
>>
>> So shouldnt we do both then? That is add protection to check if clock
>> is ON and also, reject commits when display is disconnected.
>>
>>>>
>>>> Then it seemed like we were just protecting against an issue in the
>>>> framework which was allowing the frames to be pushed even after the
>>>> display was disconnected. The DP driver did send out the disconnect
>>>> event correctly and as per the logs, this frame came down after that
>>>> and the DRM fwk did allow it.
>>>>
>>>> So after discussing on IRC with Rob, we came up with this approach that
>>>> if the display is not connected, then atomic_check should fail. That
>>>> way the commit will not happen.
>>>>
>>>> Just seemed a bit cleaner instead of adding all our protections.
>>>
>>> The check to fail atomic_check if display is not connected seems out
>>> of place. In its current way it begs go to the upper layer,
>>> forbidding using disconnected sinks for all the drivers. There is
>>> nothing special in the MSM DP driver with respect to the HPD events
>>> processing and failing atomic_check() based on that.
>>>
>>
>> Why all the drivers? This is only for MSM DP bridge.
>
> Yes, we change the MSM DRM driver. But the check is generic enough. I'm
> not actually insisting on pushing the check to the core, just trying to
> understand the real cause here.
>
>>
I actually wanted to push this to the core and thats what I had
originally asked on IRC because it does seem to be generic enough that
it should belong to the core but after discussion with Rob on freedreno,
he felt this was a better approach because for some of the legacy
connectors like VGA, this need not belong to the DRM core, hence we went
with this approach.
>>>>
>>>>>
>>>>>>
>>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>>>> sp : ffffffc01092b6a0
>>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>> Call trace:
>>>>>> dump_backtrace.part.0+0xbc/0xe4
>>>>>> show_stack+0x24/0x70
>>>>>> dump_stack_lvl+0x68/0x84
>>>>>> dump_stack+0x18/0x34
>>>>>> panic+0x14c/0x32c
>>>>>> nmi_panic+0x58/0x7c
>>>>>> arm64_serror_panic+0x78/0x84
>>>>>> do_serror+0x40/0x64
>>>>>> el1h_64_error_handler+0x30/0x48
>>>>>> el1h_64_error+0x68/0x6c
>>>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>>>> _raw_spin_lock_irqsave+0x38/0x4c
>
> You know, after re-reading the trace, I could not help but notice that
> the issue seems to be related to completion/timer/spinlock memory
> becoming unavailable rather than disabling the main link clock.
> See, the SError comes in the spin_lock path, not during register read.
>
> Thus I think the commit message is a bit misleading.
>
No, this issue is due to unclocked access. Please check this part of the
stack:
>>>>>> wait_for_completion_timeout+0x2c/0x54
>>>>>> dp_ctrl_push_idle+0x40/0x88
>>>>>> dp_bridge_disable+0x24/0x30
>>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>>>> commit_tail+0x80/0x108
>>>>>> drm_atomic_helper_commit+0x118/0x11c
>>>>>> drm_atomic_commit+0xb4/0xe0
>>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>>>> drm_client_modeset_commit+0x3c/0x64
> Can we please get a trace checking which calls were actually made for
> the dp bridge and if the dp/dp->ctrl memory pointers are correct?
>
> I do not see the dp_display_disable() being called. Maybe I just missed
> the call.
>
Yes it is called, please refer to the above part of the stack that I
have pasted.
>
>>>>>> lock_timer_base+0x40/0x78
>>>>>> __mod_timer+0xf4/0x25c
>>>>>> schedule_timeout+0xd4/0xfc
>>>>>> __wait_for_common+0xac/0x140
>>>>>> wait_for_completion_timeout+0x2c/0x54
>>>>>> dp_ctrl_push_idle+0x40/0x88
>>>>>> dp_bridge_disable+0x24/0x30
>>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>>>> commit_tail+0x80/0x108
>>>>>> drm_atomic_helper_commit+0x118/0x11c
>>>>>> drm_atomic_commit+0xb4/0xe0
>>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>>>> drm_client_modeset_commit+0x3c/0x64
>>>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
>>>>>> drm_fb_helper_set_par+0x74/0x80
>>>>>> drm_fb_helper_hotplug_event+0xdc/0xe0
>>>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
>>>>>> drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
>>>>>> drm_fb_helper_lastclose+0x20/0x2c
>>>>>> drm_lastclose+0x44/0x6c
>>>>>> drm_release+0x88/0xd4
>>>>>> __fput+0x104/0x220
>>>>>> ____fput+0x1c/0x28
>>>>>> task_work_run+0x8c/0x100
>>>>>> do_exit+0x450/0x8d0
>>>>>> do_group_exit+0x40/0xac
>>>>>> __wake_up_parent+0x0/0x38
>>>>>> invoke_syscall+0x84/0x11c
>>>>>> el0_svc_common.constprop.0+0xb8/0xe4
>>>>>> do_el0_svc+0x8c/0xb8
>>>>>> el0_svc+0x2c/0x54
>>>>>> el0t_64_sync_handler+0x120/0x1c0
>>>>>> el0t_64_sync+0x190/0x194
>>>>>> SMP: stopping secondary CPUs
>>>>>> Kernel Offset: 0x128e800000 from 0xffffffc008000000
>>>>>> PHYS_OFFSET: 0x80000000
>>>>>> CPU features: 0x800,00c2a015,19801c82
>>>>>> Memory Limit: none
>>>>>>
>>>>>> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for
>>>>>> display enable and disable")
>>>>>> Reported-by: Leonard Lausen <leonard@lausen.nl>
>>>>>> Suggested-by: Rob Clark <robdclark@gmail.com>
>>>>>> Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
>>>>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>>>>>> ---
>>>>>> drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
>>>>>> 1 file changed, 23 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>> b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>> index 6df25f7..c682588 100644
>>>>>> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>> @@ -31,6 +31,25 @@ static enum drm_connector_status
>>>>>> dp_bridge_detect(struct drm_bridge *bridge)
>>>>>> connector_status_disconnected;
>>>>>> }
>>>>>> +static int dp_bridge_atomic_check(struct drm_bridge *bridge,
>>>>>> + struct drm_bridge_state *bridge_state,
>>>>>> + struct drm_crtc_state *crtc_state,
>>>>>> + struct drm_connector_state *conn_state)
>>>>>> +{
>>>>>> + struct msm_dp *dp;
>>>>>> +
>>>>>> + dp = to_dp_bridge(bridge)->dp_display;
>>>>>> +
>>>>>> + drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
>>>>>> + (dp->is_connected) ? "true" : "false");
>>>>>> +
>>>>>> + if (bridge->ops & DRM_BRIDGE_OP_HPD)
>>>>>> + return (dp->is_connected) ? 0 : -ENOTCONN;
>>>
>>> This raises questions if this will work for the configurations when
>>> other bridge is used for HPD events.
>>>
>>> Let's not mix the levels of processing. If we should not disable the
>>> link because it is already disabled, let's just do so rather than
>>> failing the atomic_check().
>>>
>>
>> This is only for MSM DP's bridge. If we use another bridge which is
>> capable of handling its own HPD, then that time MSM DP's bridge
>> shouldnt set this flag.
>
> Not quite. The bridges set the ops to describe the ops that they support
> themselves. Then the drm_bridge_connectors selects the bridge handling
> hpd, etc. So the DRM_BRIDGE_OP_HPD is always set for DP sources. But the
> question is quite the opposite: if we have the next bridge (e.g. the
> usb-c-connector or the display-connector), will the is_connected field
> be set correctly?
>
>>
>> We can even replace this check with just checking if connector_type is
>> DP but that would again open the discussion of having DP/eDP specific
>> checks so we did it this way.
>>
>>
>>>>>> +
>>>>>> + return 0;
>>>>>> +}
>>>>>> +
>>>>>> +
>>>>>> /**
>>>>>> * dp_bridge_get_modes - callback to add drm modes via
>>>>>> drm_mode_probed_add()
>>>>>> * @bridge: Poiner to drm bridge
>>>>>> @@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct drm_bridge
>>>>>> *bridge, struct drm_connector *
>>>>>> }
>>>>>> static const struct drm_bridge_funcs dp_bridge_ops = {
>>>>>> + .atomic_duplicate_state =
>>>>>> drm_atomic_helper_bridge_duplicate_state,
>>>>>> + .atomic_destroy_state =
>>>>>> drm_atomic_helper_bridge_destroy_state,
>>>>>> + .atomic_reset = drm_atomic_helper_bridge_reset,
>>>>>> .enable = dp_bridge_enable,
>>>>>> .disable = dp_bridge_disable,
>>>>>> .post_disable = dp_bridge_post_disable,
>>>>>> @@ -68,6 +90,7 @@ static const struct drm_bridge_funcs
>>>>>> dp_bridge_ops = {
>>>>>> .mode_valid = dp_bridge_mode_valid,
>>>>>> .get_modes = dp_bridge_get_modes,
>>>>>> .detect = dp_bridge_detect,
>>>>>> + .atomic_check = dp_bridge_atomic_check,
>>>>>> };
>>>>>> struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display,
>>>>>> struct drm_device *dev,
>>>>>
>>>
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-23 22:07 ` Abhinav Kumar
@ 2022-08-23 22:18 ` Abhinav Kumar
2022-08-23 22:41 ` Dmitry Baryshkov
1 sibling, 0 replies; 14+ messages in thread
From: Abhinav Kumar @ 2022-08-23 22:18 UTC (permalink / raw)
To: Dmitry Baryshkov, Kuogee Hsieh, robdclark, sean, swboyd,
dianders, vkoul, daniel, airlied, agross, bjorn.andersson
Cc: quic_sbillaka, linux-arm-msm, linux-kernel, dri-devel,
quic_aravindh, freedreno
Sorry missed one response,
On 8/23/2022 3:07 PM, Abhinav Kumar wrote:
>
>
> On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
>> On 22/08/2022 20:32, Abhinav Kumar wrote:
>>>
>>>
>>> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
>>>> On 22/08/2022 19:38, Abhinav Kumar wrote:
>>>>> Hi Dmitry
>>>>>
>>>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>>>>>>> both disable crtc is required and crtc->active is set before pushing
>>>>>>> a new frame downstream.
>>>>>>>
>>>>>>> There is a rare case that user space display manager issue an extra
>>>>>>> screen update immediately followed by close DRM device while down
>>>>>>> stream display interface is disabled. This extra screen update will
>>>>>>> timeout due to the downstream interface is disabled but will cause
>>>>>>> crtc->active be set. Hence the followed commit_tails() called by
>>>>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
>>>>>>> conditions checking even downstream interface is disabled.
>>>>>>> This cause the crash to happen at dp_bridge_disable() due to it
>>>>>>> trying
>>>>>>> to access the main link register to push the idle pattern out
>>>>>>> while main
>>>>>>> link clocks is disabled.
>>>>>>>
>>>>>>> This patch adds atomic_check to prevent the extra frame will not
>>>>>>> be pushed down if display interface is down so that crtc->active
>>>>>>> will not be set neither. This will fail the conditions checking
>>>>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>>>>> at dp_bridge_disable() prevented.
>>>>>>
>>>>>> I must admit I had troubles parsing this description. However if I
>>>>>> got you right, I think the check that the main link clock is
>>>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle() would be
>>>>>> a better fix.
>>>>>
>>>>> Originally, thats what was posted
>>>>> https://patchwork.freedesktop.org/patch/496984/.
>>>>
>>>> This patch is also not so correct from my POV. It checks for the hpd
>>>> status, while in reality it should check for main link clocks being
>>>> enabled.
>>>>
>>>
>>> We can push another fix to check for the clk state instead of the hpd
>>> status. But I must say we are again just masking something which the
>>> fwk should have avoided isnt it?
>>>
>>> As per the doc in the include/drm/drm_bridge.h it says,
>>>
>>> "*
>>> * The bridge can assume that the display pipe (i.e. clocks and timing
>>> * signals) feeding it is still running when this callback is called.
>>> *"
>>
>> Yes, that's what I meant about this chunk begging to go to the core.
>> In my opinion, if we are talking about the disconnected sinks, it is
>> the framework who should disallow submitting the frames to the
>> disconnected sinks.
>>
>>>
>>> By adding an extra layers of protection in the driver, we are just
>>> avoiding another issue but the commit should not have been issued in
>>> the first place.
>>>
>>> So shouldnt we do both then? That is add protection to check if clock
>>> is ON and also, reject commits when display is disconnected.
>>>
>>>>>
>>>>> Then it seemed like we were just protecting against an issue in the
>>>>> framework which was allowing the frames to be pushed even after the
>>>>> display was disconnected. The DP driver did send out the disconnect
>>>>> event correctly and as per the logs, this frame came down after
>>>>> that and the DRM fwk did allow it.
>>>>>
>>>>> So after discussing on IRC with Rob, we came up with this approach
>>>>> that
>>>>> if the display is not connected, then atomic_check should fail.
>>>>> That way the commit will not happen.
>>>>>
>>>>> Just seemed a bit cleaner instead of adding all our protections.
>>>>
>>>> The check to fail atomic_check if display is not connected seems out
>>>> of place. In its current way it begs go to the upper layer,
>>>> forbidding using disconnected sinks for all the drivers. There is
>>>> nothing special in the MSM DP driver with respect to the HPD events
>>>> processing and failing atomic_check() based on that.
>>>>
>>>
>>> Why all the drivers? This is only for MSM DP bridge.
>>
>> Yes, we change the MSM DRM driver. But the check is generic enough.
>> I'm not actually insisting on pushing the check to the core, just
>> trying to understand the real cause here.
>>
>>>
>
> I actually wanted to push this to the core and thats what I had
> originally asked on IRC because it does seem to be generic enough that
> it should belong to the core but after discussion with Rob on freedreno,
> he felt this was a better approach because for some of the legacy
> connectors like VGA, this need not belong to the DRM core, hence we went
> with this approach.
>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>>>>> sp : ffffffc01092b6a0
>>>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>>>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>>>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>>>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>>>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>>>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>>>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>>>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>>>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>>>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>>>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>> Call trace:
>>>>>>> dump_backtrace.part.0+0xbc/0xe4
>>>>>>> show_stack+0x24/0x70
>>>>>>> dump_stack_lvl+0x68/0x84
>>>>>>> dump_stack+0x18/0x34
>>>>>>> panic+0x14c/0x32c
>>>>>>> nmi_panic+0x58/0x7c
>>>>>>> arm64_serror_panic+0x78/0x84
>>>>>>> do_serror+0x40/0x64
>>>>>>> el1h_64_error_handler+0x30/0x48
>>>>>>> el1h_64_error+0x68/0x6c
>>>>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>> _raw_spin_lock_irqsave+0x38/0x4c
>>
>> You know, after re-reading the trace, I could not help but notice that
>> the issue seems to be related to completion/timer/spinlock memory
>> becoming unavailable rather than disabling the main link clock.
>> See, the SError comes in the spin_lock path, not during register read.
>>
>> Thus I think the commit message is a bit misleading.
>>
>
> No, this issue is due to unclocked access. Please check this part of the
> stack:
>
> >>>>>> wait_for_completion_timeout+0x2c/0x54
> >>>>>> dp_ctrl_push_idle+0x40/0x88
> >>>>>> dp_bridge_disable+0x24/0x30
> >>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
> >>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
> >>>>>> msm_atomic_commit_tail+0x1d0/0x374
> >>>>>> commit_tail+0x80/0x108
> >>>>>> drm_atomic_helper_commit+0x118/0x11c
> >>>>>> drm_atomic_commit+0xb4/0xe0
> >>>>>> drm_client_modeset_commit_atomic+0x184/0x224
> >>>>>> drm_client_modeset_commit_locked+0x58/0x160
> >>>>>> drm_client_modeset_commit+0x3c/0x64
>
>> Can we please get a trace checking which calls were actually made for
>> the dp bridge and if the dp/dp->ctrl memory pointers are correct?
>>
>> I do not see the dp_display_disable() being called. Maybe I just
>> missed the call.
>>
>
> Yes it is called, please refer to the above part of the stack that I
> have pasted.
>
>>
>>>>>>> lock_timer_base+0x40/0x78
>>>>>>> __mod_timer+0xf4/0x25c
>>>>>>> schedule_timeout+0xd4/0xfc
>>>>>>> __wait_for_common+0xac/0x140
>>>>>>> wait_for_completion_timeout+0x2c/0x54
>>>>>>> dp_ctrl_push_idle+0x40/0x88
>>>>>>> dp_bridge_disable+0x24/0x30
>>>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>>>>> commit_tail+0x80/0x108
>>>>>>> drm_atomic_helper_commit+0x118/0x11c
>>>>>>> drm_atomic_commit+0xb4/0xe0
>>>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>>>>> drm_client_modeset_commit+0x3c/0x64
>>>>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x98/0xac
>>>>>>> drm_fb_helper_set_par+0x74/0x80
>>>>>>> drm_fb_helper_hotplug_event+0xdc/0xe0
>>>>>>> __drm_fb_helper_restore_fbdev_mode_unlocked+0x7c/0xac
>>>>>>> drm_fb_helper_restore_fbdev_mode_unlocked+0x20/0x2c
>>>>>>> drm_fb_helper_lastclose+0x20/0x2c
>>>>>>> drm_lastclose+0x44/0x6c
>>>>>>> drm_release+0x88/0xd4
>>>>>>> __fput+0x104/0x220
>>>>>>> ____fput+0x1c/0x28
>>>>>>> task_work_run+0x8c/0x100
>>>>>>> do_exit+0x450/0x8d0
>>>>>>> do_group_exit+0x40/0xac
>>>>>>> __wake_up_parent+0x0/0x38
>>>>>>> invoke_syscall+0x84/0x11c
>>>>>>> el0_svc_common.constprop.0+0xb8/0xe4
>>>>>>> do_el0_svc+0x8c/0xb8
>>>>>>> el0_svc+0x2c/0x54
>>>>>>> el0t_64_sync_handler+0x120/0x1c0
>>>>>>> el0t_64_sync+0x190/0x194
>>>>>>> SMP: stopping secondary CPUs
>>>>>>> Kernel Offset: 0x128e800000 from 0xffffffc008000000
>>>>>>> PHYS_OFFSET: 0x80000000
>>>>>>> CPU features: 0x800,00c2a015,19801c82
>>>>>>> Memory Limit: none
>>>>>>>
>>>>>>> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for
>>>>>>> display enable and disable")
>>>>>>> Reported-by: Leonard Lausen <leonard@lausen.nl>
>>>>>>> Suggested-by: Rob Clark <robdclark@gmail.com>
>>>>>>> Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
>>>>>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>>>>>>> ---
>>>>>>> drivers/gpu/drm/msm/dp/dp_drm.c | 23 +++++++++++++++++++++++
>>>>>>> 1 file changed, 23 insertions(+)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>>> b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>>> index 6df25f7..c682588 100644
>>>>>>> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>>> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>>>>>>> @@ -31,6 +31,25 @@ static enum drm_connector_status
>>>>>>> dp_bridge_detect(struct drm_bridge *bridge)
>>>>>>> connector_status_disconnected;
>>>>>>> }
>>>>>>> +static int dp_bridge_atomic_check(struct drm_bridge *bridge,
>>>>>>> + struct drm_bridge_state *bridge_state,
>>>>>>> + struct drm_crtc_state *crtc_state,
>>>>>>> + struct drm_connector_state *conn_state)
>>>>>>> +{
>>>>>>> + struct msm_dp *dp;
>>>>>>> +
>>>>>>> + dp = to_dp_bridge(bridge)->dp_display;
>>>>>>> +
>>>>>>> + drm_dbg_dp(dp->drm_dev, "is_connected = %s\n",
>>>>>>> + (dp->is_connected) ? "true" : "false");
>>>>>>> +
>>>>>>> + if (bridge->ops & DRM_BRIDGE_OP_HPD)
>>>>>>> + return (dp->is_connected) ? 0 : -ENOTCONN;
>>>>
>>>> This raises questions if this will work for the configurations when
>>>> other bridge is used for HPD events.
>>>>
>>>> Let's not mix the levels of processing. If we should not disable the
>>>> link because it is already disabled, let's just do so rather than
>>>> failing the atomic_check().
>>>>
>>>
>>> This is only for MSM DP's bridge. If we use another bridge which is
>>> capable of handling its own HPD, then that time MSM DP's bridge
>>> shouldnt set this flag.
>>
>> Not quite. The bridges set the ops to describe the ops that they
>> support themselves. Then the drm_bridge_connectors selects the bridge
>> handling hpd, etc. So the DRM_BRIDGE_OP_HPD is always set for DP
>> sources. But the question is quite the opposite: if we have the next
>> bridge (e.g. the usb-c-connector or the display-connector), will the
>> is_connected field be set correctly?
>>
Ah I got your concern now, I would say Yes because looking at Bjorn's
change https://patchwork.freedesktop.org/patch/496925/, I can see that
the next bridge would call into dp_bridge_hpd_notify() which calls
dp_display_send_hpd_notification() finally setting
dp->dp_display.is_connected to true.
>>>
>>> We can even replace this check with just checking if connector_type
>>> is DP but that would again open the discussion of having DP/eDP
>>> specific checks so we did it this way.
>>>
>>>
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +
>>>>>>> /**
>>>>>>> * dp_bridge_get_modes - callback to add drm modes via
>>>>>>> drm_mode_probed_add()
>>>>>>> * @bridge: Poiner to drm bridge
>>>>>>> @@ -61,6 +80,9 @@ static int dp_bridge_get_modes(struct
>>>>>>> drm_bridge *bridge, struct drm_connector *
>>>>>>> }
>>>>>>> static const struct drm_bridge_funcs dp_bridge_ops = {
>>>>>>> + .atomic_duplicate_state =
>>>>>>> drm_atomic_helper_bridge_duplicate_state,
>>>>>>> + .atomic_destroy_state =
>>>>>>> drm_atomic_helper_bridge_destroy_state,
>>>>>>> + .atomic_reset = drm_atomic_helper_bridge_reset,
>>>>>>> .enable = dp_bridge_enable,
>>>>>>> .disable = dp_bridge_disable,
>>>>>>> .post_disable = dp_bridge_post_disable,
>>>>>>> @@ -68,6 +90,7 @@ static const struct drm_bridge_funcs
>>>>>>> dp_bridge_ops = {
>>>>>>> .mode_valid = dp_bridge_mode_valid,
>>>>>>> .get_modes = dp_bridge_get_modes,
>>>>>>> .detect = dp_bridge_detect,
>>>>>>> + .atomic_check = dp_bridge_atomic_check,
>>>>>>> };
>>>>>>> struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display,
>>>>>>> struct drm_device *dev,
>>>>>>
>>>>
>>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-23 22:07 ` Abhinav Kumar
2022-08-23 22:18 ` Abhinav Kumar
@ 2022-08-23 22:41 ` Dmitry Baryshkov
2022-08-23 22:59 ` Abhinav Kumar
1 sibling, 1 reply; 14+ messages in thread
From: Dmitry Baryshkov @ 2022-08-23 22:41 UTC (permalink / raw)
To: Abhinav Kumar
Cc: freedreno, quic_sbillaka, dianders, airlied, linux-arm-msm,
dri-devel, swboyd, vkoul, agross, bjorn.andersson, quic_aravindh,
Kuogee Hsieh, sean, linux-kernel
On Wed, 24 Aug 2022 at 01:07, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote:
> On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
> > On 22/08/2022 20:32, Abhinav Kumar wrote:
> >>
> >>
> >> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
> >>> On 22/08/2022 19:38, Abhinav Kumar wrote:
> >>>> Hi Dmitry
> >>>>
> >>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
> >>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
> >>>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
> >>>>>> both disable crtc is required and crtc->active is set before pushing
> >>>>>> a new frame downstream.
> >>>>>>
> >>>>>> There is a rare case that user space display manager issue an extra
> >>>>>> screen update immediately followed by close DRM device while down
> >>>>>> stream display interface is disabled. This extra screen update will
> >>>>>> timeout due to the downstream interface is disabled but will cause
> >>>>>> crtc->active be set. Hence the followed commit_tails() called by
> >>>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
> >>>>>> conditions checking even downstream interface is disabled.
> >>>>>> This cause the crash to happen at dp_bridge_disable() due to it
> >>>>>> trying
> >>>>>> to access the main link register to push the idle pattern out
> >>>>>> while main
> >>>>>> link clocks is disabled.
> >>>>>>
> >>>>>> This patch adds atomic_check to prevent the extra frame will not
> >>>>>> be pushed down if display interface is down so that crtc->active
> >>>>>> will not be set neither. This will fail the conditions checking
> >>>>>> of disabling down stream crtc/encoder/bridge which prevent
> >>>>>> drm_release() from calling dp_bridge_disable() so that crash
> >>>>>> at dp_bridge_disable() prevented.
> >>>>>
> >>>>> I must admit I had troubles parsing this description. However if I
> >>>>> got you right, I think the check that the main link clock is
> >>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle() would be
> >>>>> a better fix.
> >>>>
> >>>> Originally, thats what was posted
> >>>> https://patchwork.freedesktop.org/patch/496984/.
> >>>
> >>> This patch is also not so correct from my POV. It checks for the hpd
> >>> status, while in reality it should check for main link clocks being
> >>> enabled.
> >>>
> >>
> >> We can push another fix to check for the clk state instead of the hpd
> >> status. But I must say we are again just masking something which the
> >> fwk should have avoided isnt it?
> >>
> >> As per the doc in the include/drm/drm_bridge.h it says,
> >>
> >> "*
> >> * The bridge can assume that the display pipe (i.e. clocks and timing
> >> * signals) feeding it is still running when this callback is called.
> >> *"
> >
> > Yes, that's what I meant about this chunk begging to go to the core. In
> > my opinion, if we are talking about the disconnected sinks, it is the
> > framework who should disallow submitting the frames to the disconnected
> > sinks.
> >
> >>
> >> By adding an extra layers of protection in the driver, we are just
> >> avoiding another issue but the commit should not have been issued in
> >> the first place.
> >>
> >> So shouldnt we do both then? That is add protection to check if clock
> >> is ON and also, reject commits when display is disconnected.
> >>
> >>>>
> >>>> Then it seemed like we were just protecting against an issue in the
> >>>> framework which was allowing the frames to be pushed even after the
> >>>> display was disconnected. The DP driver did send out the disconnect
> >>>> event correctly and as per the logs, this frame came down after that
> >>>> and the DRM fwk did allow it.
> >>>>
> >>>> So after discussing on IRC with Rob, we came up with this approach that
> >>>> if the display is not connected, then atomic_check should fail. That
> >>>> way the commit will not happen.
> >>>>
> >>>> Just seemed a bit cleaner instead of adding all our protections.
> >>>
> >>> The check to fail atomic_check if display is not connected seems out
> >>> of place. In its current way it begs go to the upper layer,
> >>> forbidding using disconnected sinks for all the drivers. There is
> >>> nothing special in the MSM DP driver with respect to the HPD events
> >>> processing and failing atomic_check() based on that.
> >>>
> >>
> >> Why all the drivers? This is only for MSM DP bridge.
> >
> > Yes, we change the MSM DRM driver. But the check is generic enough. I'm
> > not actually insisting on pushing the check to the core, just trying to
> > understand the real cause here.
> >
> >>
>
> I actually wanted to push this to the core and thats what I had
> originally asked on IRC because it does seem to be generic enough that
> it should belong to the core but after discussion with Rob on freedreno,
> he felt this was a better approach because for some of the legacy
> connectors like VGA, this need not belong to the DRM core, hence we went
> with this approach.
It might be better to whitelist such connectors (S-VIDEO/composite
comes to my mind rather than VGA).
> >>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
> >>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
> >>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
> >>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> >>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
> >>>>>> lr : do_raw_spin_lock+0xa4/0xdc
> >>>>>> sp : ffffffc01092b6a0
> >>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
> >>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
> >>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
> >>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
> >>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
> >>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
> >>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
> >>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
> >>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
> >>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
> >>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
> >>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
> >>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
> >>>>>> Call trace:
> >>>>>> dump_backtrace.part.0+0xbc/0xe4
> >>>>>> show_stack+0x24/0x70
> >>>>>> dump_stack_lvl+0x68/0x84
> >>>>>> dump_stack+0x18/0x34
> >>>>>> panic+0x14c/0x32c
> >>>>>> nmi_panic+0x58/0x7c
> >>>>>> arm64_serror_panic+0x78/0x84
> >>>>>> do_serror+0x40/0x64
> >>>>>> el1h_64_error_handler+0x30/0x48
> >>>>>> el1h_64_error+0x68/0x6c
> >>>>>> __cmpxchg_case_acq_32+0x14/0x2c
> >>>>>> _raw_spin_lock_irqsave+0x38/0x4c
> >
> > You know, after re-reading the trace, I could not help but notice that
> > the issue seems to be related to completion/timer/spinlock memory
> > becoming unavailable rather than disabling the main link clock.
> > See, the SError comes in the spin_lock path, not during register read.
> >
> > Thus I think the commit message is a bit misleading.
> >
>
> No, this issue is due to unclocked access. Please check this part of the
> stack:
Well, if it were for the unlocked access, we would see SError on the
register access, wouldn't we? However in this case the SError comes
from the raw spinlock code.
> >>>>>> wait_for_completion_timeout+0x2c/0x54
> >>>>>> dp_ctrl_push_idle+0x40/0x88
> >>>>>> dp_bridge_disable+0x24/0x30
> >>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
> >>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
> >>>>>> msm_atomic_commit_tail+0x1d0/0x374
> >>>>>> commit_tail+0x80/0x108
> >>>>>> drm_atomic_helper_commit+0x118/0x11c
> >>>>>> drm_atomic_commit+0xb4/0xe0
> >>>>>> drm_client_modeset_commit_atomic+0x184/0x224
> >>>>>> drm_client_modeset_commit_locked+0x58/0x160
> >>>>>> drm_client_modeset_commit+0x3c/0x64
>
> > Can we please get a trace checking which calls were actually made for
> > the dp bridge and if the dp/dp->ctrl memory pointers are correct?
> >
> > I do not see the dp_display_disable() being called. Maybe I just missed
> > the call.
> >
>
> Yes it is called, please refer to the above part of the stack that I
> have pasted.
The stacktrace mentions dp_bridge_disable(), not dp_display_disable()
(which I asked for).
--
With best wishes
Dmitry
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-23 22:41 ` Dmitry Baryshkov
@ 2022-08-23 22:59 ` Abhinav Kumar
2022-08-24 8:25 ` Dmitry Baryshkov
0 siblings, 1 reply; 14+ messages in thread
From: Abhinav Kumar @ 2022-08-23 22:59 UTC (permalink / raw)
To: Dmitry Baryshkov
Cc: freedreno, quic_sbillaka, dianders, airlied, linux-arm-msm,
dri-devel, swboyd, vkoul, agross, bjorn.andersson, quic_aravindh,
Kuogee Hsieh, sean, linux-kernel
On 8/23/2022 3:41 PM, Dmitry Baryshkov wrote:
> On Wed, 24 Aug 2022 at 01:07, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote:
>> On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
>>> On 22/08/2022 20:32, Abhinav Kumar wrote:
>>>>
>>>>
>>>> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
>>>>> On 22/08/2022 19:38, Abhinav Kumar wrote:
>>>>>> Hi Dmitry
>>>>>>
>>>>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>>>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>>>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>>>>>>>> both disable crtc is required and crtc->active is set before pushing
>>>>>>>> a new frame downstream.
>>>>>>>>
>>>>>>>> There is a rare case that user space display manager issue an extra
>>>>>>>> screen update immediately followed by close DRM device while down
>>>>>>>> stream display interface is disabled. This extra screen update will
>>>>>>>> timeout due to the downstream interface is disabled but will cause
>>>>>>>> crtc->active be set. Hence the followed commit_tails() called by
>>>>>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
>>>>>>>> conditions checking even downstream interface is disabled.
>>>>>>>> This cause the crash to happen at dp_bridge_disable() due to it
>>>>>>>> trying
>>>>>>>> to access the main link register to push the idle pattern out
>>>>>>>> while main
>>>>>>>> link clocks is disabled.
>>>>>>>>
>>>>>>>> This patch adds atomic_check to prevent the extra frame will not
>>>>>>>> be pushed down if display interface is down so that crtc->active
>>>>>>>> will not be set neither. This will fail the conditions checking
>>>>>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>>>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>>>>>> at dp_bridge_disable() prevented.
>>>>>>>
>>>>>>> I must admit I had troubles parsing this description. However if I
>>>>>>> got you right, I think the check that the main link clock is
>>>>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle() would be
>>>>>>> a better fix.
>>>>>>
>>>>>> Originally, thats what was posted
>>>>>> https://patchwork.freedesktop.org/patch/496984/.
>>>>>
>>>>> This patch is also not so correct from my POV. It checks for the hpd
>>>>> status, while in reality it should check for main link clocks being
>>>>> enabled.
>>>>>
>>>>
>>>> We can push another fix to check for the clk state instead of the hpd
>>>> status. But I must say we are again just masking something which the
>>>> fwk should have avoided isnt it?
>>>>
>>>> As per the doc in the include/drm/drm_bridge.h it says,
>>>>
>>>> "*
>>>> * The bridge can assume that the display pipe (i.e. clocks and timing
>>>> * signals) feeding it is still running when this callback is called.
>>>> *"
>>>
>>> Yes, that's what I meant about this chunk begging to go to the core. In
>>> my opinion, if we are talking about the disconnected sinks, it is the
>>> framework who should disallow submitting the frames to the disconnected
>>> sinks.
>>>
>>>>
>>>> By adding an extra layers of protection in the driver, we are just
>>>> avoiding another issue but the commit should not have been issued in
>>>> the first place.
>>>>
>>>> So shouldnt we do both then? That is add protection to check if clock
>>>> is ON and also, reject commits when display is disconnected.
>>>>
>>>>>>
>>>>>> Then it seemed like we were just protecting against an issue in the
>>>>>> framework which was allowing the frames to be pushed even after the
>>>>>> display was disconnected. The DP driver did send out the disconnect
>>>>>> event correctly and as per the logs, this frame came down after that
>>>>>> and the DRM fwk did allow it.
>>>>>>
>>>>>> So after discussing on IRC with Rob, we came up with this approach that
>>>>>> if the display is not connected, then atomic_check should fail. That
>>>>>> way the commit will not happen.
>>>>>>
>>>>>> Just seemed a bit cleaner instead of adding all our protections.
>>>>>
>>>>> The check to fail atomic_check if display is not connected seems out
>>>>> of place. In its current way it begs go to the upper layer,
>>>>> forbidding using disconnected sinks for all the drivers. There is
>>>>> nothing special in the MSM DP driver with respect to the HPD events
>>>>> processing and failing atomic_check() based on that.
>>>>>
>>>>
>>>> Why all the drivers? This is only for MSM DP bridge.
>>>
>>> Yes, we change the MSM DRM driver. But the check is generic enough. I'm
>>> not actually insisting on pushing the check to the core, just trying to
>>> understand the real cause here.
>>>
>>>>
>>
>> I actually wanted to push this to the core and thats what I had
>> originally asked on IRC because it does seem to be generic enough that
>> it should belong to the core but after discussion with Rob on freedreno,
>> he felt this was a better approach because for some of the legacy
>> connectors like VGA, this need not belong to the DRM core, hence we went
>> with this approach.
>
> It might be better to whitelist such connectors (S-VIDEO/composite
> comes to my mind rather than VGA).
I am fine with that approach, if Rob is onboard with that.
>
>>>>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>>>>>> sp : ffffffc01092b6a0
>>>>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>>>>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>>>>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>>>>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>>>>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>>>>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>>>>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>>>>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>>>>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>>>>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>>>>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>> Call trace:
>>>>>>>> dump_backtrace.part.0+0xbc/0xe4
>>>>>>>> show_stack+0x24/0x70
>>>>>>>> dump_stack_lvl+0x68/0x84
>>>>>>>> dump_stack+0x18/0x34
>>>>>>>> panic+0x14c/0x32c
>>>>>>>> nmi_panic+0x58/0x7c
>>>>>>>> arm64_serror_panic+0x78/0x84
>>>>>>>> do_serror+0x40/0x64
>>>>>>>> el1h_64_error_handler+0x30/0x48
>>>>>>>> el1h_64_error+0x68/0x6c
>>>>>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>> _raw_spin_lock_irqsave+0x38/0x4c
>>>
>>> You know, after re-reading the trace, I could not help but notice that
>>> the issue seems to be related to completion/timer/spinlock memory
>>> becoming unavailable rather than disabling the main link clock.
>>> See, the SError comes in the spin_lock path, not during register read.
>>>
>>> Thus I think the commit message is a bit misleading.
>>>
>>
>> No, this issue is due to unclocked access. Please check this part of the
>> stack:
>
> Well, if it were for the unlocked access, we would see SError on the
> register access, wouldn't we? However in this case the SError comes
> from the raw spinlock code.
This is not uncommon. With unclocked access, we have seen in the past
that sometimes the stack is off by one line. The fact that this issue
got resolved even with the older version of the patch
https://patchwork.freedesktop.org/patch/496984/ is pointing towards an
unclocked access and not the dp/dp->ctrl memory pointers.
>
>> >>>>>> wait_for_completion_timeout+0x2c/0x54
>> >>>>>> dp_ctrl_push_idle+0x40/0x88
>> >>>>>> dp_bridge_disable+0x24/0x30
>> >>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>> >>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>> >>>>>> msm_atomic_commit_tail+0x1d0/0x374
>> >>>>>> commit_tail+0x80/0x108
>> >>>>>> drm_atomic_helper_commit+0x118/0x11c
>> >>>>>> drm_atomic_commit+0xb4/0xe0
>> >>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>> >>>>>> drm_client_modeset_commit_locked+0x58/0x160
>> >>>>>> drm_client_modeset_commit+0x3c/0x64
>>
>>> Can we please get a trace checking which calls were actually made for
>>> the dp bridge and if the dp/dp->ctrl memory pointers are correct?
>>>
>>> I do not see the dp_display_disable() being called. Maybe I just missed
>>> the call.
>>>
>>
>> Yes it is called, please refer to the above part of the stack that I
>> have pasted.
>
> The stacktrace mentions dp_bridge_disable(), not dp_display_disable()
> (which I asked for).
>
So whats happening here is the crash is happening in dp_bridge_disable().
dp_display_disable() is called from post_disable() thats why it doesnt
show up in the stack.
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-23 22:59 ` Abhinav Kumar
@ 2022-08-24 8:25 ` Dmitry Baryshkov
2022-08-24 19:16 ` Abhinav Kumar
0 siblings, 1 reply; 14+ messages in thread
From: Dmitry Baryshkov @ 2022-08-24 8:25 UTC (permalink / raw)
To: Abhinav Kumar
Cc: freedreno, quic_sbillaka, dianders, airlied, linux-arm-msm,
dri-devel, swboyd, vkoul, agross, bjorn.andersson, quic_aravindh,
Kuogee Hsieh, sean, linux-kernel
On Wed, 24 Aug 2022 at 01:59, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote:
>
>
>
> On 8/23/2022 3:41 PM, Dmitry Baryshkov wrote:
> > On Wed, 24 Aug 2022 at 01:07, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote:
> >> On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
> >>> On 22/08/2022 20:32, Abhinav Kumar wrote:
> >>>>
> >>>>
> >>>> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
> >>>>> On 22/08/2022 19:38, Abhinav Kumar wrote:
> >>>>>> Hi Dmitry
> >>>>>>
> >>>>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
> >>>>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
> >>>>>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
> >>>>>>>> both disable crtc is required and crtc->active is set before pushing
> >>>>>>>> a new frame downstream.
> >>>>>>>>
> >>>>>>>> There is a rare case that user space display manager issue an extra
> >>>>>>>> screen update immediately followed by close DRM device while down
> >>>>>>>> stream display interface is disabled. This extra screen update will
> >>>>>>>> timeout due to the downstream interface is disabled but will cause
> >>>>>>>> crtc->active be set. Hence the followed commit_tails() called by
> >>>>>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
> >>>>>>>> conditions checking even downstream interface is disabled.
> >>>>>>>> This cause the crash to happen at dp_bridge_disable() due to it
> >>>>>>>> trying
> >>>>>>>> to access the main link register to push the idle pattern out
> >>>>>>>> while main
> >>>>>>>> link clocks is disabled.
> >>>>>>>>
> >>>>>>>> This patch adds atomic_check to prevent the extra frame will not
> >>>>>>>> be pushed down if display interface is down so that crtc->active
> >>>>>>>> will not be set neither. This will fail the conditions checking
> >>>>>>>> of disabling down stream crtc/encoder/bridge which prevent
> >>>>>>>> drm_release() from calling dp_bridge_disable() so that crash
> >>>>>>>> at dp_bridge_disable() prevented.
> >>>>>>>
> >>>>>>> I must admit I had troubles parsing this description. However if I
> >>>>>>> got you right, I think the check that the main link clock is
> >>>>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle() would be
> >>>>>>> a better fix.
> >>>>>>
> >>>>>> Originally, thats what was posted
> >>>>>> https://patchwork.freedesktop.org/patch/496984/.
> >>>>>
> >>>>> This patch is also not so correct from my POV. It checks for the hpd
> >>>>> status, while in reality it should check for main link clocks being
> >>>>> enabled.
> >>>>>
> >>>>
> >>>> We can push another fix to check for the clk state instead of the hpd
> >>>> status. But I must say we are again just masking something which the
> >>>> fwk should have avoided isnt it?
> >>>>
> >>>> As per the doc in the include/drm/drm_bridge.h it says,
> >>>>
> >>>> "*
> >>>> * The bridge can assume that the display pipe (i.e. clocks and timing
> >>>> * signals) feeding it is still running when this callback is called.
> >>>> *"
> >>>
> >>> Yes, that's what I meant about this chunk begging to go to the core. In
> >>> my opinion, if we are talking about the disconnected sinks, it is the
> >>> framework who should disallow submitting the frames to the disconnected
> >>> sinks.
> >>>
> >>>>
> >>>> By adding an extra layers of protection in the driver, we are just
> >>>> avoiding another issue but the commit should not have been issued in
> >>>> the first place.
> >>>>
> >>>> So shouldnt we do both then? That is add protection to check if clock
> >>>> is ON and also, reject commits when display is disconnected.
> >>>>
> >>>>>>
> >>>>>> Then it seemed like we were just protecting against an issue in the
> >>>>>> framework which was allowing the frames to be pushed even after the
> >>>>>> display was disconnected. The DP driver did send out the disconnect
> >>>>>> event correctly and as per the logs, this frame came down after that
> >>>>>> and the DRM fwk did allow it.
> >>>>>>
> >>>>>> So after discussing on IRC with Rob, we came up with this approach that
> >>>>>> if the display is not connected, then atomic_check should fail. That
> >>>>>> way the commit will not happen.
> >>>>>>
> >>>>>> Just seemed a bit cleaner instead of adding all our protections.
> >>>>>
> >>>>> The check to fail atomic_check if display is not connected seems out
> >>>>> of place. In its current way it begs go to the upper layer,
> >>>>> forbidding using disconnected sinks for all the drivers. There is
> >>>>> nothing special in the MSM DP driver with respect to the HPD events
> >>>>> processing and failing atomic_check() based on that.
> >>>>>
> >>>>
> >>>> Why all the drivers? This is only for MSM DP bridge.
> >>>
> >>> Yes, we change the MSM DRM driver. But the check is generic enough. I'm
> >>> not actually insisting on pushing the check to the core, just trying to
> >>> understand the real cause here.
> >>>
> >>>>
> >>
> >> I actually wanted to push this to the core and thats what I had
> >> originally asked on IRC because it does seem to be generic enough that
> >> it should belong to the core but after discussion with Rob on freedreno,
> >> he felt this was a better approach because for some of the legacy
> >> connectors like VGA, this need not belong to the DRM core, hence we went
> >> with this approach.
> >
> > It might be better to whitelist such connectors (S-VIDEO/composite
> > comes to my mind rather than VGA).
>
> I am fine with that approach, if Rob is onboard with that.
>
> >
> >>>>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
> >>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
> >>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
> >>>>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> >>>>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
> >>>>>>>> lr : do_raw_spin_lock+0xa4/0xdc
> >>>>>>>> sp : ffffffc01092b6a0
> >>>>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
> >>>>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
> >>>>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
> >>>>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
> >>>>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
> >>>>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
> >>>>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
> >>>>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
> >>>>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
> >>>>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
> >>>>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
> >>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
> >>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
> >>>>>>>> Call trace:
> >>>>>>>> dump_backtrace.part.0+0xbc/0xe4
> >>>>>>>> show_stack+0x24/0x70
> >>>>>>>> dump_stack_lvl+0x68/0x84
> >>>>>>>> dump_stack+0x18/0x34
> >>>>>>>> panic+0x14c/0x32c
> >>>>>>>> nmi_panic+0x58/0x7c
> >>>>>>>> arm64_serror_panic+0x78/0x84
> >>>>>>>> do_serror+0x40/0x64
> >>>>>>>> el1h_64_error_handler+0x30/0x48
> >>>>>>>> el1h_64_error+0x68/0x6c
> >>>>>>>> __cmpxchg_case_acq_32+0x14/0x2c
> >>>>>>>> _raw_spin_lock_irqsave+0x38/0x4c
> >>>
> >>> You know, after re-reading the trace, I could not help but notice that
> >>> the issue seems to be related to completion/timer/spinlock memory
> >>> becoming unavailable rather than disabling the main link clock.
> >>> See, the SError comes in the spin_lock path, not during register read.
> >>>
> >>> Thus I think the commit message is a bit misleading.
> >>>
> >>
> >> No, this issue is due to unclocked access. Please check this part of the
> >> stack:
> >
> > Well, if it were for the unlocked access, we would see SError on the
> > register access, wouldn't we? However in this case the SError comes
> > from the raw spinlock code.
>
> This is not uncommon. With unclocked access, we have seen in the past
> that sometimes the stack is off by one line. The fact that this issue
> got resolved even with the older version of the patch
> https://patchwork.freedesktop.org/patch/496984/ is pointing towards an
> unclocked access and not the dp/dp->ctrl memory pointers.
As far as I understood, the bug is reproducible. Just to make me feel
safe, can we please:
- either have a trace which shows when the clocks are disabled (or not enabled)
- or make sure that keeping the mainlink clock on would also mitigate the issue?
>
> >
> >> >>>>>> wait_for_completion_timeout+0x2c/0x54
> >> >>>>>> dp_ctrl_push_idle+0x40/0x88
> >> >>>>>> dp_bridge_disable+0x24/0x30
> >> >>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
> >> >>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
> >> >>>>>> msm_atomic_commit_tail+0x1d0/0x374
> >> >>>>>> commit_tail+0x80/0x108
> >> >>>>>> drm_atomic_helper_commit+0x118/0x11c
> >> >>>>>> drm_atomic_commit+0xb4/0xe0
> >> >>>>>> drm_client_modeset_commit_atomic+0x184/0x224
> >> >>>>>> drm_client_modeset_commit_locked+0x58/0x160
> >> >>>>>> drm_client_modeset_commit+0x3c/0x64
> >>
> >>> Can we please get a trace checking which calls were actually made for
> >>> the dp bridge and if the dp/dp->ctrl memory pointers are correct?
> >>>
> >>> I do not see the dp_display_disable() being called. Maybe I just missed
> >>> the call.
> >>>
> >>
> >> Yes it is called, please refer to the above part of the stack that I
> >> have pasted.
> >
> > The stacktrace mentions dp_bridge_disable(), not dp_display_disable()
> > (which I asked for).
> >
>
> So whats happening here is the crash is happening in dp_bridge_disable().
>
> dp_display_disable() is called from post_disable() thats why it doesnt
> show up in the stack.
>
Yes. But the mainlink clocks are disabled in dp_display_disable()
that's why I'm asking if the function was called at all.
--
With best wishes
Dmitry
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-24 8:25 ` Dmitry Baryshkov
@ 2022-08-24 19:16 ` Abhinav Kumar
2022-08-26 8:19 ` Dmitry Baryshkov
0 siblings, 1 reply; 14+ messages in thread
From: Abhinav Kumar @ 2022-08-24 19:16 UTC (permalink / raw)
To: Dmitry Baryshkov
Cc: freedreno, quic_sbillaka, dianders, airlied, linux-arm-msm,
dri-devel, swboyd, vkoul, agross, bjorn.andersson, quic_aravindh,
Kuogee Hsieh, sean, linux-kernel
On 8/24/2022 1:25 AM, Dmitry Baryshkov wrote:
> On Wed, 24 Aug 2022 at 01:59, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote:
>>
>>
>>
>> On 8/23/2022 3:41 PM, Dmitry Baryshkov wrote:
>>> On Wed, 24 Aug 2022 at 01:07, Abhinav Kumar <quic_abhinavk@quicinc.com> wrote:
>>>> On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
>>>>> On 22/08/2022 20:32, Abhinav Kumar wrote:
>>>>>>
>>>>>>
>>>>>> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
>>>>>>> On 22/08/2022 19:38, Abhinav Kumar wrote:
>>>>>>>> Hi Dmitry
>>>>>>>>
>>>>>>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>>>>>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>>>>>>>> DRM commit_tails() will disable downstream crtc/encoder/bridge if
>>>>>>>>>> both disable crtc is required and crtc->active is set before pushing
>>>>>>>>>> a new frame downstream.
>>>>>>>>>>
>>>>>>>>>> There is a rare case that user space display manager issue an extra
>>>>>>>>>> screen update immediately followed by close DRM device while down
>>>>>>>>>> stream display interface is disabled. This extra screen update will
>>>>>>>>>> timeout due to the downstream interface is disabled but will cause
>>>>>>>>>> crtc->active be set. Hence the followed commit_tails() called by
>>>>>>>>>> drm_release() will pass the disable downstream crtc/encoder/bridge
>>>>>>>>>> conditions checking even downstream interface is disabled.
>>>>>>>>>> This cause the crash to happen at dp_bridge_disable() due to it
>>>>>>>>>> trying
>>>>>>>>>> to access the main link register to push the idle pattern out
>>>>>>>>>> while main
>>>>>>>>>> link clocks is disabled.
>>>>>>>>>>
>>>>>>>>>> This patch adds atomic_check to prevent the extra frame will not
>>>>>>>>>> be pushed down if display interface is down so that crtc->active
>>>>>>>>>> will not be set neither. This will fail the conditions checking
>>>>>>>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>>>>>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>>>>>>>> at dp_bridge_disable() prevented.
>>>>>>>>>
>>>>>>>>> I must admit I had troubles parsing this description. However if I
>>>>>>>>> got you right, I think the check that the main link clock is
>>>>>>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle() would be
>>>>>>>>> a better fix.
>>>>>>>>
>>>>>>>> Originally, thats what was posted
>>>>>>>> https://patchwork.freedesktop.org/patch/496984/.
>>>>>>>
>>>>>>> This patch is also not so correct from my POV. It checks for the hpd
>>>>>>> status, while in reality it should check for main link clocks being
>>>>>>> enabled.
>>>>>>>
>>>>>>
>>>>>> We can push another fix to check for the clk state instead of the hpd
>>>>>> status. But I must say we are again just masking something which the
>>>>>> fwk should have avoided isnt it?
>>>>>>
>>>>>> As per the doc in the include/drm/drm_bridge.h it says,
>>>>>>
>>>>>> "*
>>>>>> * The bridge can assume that the display pipe (i.e. clocks and timing
>>>>>> * signals) feeding it is still running when this callback is called.
>>>>>> *"
>>>>>
>>>>> Yes, that's what I meant about this chunk begging to go to the core. In
>>>>> my opinion, if we are talking about the disconnected sinks, it is the
>>>>> framework who should disallow submitting the frames to the disconnected
>>>>> sinks.
>>>>>
>>>>>>
>>>>>> By adding an extra layers of protection in the driver, we are just
>>>>>> avoiding another issue but the commit should not have been issued in
>>>>>> the first place.
>>>>>>
>>>>>> So shouldnt we do both then? That is add protection to check if clock
>>>>>> is ON and also, reject commits when display is disconnected.
>>>>>>
>>>>>>>>
>>>>>>>> Then it seemed like we were just protecting against an issue in the
>>>>>>>> framework which was allowing the frames to be pushed even after the
>>>>>>>> display was disconnected. The DP driver did send out the disconnect
>>>>>>>> event correctly and as per the logs, this frame came down after that
>>>>>>>> and the DRM fwk did allow it.
>>>>>>>>
>>>>>>>> So after discussing on IRC with Rob, we came up with this approach that
>>>>>>>> if the display is not connected, then atomic_check should fail. That
>>>>>>>> way the commit will not happen.
>>>>>>>>
>>>>>>>> Just seemed a bit cleaner instead of adding all our protections.
>>>>>>>
>>>>>>> The check to fail atomic_check if display is not connected seems out
>>>>>>> of place. In its current way it begs go to the upper layer,
>>>>>>> forbidding using disconnected sinks for all the drivers. There is
>>>>>>> nothing special in the MSM DP driver with respect to the HPD events
>>>>>>> processing and failing atomic_check() based on that.
>>>>>>>
>>>>>>
>>>>>> Why all the drivers? This is only for MSM DP bridge.
>>>>>
>>>>> Yes, we change the MSM DRM driver. But the check is generic enough. I'm
>>>>> not actually insisting on pushing the check to the core, just trying to
>>>>> understand the real cause here.
>>>>>
>>>>>>
>>>>
>>>> I actually wanted to push this to the core and thats what I had
>>>> originally asked on IRC because it does seem to be generic enough that
>>>> it should belong to the core but after discussion with Rob on freedreno,
>>>> he felt this was a better approach because for some of the legacy
>>>> connectors like VGA, this need not belong to the DRM core, hence we went
>>>> with this approach.
>>>
>>> It might be better to whitelist such connectors (S-VIDEO/composite
>>> comes to my mind rather than VGA).
>>
>> I am fine with that approach, if Rob is onboard with that.
>>
>>>
>>>>>>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>>>>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>>>>>>>> sp : ffffffc01092b6a0
>>>>>>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27: 0000000000000038
>>>>>>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24: 0000000000000000
>>>>>>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21: ffffffd2978d0008
>>>>>>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18: 0000000000000000
>>>>>>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15: 04380000089807d0
>>>>>>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12: 0000000000000000
>>>>>>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 : ffffffd2973e09e4
>>>>>>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 : 0000000000000001
>>>>>>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 : ffffff80ff759fc0
>>>>>>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 : ffffff80ff759fc0
>>>>>>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>>>> Call trace:
>>>>>>>>>> dump_backtrace.part.0+0xbc/0xe4
>>>>>>>>>> show_stack+0x24/0x70
>>>>>>>>>> dump_stack_lvl+0x68/0x84
>>>>>>>>>> dump_stack+0x18/0x34
>>>>>>>>>> panic+0x14c/0x32c
>>>>>>>>>> nmi_panic+0x58/0x7c
>>>>>>>>>> arm64_serror_panic+0x78/0x84
>>>>>>>>>> do_serror+0x40/0x64
>>>>>>>>>> el1h_64_error_handler+0x30/0x48
>>>>>>>>>> el1h_64_error+0x68/0x6c
>>>>>>>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>>>> _raw_spin_lock_irqsave+0x38/0x4c
>>>>>
>>>>> You know, after re-reading the trace, I could not help but notice that
>>>>> the issue seems to be related to completion/timer/spinlock memory
>>>>> becoming unavailable rather than disabling the main link clock.
>>>>> See, the SError comes in the spin_lock path, not during register read.
>>>>>
>>>>> Thus I think the commit message is a bit misleading.
>>>>>
>>>>
>>>> No, this issue is due to unclocked access. Please check this part of the
>>>> stack:
>>>
>>> Well, if it were for the unlocked access, we would see SError on the
>>> register access, wouldn't we? However in this case the SError comes
>>> from the raw spinlock code.
>>
>> This is not uncommon. With unclocked access, we have seen in the past
>> that sometimes the stack is off by one line. The fact that this issue
>> got resolved even with the older version of the patch
>> https://patchwork.freedesktop.org/patch/496984/ is pointing towards an
>> unclocked access and not the dp/dp->ctrl memory pointers.
>
> As far as I understood, the bug is reproducible. Just to make me feel
> safe, can we please:
> - either have a trace which shows when the clocks are disabled (or not enabled)
> - or make sure that keeping the mainlink clock on would also mitigate the issue?
Yes, this trace is already available with all the drm_dbg_dp messages
enabled. Please refer to the attachment named
2022-08-15-dmesg-drm-4K-crash.txt in the bug
https://gitlab.freedesktop.org/drm/msm/-/issues/17.
You can jump to this section of the log.
[ 99.191216] msm_dpu ae01000.mdp: [drm:dp_display_host_phy_exit]
type=10 core_init=1 phy_init=1
[ 99.192354] [drm:dp_ctrl_phy_exit] phy=00000000b9b91350 init=0 power_on=0
[ 99.192369] msm_dpu ae01000.mdp:
[drm:dp_display_disable.constprop.0.isra.0] sink count: 1
Here is the dp_display_disable() you were looking for.
[ 99.192378] msm_dpu ae01000.mdp: [drm:dp_bridge_post_disable] type=10
Done
[ 99.192389] msm_dpu ae01000.mdp:
[drm:drm_atomic_helper_commit_modeset_disables] disabling [CRTC:60:crtc-1]
[ 99.192561] [drm:dpu_crtc_disable] no frames pending
[ 99.192571] [drm:dpu_core_perf_crtc_update] crtc:60 stop_req:1
core_clk:200000000
[ 99.192581] [drm:dpu_core_perf_crtc_update] crtc=60 disable
[ 99.192588] [drm:_dpu_core_perf_crtc_update_bus] crtc=59 bw=0 paths:1
[ 99.192595] [drm:_dpu_core_perf_crtc_update_bus] crtc=60 bw=0 paths:1
[ 99.192700] [drm:dpu_core_perf_crtc_update] clk:200000000
[ 99.192714] [drm:dpu_core_perf_crtc_update] update clk rate =
200000000 HZ
[ 99.192729] msm_dpu ae01000.mdp:
[drm:drm_atomic_helper_commit_modeset_disables] modeset on
[ENCODER:33:TMDS-33]
[ 99.192738] [drm:dpu_encoder_virt_atomic_mode_set] enc33
[ 99.192749] [drm:dpu_crtc_atomic_begin] crtc59
>
>>
>>>
>>>> >>>>>> wait_for_completion_timeout+0x2c/0x54
>>>> >>>>>> dp_ctrl_push_idle+0x40/0x88
>>>> >>>>>> dp_bridge_disable+0x24/0x30
>>>> >>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>> >>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>> >>>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>> >>>>>> commit_tail+0x80/0x108
>>>> >>>>>> drm_atomic_helper_commit+0x118/0x11c
>>>> >>>>>> drm_atomic_commit+0xb4/0xe0
>>>> >>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>> >>>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>> >>>>>> drm_client_modeset_commit+0x3c/0x64
>>>>
>>>>> Can we please get a trace checking which calls were actually made for
>>>>> the dp bridge and if the dp/dp->ctrl memory pointers are correct?
>>>>>
>>>>> I do not see the dp_display_disable() being called. Maybe I just missed
>>>>> the call.
>>>>>
>>>>
>>>> Yes it is called, please refer to the above part of the stack that I
>>>> have pasted.
>>>
>>> The stacktrace mentions dp_bridge_disable(), not dp_display_disable()
>>> (which I asked for).
>>>
>>
>> So whats happening here is the crash is happening in dp_bridge_disable().
>>
>> dp_display_disable() is called from post_disable() thats why it doesnt
>> show up in the stack.
>>
>
> Yes. But the mainlink clocks are disabled in dp_display_disable()
> that's why I'm asking if the function was called at all.
Now, I see why you were asking about dp_display_disable(). So basically
your question is that when did dp_display_disable() happen that disabled
the clocks causing this issue.
dp_display_disable() happened when the cable was disconnected as shown
in the above section of the logs.
We also sent the disconnected uevent to the usermode. But this commit is
happening from the drm_lastclose() context which doesnt check the
connection status.
This leads to a commit after the cable has been disconnected causing the
unclocked access.
You can refer this log and comment if something is still not clear to you.
>
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-24 19:16 ` Abhinav Kumar
@ 2022-08-26 8:19 ` Dmitry Baryshkov
2022-08-26 16:39 ` Abhinav Kumar
0 siblings, 1 reply; 14+ messages in thread
From: Dmitry Baryshkov @ 2022-08-26 8:19 UTC (permalink / raw)
To: Abhinav Kumar
Cc: freedreno, quic_sbillaka, dianders, airlied, linux-arm-msm,
dri-devel, swboyd, vkoul, agross, bjorn.andersson, quic_aravindh,
Kuogee Hsieh, sean, linux-kernel
On 24/08/2022 22:16, Abhinav Kumar wrote:
>
>
> On 8/24/2022 1:25 AM, Dmitry Baryshkov wrote:
>> On Wed, 24 Aug 2022 at 01:59, Abhinav Kumar
>> <quic_abhinavk@quicinc.com> wrote:
>>>
>>>
>>>
>>> On 8/23/2022 3:41 PM, Dmitry Baryshkov wrote:
>>>> On Wed, 24 Aug 2022 at 01:07, Abhinav Kumar
>>>> <quic_abhinavk@quicinc.com> wrote:
>>>>> On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
>>>>>> On 22/08/2022 20:32, Abhinav Kumar wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
>>>>>>>> On 22/08/2022 19:38, Abhinav Kumar wrote:
>>>>>>>>> Hi Dmitry
>>>>>>>>>
>>>>>>>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>>>>>>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>>>>>>>>> DRM commit_tails() will disable downstream
>>>>>>>>>>> crtc/encoder/bridge if
>>>>>>>>>>> both disable crtc is required and crtc->active is set before
>>>>>>>>>>> pushing
>>>>>>>>>>> a new frame downstream.
>>>>>>>>>>>
>>>>>>>>>>> There is a rare case that user space display manager issue an
>>>>>>>>>>> extra
>>>>>>>>>>> screen update immediately followed by close DRM device while
>>>>>>>>>>> down
>>>>>>>>>>> stream display interface is disabled. This extra screen
>>>>>>>>>>> update will
>>>>>>>>>>> timeout due to the downstream interface is disabled but will
>>>>>>>>>>> cause
>>>>>>>>>>> crtc->active be set. Hence the followed commit_tails() called by
>>>>>>>>>>> drm_release() will pass the disable downstream
>>>>>>>>>>> crtc/encoder/bridge
>>>>>>>>>>> conditions checking even downstream interface is disabled.
>>>>>>>>>>> This cause the crash to happen at dp_bridge_disable() due to it
>>>>>>>>>>> trying
>>>>>>>>>>> to access the main link register to push the idle pattern out
>>>>>>>>>>> while main
>>>>>>>>>>> link clocks is disabled.
>>>>>>>>>>>
>>>>>>>>>>> This patch adds atomic_check to prevent the extra frame will not
>>>>>>>>>>> be pushed down if display interface is down so that crtc->active
>>>>>>>>>>> will not be set neither. This will fail the conditions checking
>>>>>>>>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>>>>>>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>>>>>>>>> at dp_bridge_disable() prevented.
>>>>>>>>>>
>>>>>>>>>> I must admit I had troubles parsing this description. However
>>>>>>>>>> if I
>>>>>>>>>> got you right, I think the check that the main link clock is
>>>>>>>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle()
>>>>>>>>>> would be
>>>>>>>>>> a better fix.
>>>>>>>>>
>>>>>>>>> Originally, thats what was posted
>>>>>>>>> https://patchwork.freedesktop.org/patch/496984/.
>>>>>>>>
>>>>>>>> This patch is also not so correct from my POV. It checks for the
>>>>>>>> hpd
>>>>>>>> status, while in reality it should check for main link clocks being
>>>>>>>> enabled.
>>>>>>>>
>>>>>>>
>>>>>>> We can push another fix to check for the clk state instead of the
>>>>>>> hpd
>>>>>>> status. But I must say we are again just masking something which the
>>>>>>> fwk should have avoided isnt it?
>>>>>>>
>>>>>>> As per the doc in the include/drm/drm_bridge.h it says,
>>>>>>>
>>>>>>> "*
>>>>>>> * The bridge can assume that the display pipe (i.e. clocks
>>>>>>> and timing
>>>>>>> * signals) feeding it is still running when this callback is
>>>>>>> called.
>>>>>>> *"
>>>>>>
>>>>>> Yes, that's what I meant about this chunk begging to go to the
>>>>>> core. In
>>>>>> my opinion, if we are talking about the disconnected sinks, it is the
>>>>>> framework who should disallow submitting the frames to the
>>>>>> disconnected
>>>>>> sinks.
>>>>>>
>>>>>>>
>>>>>>> By adding an extra layers of protection in the driver, we are just
>>>>>>> avoiding another issue but the commit should not have been issued in
>>>>>>> the first place.
>>>>>>>
>>>>>>> So shouldnt we do both then? That is add protection to check if
>>>>>>> clock
>>>>>>> is ON and also, reject commits when display is disconnected.
>>>>>>>
>>>>>>>>>
>>>>>>>>> Then it seemed like we were just protecting against an issue in
>>>>>>>>> the
>>>>>>>>> framework which was allowing the frames to be pushed even after
>>>>>>>>> the
>>>>>>>>> display was disconnected. The DP driver did send out the
>>>>>>>>> disconnect
>>>>>>>>> event correctly and as per the logs, this frame came down after
>>>>>>>>> that
>>>>>>>>> and the DRM fwk did allow it.
>>>>>>>>>
>>>>>>>>> So after discussing on IRC with Rob, we came up with this
>>>>>>>>> approach that
>>>>>>>>> if the display is not connected, then atomic_check should fail.
>>>>>>>>> That
>>>>>>>>> way the commit will not happen.
>>>>>>>>>
>>>>>>>>> Just seemed a bit cleaner instead of adding all our protections.
>>>>>>>>
>>>>>>>> The check to fail atomic_check if display is not connected seems
>>>>>>>> out
>>>>>>>> of place. In its current way it begs go to the upper layer,
>>>>>>>> forbidding using disconnected sinks for all the drivers. There is
>>>>>>>> nothing special in the MSM DP driver with respect to the HPD events
>>>>>>>> processing and failing atomic_check() based on that.
>>>>>>>>
>>>>>>>
>>>>>>> Why all the drivers? This is only for MSM DP bridge.
>>>>>>
>>>>>> Yes, we change the MSM DRM driver. But the check is generic
>>>>>> enough. I'm
>>>>>> not actually insisting on pushing the check to the core, just
>>>>>> trying to
>>>>>> understand the real cause here.
>>>>>>
>>>>>>>
>>>>>
>>>>> I actually wanted to push this to the core and thats what I had
>>>>> originally asked on IRC because it does seem to be generic enough that
>>>>> it should belong to the core but after discussion with Rob on
>>>>> freedreno,
>>>>> he felt this was a better approach because for some of the legacy
>>>>> connectors like VGA, this need not belong to the DRM core, hence we
>>>>> went
>>>>> with this approach.
>>>>
>>>> It might be better to whitelist such connectors (S-VIDEO/composite
>>>> comes to my mind rather than VGA).
>>>
>>> I am fine with that approach, if Rob is onboard with that.
>>>
>>>>
>>>>>>>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>>>>>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>>>>>>>>> sp : ffffffc01092b6a0
>>>>>>>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27:
>>>>>>>>>>> 0000000000000038
>>>>>>>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24:
>>>>>>>>>>> 0000000000000000
>>>>>>>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21:
>>>>>>>>>>> ffffffd2978d0008
>>>>>>>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18:
>>>>>>>>>>> 0000000000000000
>>>>>>>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15:
>>>>>>>>>>> 04380000089807d0
>>>>>>>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12:
>>>>>>>>>>> 0000000000000000
>>>>>>>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 :
>>>>>>>>>>> ffffffd2973e09e4
>>>>>>>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 :
>>>>>>>>>>> 0000000000000001
>>>>>>>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 :
>>>>>>>>>>> ffffff80ff759fc0
>>>>>>>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 :
>>>>>>>>>>> ffffff80ff759fc0
>>>>>>>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>>>>> Call trace:
>>>>>>>>>>> dump_backtrace.part.0+0xbc/0xe4
>>>>>>>>>>> show_stack+0x24/0x70
>>>>>>>>>>> dump_stack_lvl+0x68/0x84
>>>>>>>>>>> dump_stack+0x18/0x34
>>>>>>>>>>> panic+0x14c/0x32c
>>>>>>>>>>> nmi_panic+0x58/0x7c
>>>>>>>>>>> arm64_serror_panic+0x78/0x84
>>>>>>>>>>> do_serror+0x40/0x64
>>>>>>>>>>> el1h_64_error_handler+0x30/0x48
>>>>>>>>>>> el1h_64_error+0x68/0x6c
>>>>>>>>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>>>>> _raw_spin_lock_irqsave+0x38/0x4c
>>>>>>
>>>>>> You know, after re-reading the trace, I could not help but notice
>>>>>> that
>>>>>> the issue seems to be related to completion/timer/spinlock memory
>>>>>> becoming unavailable rather than disabling the main link clock.
>>>>>> See, the SError comes in the spin_lock path, not during register
>>>>>> read.
>>>>>>
>>>>>> Thus I think the commit message is a bit misleading.
>>>>>>
>>>>>
>>>>> No, this issue is due to unclocked access. Please check this part
>>>>> of the
>>>>> stack:
>>>>
>>>> Well, if it were for the unlocked access, we would see SError on the
>>>> register access, wouldn't we? However in this case the SError comes
>>>> from the raw spinlock code.
>>>
>>> This is not uncommon. With unclocked access, we have seen in the past
>>> that sometimes the stack is off by one line. The fact that this issue
>>> got resolved even with the older version of the patch
>>> https://patchwork.freedesktop.org/patch/496984/ is pointing towards an
>>> unclocked access and not the dp/dp->ctrl memory pointers.
>>
>> As far as I understood, the bug is reproducible. Just to make me feel
>> safe, can we please:
>> - either have a trace which shows when the clocks are disabled (or
>> not enabled)
>> - or make sure that keeping the mainlink clock on would also mitigate
>> the issue?
>
> Yes, this trace is already available with all the drm_dbg_dp messages
> enabled. Please refer to the attachment named
> 2022-08-15-dmesg-drm-4K-crash.txt in the bug
> https://gitlab.freedesktop.org/drm/msm/-/issues/17.
>
> You can jump to this section of the log.
>
> [ 99.191216] msm_dpu ae01000.mdp: [drm:dp_display_host_phy_exit]
> type=10 core_init=1 phy_init=1
> [ 99.192354] [drm:dp_ctrl_phy_exit] phy=00000000b9b91350 init=0
> power_on=0
> [ 99.192369] msm_dpu ae01000.mdp:
> [drm:dp_display_disable.constprop.0.isra.0] sink count: 1
>
> Here is the dp_display_disable() you were looking for.
>
> [ 99.192378] msm_dpu ae01000.mdp: [drm:dp_bridge_post_disable] type=10
> Done
> [ 99.192389] msm_dpu ae01000.mdp:
> [drm:drm_atomic_helper_commit_modeset_disables] disabling [CRTC:60:crtc-1]
> [ 99.192561] [drm:dpu_crtc_disable] no frames pending
> [ 99.192571] [drm:dpu_core_perf_crtc_update] crtc:60 stop_req:1
> core_clk:200000000
> [ 99.192581] [drm:dpu_core_perf_crtc_update] crtc=60 disable
> [ 99.192588] [drm:_dpu_core_perf_crtc_update_bus] crtc=59 bw=0 paths:1
> [ 99.192595] [drm:_dpu_core_perf_crtc_update_bus] crtc=60 bw=0 paths:1
> [ 99.192700] [drm:dpu_core_perf_crtc_update] clk:200000000
> [ 99.192714] [drm:dpu_core_perf_crtc_update] update clk rate =
> 200000000 HZ
> [ 99.192729] msm_dpu ae01000.mdp:
> [drm:drm_atomic_helper_commit_modeset_disables] modeset on
> [ENCODER:33:TMDS-33]
> [ 99.192738] [drm:dpu_encoder_virt_atomic_mode_set] enc33
> [ 99.192749] [drm:dpu_crtc_atomic_begin] crtc59
>>
>>>
>>>>
>>>>> >>>>>> wait_for_completion_timeout+0x2c/0x54
>>>>> >>>>>> dp_ctrl_push_idle+0x40/0x88
>>>>> >>>>>> dp_bridge_disable+0x24/0x30
>>>>> >>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>>> >>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>>> >>>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>>> >>>>>> commit_tail+0x80/0x108
>>>>> >>>>>> drm_atomic_helper_commit+0x118/0x11c
>>>>> >>>>>> drm_atomic_commit+0xb4/0xe0
>>>>> >>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>>> >>>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>>> >>>>>> drm_client_modeset_commit+0x3c/0x64
>>>>>
>>>>>> Can we please get a trace checking which calls were actually made for
>>>>>> the dp bridge and if the dp/dp->ctrl memory pointers are correct?
>>>>>>
>>>>>> I do not see the dp_display_disable() being called. Maybe I just
>>>>>> missed
>>>>>> the call.
>>>>>>
>>>>>
>>>>> Yes it is called, please refer to the above part of the stack that I
>>>>> have pasted.
>>>>
>>>> The stacktrace mentions dp_bridge_disable(), not dp_display_disable()
>>>> (which I asked for).
>>>>
>>>
>>> So whats happening here is the crash is happening in
>>> dp_bridge_disable().
>>>
>>> dp_display_disable() is called from post_disable() thats why it doesnt
>>> show up in the stack.
>>>
>>
>> Yes. But the mainlink clocks are disabled in dp_display_disable()
>> that's why I'm asking if the function was called at all.
>
> Now, I see why you were asking about dp_display_disable(). So basically
> your question is that when did dp_display_disable() happen that disabled
> the clocks causing this issue.
>
> dp_display_disable() happened when the cable was disconnected as shown
> in the above section of the logs.
>
> We also sent the disconnected uevent to the usermode. But this commit is
> happening from the drm_lastclose() context which doesnt check the
> connection status.
>
> This leads to a commit after the cable has been disconnected causing the
> unclocked access.
>
> You can refer this log and comment if something is still not clear to you.
I have spent some time comparing the log and the programming logic.
I found what I was looking for: a safeguard for not doing the disable
twice. The disable_outputs() function, the one which calls
drm_atomic_bridge_chain_disable() has a logical check which should have
acted as a safety net here: it checks whether crtc_needs_disable().
Can you please doublecheck why doesn't it reflect the fact that CRTC
doesn't need disabling as it has been already disabled. If I understand
correctly this boils down to CRTC's old_state->active being set, while
the CRTC has been effectively disabled.
--
With best wishes
Dmitry
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] drm/msm/dp: add atomic_check to bridge ops
2022-08-26 8:19 ` Dmitry Baryshkov
@ 2022-08-26 16:39 ` Abhinav Kumar
0 siblings, 0 replies; 14+ messages in thread
From: Abhinav Kumar @ 2022-08-26 16:39 UTC (permalink / raw)
To: Dmitry Baryshkov
Cc: freedreno, quic_sbillaka, dianders, airlied, linux-arm-msm,
dri-devel, swboyd, vkoul, agross, bjorn.andersson, quic_aravindh,
Kuogee Hsieh, sean, linux-kernel
On 8/26/2022 1:19 AM, Dmitry Baryshkov wrote:
> On 24/08/2022 22:16, Abhinav Kumar wrote:
>>
>>
>> On 8/24/2022 1:25 AM, Dmitry Baryshkov wrote:
>>> On Wed, 24 Aug 2022 at 01:59, Abhinav Kumar
>>> <quic_abhinavk@quicinc.com> wrote:
>>>>
>>>>
>>>>
>>>> On 8/23/2022 3:41 PM, Dmitry Baryshkov wrote:
>>>>> On Wed, 24 Aug 2022 at 01:07, Abhinav Kumar
>>>>> <quic_abhinavk@quicinc.com> wrote:
>>>>>> On 8/22/2022 11:33 AM, Dmitry Baryshkov wrote:
>>>>>>> On 22/08/2022 20:32, Abhinav Kumar wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> On 8/22/2022 9:49 AM, Dmitry Baryshkov wrote:
>>>>>>>>> On 22/08/2022 19:38, Abhinav Kumar wrote:
>>>>>>>>>> Hi Dmitry
>>>>>>>>>>
>>>>>>>>>> On 8/22/2022 9:18 AM, Dmitry Baryshkov wrote:
>>>>>>>>>>> On 17/08/2022 21:01, Kuogee Hsieh wrote:
>>>>>>>>>>>> DRM commit_tails() will disable downstream
>>>>>>>>>>>> crtc/encoder/bridge if
>>>>>>>>>>>> both disable crtc is required and crtc->active is set before
>>>>>>>>>>>> pushing
>>>>>>>>>>>> a new frame downstream.
>>>>>>>>>>>>
>>>>>>>>>>>> There is a rare case that user space display manager issue
>>>>>>>>>>>> an extra
>>>>>>>>>>>> screen update immediately followed by close DRM device while
>>>>>>>>>>>> down
>>>>>>>>>>>> stream display interface is disabled. This extra screen
>>>>>>>>>>>> update will
>>>>>>>>>>>> timeout due to the downstream interface is disabled but will
>>>>>>>>>>>> cause
>>>>>>>>>>>> crtc->active be set. Hence the followed commit_tails()
>>>>>>>>>>>> called by
>>>>>>>>>>>> drm_release() will pass the disable downstream
>>>>>>>>>>>> crtc/encoder/bridge
>>>>>>>>>>>> conditions checking even downstream interface is disabled.
>>>>>>>>>>>> This cause the crash to happen at dp_bridge_disable() due to it
>>>>>>>>>>>> trying
>>>>>>>>>>>> to access the main link register to push the idle pattern out
>>>>>>>>>>>> while main
>>>>>>>>>>>> link clocks is disabled.
>>>>>>>>>>>>
>>>>>>>>>>>> This patch adds atomic_check to prevent the extra frame will
>>>>>>>>>>>> not
>>>>>>>>>>>> be pushed down if display interface is down so that
>>>>>>>>>>>> crtc->active
>>>>>>>>>>>> will not be set neither. This will fail the conditions checking
>>>>>>>>>>>> of disabling down stream crtc/encoder/bridge which prevent
>>>>>>>>>>>> drm_release() from calling dp_bridge_disable() so that crash
>>>>>>>>>>>> at dp_bridge_disable() prevented.
>>>>>>>>>>>
>>>>>>>>>>> I must admit I had troubles parsing this description. However
>>>>>>>>>>> if I
>>>>>>>>>>> got you right, I think the check that the main link clock is
>>>>>>>>>>> running in the dp_bridge_disable() or dp_ctrl_push_idle()
>>>>>>>>>>> would be
>>>>>>>>>>> a better fix.
>>>>>>>>>>
>>>>>>>>>> Originally, thats what was posted
>>>>>>>>>> https://patchwork.freedesktop.org/patch/496984/.
>>>>>>>>>
>>>>>>>>> This patch is also not so correct from my POV. It checks for
>>>>>>>>> the hpd
>>>>>>>>> status, while in reality it should check for main link clocks
>>>>>>>>> being
>>>>>>>>> enabled.
>>>>>>>>>
>>>>>>>>
>>>>>>>> We can push another fix to check for the clk state instead of
>>>>>>>> the hpd
>>>>>>>> status. But I must say we are again just masking something which
>>>>>>>> the
>>>>>>>> fwk should have avoided isnt it?
>>>>>>>>
>>>>>>>> As per the doc in the include/drm/drm_bridge.h it says,
>>>>>>>>
>>>>>>>> "*
>>>>>>>> * The bridge can assume that the display pipe (i.e. clocks
>>>>>>>> and timing
>>>>>>>> * signals) feeding it is still running when this callback is
>>>>>>>> called.
>>>>>>>> *"
>>>>>>>
>>>>>>> Yes, that's what I meant about this chunk begging to go to the
>>>>>>> core. In
>>>>>>> my opinion, if we are talking about the disconnected sinks, it is
>>>>>>> the
>>>>>>> framework who should disallow submitting the frames to the
>>>>>>> disconnected
>>>>>>> sinks.
>>>>>>>
>>>>>>>>
>>>>>>>> By adding an extra layers of protection in the driver, we are just
>>>>>>>> avoiding another issue but the commit should not have been
>>>>>>>> issued in
>>>>>>>> the first place.
>>>>>>>>
>>>>>>>> So shouldnt we do both then? That is add protection to check if
>>>>>>>> clock
>>>>>>>> is ON and also, reject commits when display is disconnected.
>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Then it seemed like we were just protecting against an issue
>>>>>>>>>> in the
>>>>>>>>>> framework which was allowing the frames to be pushed even
>>>>>>>>>> after the
>>>>>>>>>> display was disconnected. The DP driver did send out the
>>>>>>>>>> disconnect
>>>>>>>>>> event correctly and as per the logs, this frame came down
>>>>>>>>>> after that
>>>>>>>>>> and the DRM fwk did allow it.
>>>>>>>>>>
>>>>>>>>>> So after discussing on IRC with Rob, we came up with this
>>>>>>>>>> approach that
>>>>>>>>>> if the display is not connected, then atomic_check should
>>>>>>>>>> fail. That
>>>>>>>>>> way the commit will not happen.
>>>>>>>>>>
>>>>>>>>>> Just seemed a bit cleaner instead of adding all our protections.
>>>>>>>>>
>>>>>>>>> The check to fail atomic_check if display is not connected
>>>>>>>>> seems out
>>>>>>>>> of place. In its current way it begs go to the upper layer,
>>>>>>>>> forbidding using disconnected sinks for all the drivers. There is
>>>>>>>>> nothing special in the MSM DP driver with respect to the HPD
>>>>>>>>> events
>>>>>>>>> processing and failing atomic_check() based on that.
>>>>>>>>>
>>>>>>>>
>>>>>>>> Why all the drivers? This is only for MSM DP bridge.
>>>>>>>
>>>>>>> Yes, we change the MSM DRM driver. But the check is generic
>>>>>>> enough. I'm
>>>>>>> not actually insisting on pushing the check to the core, just
>>>>>>> trying to
>>>>>>> understand the real cause here.
>>>>>>>
>>>>>>>>
>>>>>>
>>>>>> I actually wanted to push this to the core and thats what I had
>>>>>> originally asked on IRC because it does seem to be generic enough
>>>>>> that
>>>>>> it should belong to the core but after discussion with Rob on
>>>>>> freedreno,
>>>>>> he felt this was a better approach because for some of the legacy
>>>>>> connectors like VGA, this need not belong to the DRM core, hence
>>>>>> we went
>>>>>> with this approach.
>>>>>
>>>>> It might be better to whitelist such connectors (S-VIDEO/composite
>>>>> comes to my mind rather than VGA).
>>>>
>>>> I am fine with that approach, if Rob is onboard with that.
>>>>
>>>>>
>>>>>>>>>>>> SError Interrupt on CPU7, code 0x00000000be000411 -- SError
>>>>>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>>>>>> pstate: a04000c9 (NzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>>>>>>>>>> pc : __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>>>>>> lr : do_raw_spin_lock+0xa4/0xdc
>>>>>>>>>>>> sp : ffffffc01092b6a0
>>>>>>>>>>>> x29: ffffffc01092b6a0 x28: 0000000000000028 x27:
>>>>>>>>>>>> 0000000000000038
>>>>>>>>>>>> x26: 0000000000000004 x25: ffffffd2973dce48 x24:
>>>>>>>>>>>> 0000000000000000
>>>>>>>>>>>> x23: 00000000ffffffff x22: 00000000ffffffff x21:
>>>>>>>>>>>> ffffffd2978d0008
>>>>>>>>>>>> x20: ffffffd2978d0008 x19: ffffff80ff759fc0 x18:
>>>>>>>>>>>> 0000000000000000
>>>>>>>>>>>> x17: 004800a501260460 x16: 0441043b04600438 x15:
>>>>>>>>>>>> 04380000089807d0
>>>>>>>>>>>> x14: 07b0089807800780 x13: 0000000000000000 x12:
>>>>>>>>>>>> 0000000000000000
>>>>>>>>>>>> x11: 0000000000000438 x10: 00000000000007d0 x9 :
>>>>>>>>>>>> ffffffd2973e09e4
>>>>>>>>>>>> x8 : ffffff8092d53300 x7 : ffffff808902e8b8 x6 :
>>>>>>>>>>>> 0000000000000001
>>>>>>>>>>>> x5 : ffffff808902e880 x4 : 0000000000000000 x3 :
>>>>>>>>>>>> ffffff80ff759fc0
>>>>>>>>>>>> x2 : 0000000000000001 x1 : 0000000000000000 x0 :
>>>>>>>>>>>> ffffff80ff759fc0
>>>>>>>>>>>> Kernel panic - not syncing: Asynchronous SError Interrupt
>>>>>>>>>>>> CPU: 7 PID: 3878 Comm: Xorg Not tainted 5.19.0-stb-cbq #19
>>>>>>>>>>>> Hardware name: Google Lazor (rev3 - 8) (DT)
>>>>>>>>>>>> Call trace:
>>>>>>>>>>>> dump_backtrace.part.0+0xbc/0xe4
>>>>>>>>>>>> show_stack+0x24/0x70
>>>>>>>>>>>> dump_stack_lvl+0x68/0x84
>>>>>>>>>>>> dump_stack+0x18/0x34
>>>>>>>>>>>> panic+0x14c/0x32c
>>>>>>>>>>>> nmi_panic+0x58/0x7c
>>>>>>>>>>>> arm64_serror_panic+0x78/0x84
>>>>>>>>>>>> do_serror+0x40/0x64
>>>>>>>>>>>> el1h_64_error_handler+0x30/0x48
>>>>>>>>>>>> el1h_64_error+0x68/0x6c
>>>>>>>>>>>> __cmpxchg_case_acq_32+0x14/0x2c
>>>>>>>>>>>> _raw_spin_lock_irqsave+0x38/0x4c
>>>>>>>
>>>>>>> You know, after re-reading the trace, I could not help but notice
>>>>>>> that
>>>>>>> the issue seems to be related to completion/timer/spinlock memory
>>>>>>> becoming unavailable rather than disabling the main link clock.
>>>>>>> See, the SError comes in the spin_lock path, not during register
>>>>>>> read.
>>>>>>>
>>>>>>> Thus I think the commit message is a bit misleading.
>>>>>>>
>>>>>>
>>>>>> No, this issue is due to unclocked access. Please check this part
>>>>>> of the
>>>>>> stack:
>>>>>
>>>>> Well, if it were for the unlocked access, we would see SError on the
>>>>> register access, wouldn't we? However in this case the SError comes
>>>>> from the raw spinlock code.
>>>>
>>>> This is not uncommon. With unclocked access, we have seen in the past
>>>> that sometimes the stack is off by one line. The fact that this issue
>>>> got resolved even with the older version of the patch
>>>> https://patchwork.freedesktop.org/patch/496984/ is pointing towards an
>>>> unclocked access and not the dp/dp->ctrl memory pointers.
>>>
>>> As far as I understood, the bug is reproducible. Just to make me feel
>>> safe, can we please:
>>> - either have a trace which shows when the clocks are disabled (or
>>> not enabled)
>>> - or make sure that keeping the mainlink clock on would also mitigate
>>> the issue?
>>
>> Yes, this trace is already available with all the drm_dbg_dp messages
>> enabled. Please refer to the attachment named
>> 2022-08-15-dmesg-drm-4K-crash.txt in the bug
>> https://gitlab.freedesktop.org/drm/msm/-/issues/17.
>>
>> You can jump to this section of the log.
>>
>> [ 99.191216] msm_dpu ae01000.mdp: [drm:dp_display_host_phy_exit]
>> type=10 core_init=1 phy_init=1
>> [ 99.192354] [drm:dp_ctrl_phy_exit] phy=00000000b9b91350 init=0
>> power_on=0
>> [ 99.192369] msm_dpu ae01000.mdp:
>> [drm:dp_display_disable.constprop.0.isra.0] sink count: 1
>>
>> Here is the dp_display_disable() you were looking for.
>>
>> [ 99.192378] msm_dpu ae01000.mdp: [drm:dp_bridge_post_disable]
>> type=10 Done
>> [ 99.192389] msm_dpu ae01000.mdp:
>> [drm:drm_atomic_helper_commit_modeset_disables] disabling
>> [CRTC:60:crtc-1]
>> [ 99.192561] [drm:dpu_crtc_disable] no frames pending
>> [ 99.192571] [drm:dpu_core_perf_crtc_update] crtc:60 stop_req:1
>> core_clk:200000000
>> [ 99.192581] [drm:dpu_core_perf_crtc_update] crtc=60 disable
>> [ 99.192588] [drm:_dpu_core_perf_crtc_update_bus] crtc=59 bw=0 paths:1
>> [ 99.192595] [drm:_dpu_core_perf_crtc_update_bus] crtc=60 bw=0 paths:1
>> [ 99.192700] [drm:dpu_core_perf_crtc_update] clk:200000000
>> [ 99.192714] [drm:dpu_core_perf_crtc_update] update clk rate =
>> 200000000 HZ
>> [ 99.192729] msm_dpu ae01000.mdp:
>> [drm:drm_atomic_helper_commit_modeset_disables] modeset on
>> [ENCODER:33:TMDS-33]
>> [ 99.192738] [drm:dpu_encoder_virt_atomic_mode_set] enc33
>> [ 99.192749] [drm:dpu_crtc_atomic_begin] crtc59
>>>
>>>>
>>>>>
>>>>>> >>>>>> wait_for_completion_timeout+0x2c/0x54
>>>>>> >>>>>> dp_ctrl_push_idle+0x40/0x88
>>>>>> >>>>>> dp_bridge_disable+0x24/0x30
>>>>>> >>>>>> drm_atomic_bridge_chain_disable+0x90/0xbc
>>>>>> >>>>>> drm_atomic_helper_commit_modeset_disables+0x198/0x444
>>>>>> >>>>>> msm_atomic_commit_tail+0x1d0/0x374
>>>>>> >>>>>> commit_tail+0x80/0x108
>>>>>> >>>>>> drm_atomic_helper_commit+0x118/0x11c
>>>>>> >>>>>> drm_atomic_commit+0xb4/0xe0
>>>>>> >>>>>> drm_client_modeset_commit_atomic+0x184/0x224
>>>>>> >>>>>> drm_client_modeset_commit_locked+0x58/0x160
>>>>>> >>>>>> drm_client_modeset_commit+0x3c/0x64
>>>>>>
>>>>>>> Can we please get a trace checking which calls were actually made
>>>>>>> for
>>>>>>> the dp bridge and if the dp/dp->ctrl memory pointers are correct?
>>>>>>>
>>>>>>> I do not see the dp_display_disable() being called. Maybe I just
>>>>>>> missed
>>>>>>> the call.
>>>>>>>
>>>>>>
>>>>>> Yes it is called, please refer to the above part of the stack that I
>>>>>> have pasted.
>>>>>
>>>>> The stacktrace mentions dp_bridge_disable(), not dp_display_disable()
>>>>> (which I asked for).
>>>>>
>>>>
>>>> So whats happening here is the crash is happening in
>>>> dp_bridge_disable().
>>>>
>>>> dp_display_disable() is called from post_disable() thats why it doesnt
>>>> show up in the stack.
>>>>
>>>
>>> Yes. But the mainlink clocks are disabled in dp_display_disable()
>>> that's why I'm asking if the function was called at all.
>>
>> Now, I see why you were asking about dp_display_disable(). So
>> basically your question is that when did dp_display_disable() happen
>> that disabled the clocks causing this issue.
>>
>> dp_display_disable() happened when the cable was disconnected as shown
>> in the above section of the logs.
>>
>> We also sent the disconnected uevent to the usermode. But this commit
>> is happening from the drm_lastclose() context which doesnt check the
>> connection status.
>>
>> This leads to a commit after the cable has been disconnected causing
>> the unclocked access.
>>
>> You can refer this log and comment if something is still not clear to
>> you.
>
> I have spent some time comparing the log and the programming logic.
>
> I found what I was looking for: a safeguard for not doing the disable
> twice. The disable_outputs() function, the one which calls
> drm_atomic_bridge_chain_disable() has a logical check which should have
> acted as a safety net here: it checks whether crtc_needs_disable().
>
> Can you please doublecheck why doesn't it reflect the fact that CRTC
> doesn't need disabling as it has been already disabled. If I understand
> correctly this boils down to CRTC's old_state->active being set, while
> the CRTC has been effectively disabled.
>
Yes, I had investigated this angle too. Please check my analysis here:
https://patchwork.freedesktop.org/patch/496984/#comment_896107
crtc_state->active is controlled by the usermode setting the "active"
property on the CRTC AFAICT, it is not a driver managed variable.
From the user report, there was a usermode crash. So it is entirely
possible that usermode did not reset before crashing this allowing the
second disable.
The only thing I dont have for you is a log proving this because by
default there is no DRM trace for this flow from UAPI.
So after sharing this analysis, Stephen mentioned that usermode should
not allow DRM to crash like this which I agreed with and hence we wanted
to avoid this scenario with this patch.
Let me know if you think this analysis still needs to be checked and why.
^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2022-08-26 16:44 UTC | newest]
Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-08-17 18:01 [PATCH] drm/msm/dp: add atomic_check to bridge ops Kuogee Hsieh
2022-08-22 16:18 ` Dmitry Baryshkov
2022-08-22 16:38 ` Abhinav Kumar
2022-08-22 16:49 ` Dmitry Baryshkov
2022-08-22 17:32 ` Abhinav Kumar
2022-08-22 18:33 ` Dmitry Baryshkov
2022-08-23 22:07 ` Abhinav Kumar
2022-08-23 22:18 ` Abhinav Kumar
2022-08-23 22:41 ` Dmitry Baryshkov
2022-08-23 22:59 ` Abhinav Kumar
2022-08-24 8:25 ` Dmitry Baryshkov
2022-08-24 19:16 ` Abhinav Kumar
2022-08-26 8:19 ` Dmitry Baryshkov
2022-08-26 16:39 ` Abhinav Kumar
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