* [PATCH 0/3] drm/i915: MST link training locking and cleanups
@ 2015-08-27 15:36 ville.syrjala
2015-08-27 15:36 ` [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex ville.syrjala
` (2 more replies)
0 siblings, 3 replies; 9+ messages in thread
From: ville.syrjala @ 2015-08-27 15:36 UTC (permalink / raw)
To: intel-gfx
From: Ville Syrjälä <ville.syrjala@linux.intel.com>
While glancing at the MST hpd code I noticed we have no locking in there
to protect the link retraining against a concurrent modeset. So I added some,
and then ocd struct and had to clean up the code a bit.
These patches are available at
git://github.com/vsyrjala/linux.git mst_fixes_cleanups
In the repo I've also included an earlier patch which attempts to enable
the DDI PLL for MST on SKL [1]
[1] http://lists.freedesktop.org/archives/intel-gfx/2015-August/073965.html
Ville Syrjälä (3):
drm/i915: Protect MST retraining with connection_mutex
drm/i915: Flatten the mst suspend/resume functions a bit
drm/i915: Flatten intel_dp_check_mst_status()
drivers/gpu/drm/i915/intel_dp.c | 127 ++++++++++++++++++++--------------------
1 file changed, 65 insertions(+), 62 deletions(-)
--
2.4.6
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^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex
2015-08-27 15:36 [PATCH 0/3] drm/i915: MST link training locking and cleanups ville.syrjala
@ 2015-08-27 15:36 ` ville.syrjala
2015-09-03 12:11 ` Ville Syrjälä
2015-08-27 15:36 ` [PATCH 2/3] drm/i915: Flatten the mst suspend/resume functions a bit ville.syrjala
2015-08-27 15:36 ` [PATCH 3/3] drm/i915: Flatten intel_dp_check_mst_status() ville.syrjala
2 siblings, 1 reply; 9+ messages in thread
From: ville.syrjala @ 2015-08-27 15:36 UTC (permalink / raw)
To: intel-gfx
From: Ville Syrjälä <ville.syrjala@linux.intel.com>
Grab the connection_mutex around MSR link retraining to protect it
against a concurrent modeset. We already do the same for SST.
DP hpd_pulse can still otherwise race against modeset and ->detect(), so
it's not clear what will happen when both want to scribble into eg.
intel_dp->dpcd[] at the same time. But sorting it all out requires way
more thought than I'm willing to expend now.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
drivers/gpu/drm/i915/intel_dp.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 9e90a2b..1259c9b 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4391,6 +4391,7 @@ update_status:
static int
intel_dp_check_mst_status(struct intel_dp *intel_dp)
{
+ struct drm_device *dev = dp_to_dig_port(intel_dp)->base.base.dev;
bool bret;
if (intel_dp->is_mst) {
@@ -4402,6 +4403,8 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
go_again:
if (bret == true) {
+ drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+
/* check link status - esi[10] = 0x200c */
if (intel_dp->active_mst_links &&
!drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
@@ -4411,6 +4414,8 @@ go_again:
intel_dp_stop_link_train(intel_dp);
}
+ drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
DRM_DEBUG_KMS("got esi %3ph\n", esi);
ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
--
2.4.6
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^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 2/3] drm/i915: Flatten the mst suspend/resume functions a bit
2015-08-27 15:36 [PATCH 0/3] drm/i915: MST link training locking and cleanups ville.syrjala
2015-08-27 15:36 ` [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex ville.syrjala
@ 2015-08-27 15:36 ` ville.syrjala
2015-09-16 12:28 ` Maarten Lankhorst
2015-08-27 15:36 ` [PATCH 3/3] drm/i915: Flatten intel_dp_check_mst_status() ville.syrjala
2 siblings, 1 reply; 9+ messages in thread
From: ville.syrjala @ 2015-08-27 15:36 UTC (permalink / raw)
To: intel-gfx
From: Ville Syrjälä <ville.syrjala@linux.intel.com>
I'm not a fan of deeply nested ifs. Just pull most of the conditions
into a single place to flatten things a bit.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
drivers/gpu/drm/i915/intel_dp.c | 32 ++++++++++++++------------------
1 file changed, 14 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 1259c9b..6c34784 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -6252,15 +6252,14 @@ void intel_dp_mst_suspend(struct drm_device *dev)
/* disable MST */
for (i = 0; i < I915_MAX_PORTS; i++) {
struct intel_digital_port *intel_dig_port = dev_priv->hotplug.irq_port[i];
- if (!intel_dig_port)
+
+ if (!intel_dig_port ||
+ intel_dig_port->base.type != INTEL_OUTPUT_DISPLAYPORT ||
+ !intel_dig_port->dp.can_mst)
continue;
- if (intel_dig_port->base.type == INTEL_OUTPUT_DISPLAYPORT) {
- if (!intel_dig_port->dp.can_mst)
- continue;
- if (intel_dig_port->dp.is_mst)
- drm_dp_mst_topology_mgr_suspend(&intel_dig_port->dp.mst_mgr);
- }
+ if (intel_dig_port->dp.is_mst)
+ drm_dp_mst_topology_mgr_suspend(&intel_dig_port->dp.mst_mgr);
}
}
@@ -6271,18 +6270,15 @@ void intel_dp_mst_resume(struct drm_device *dev)
for (i = 0; i < I915_MAX_PORTS; i++) {
struct intel_digital_port *intel_dig_port = dev_priv->hotplug.irq_port[i];
- if (!intel_dig_port)
- continue;
- if (intel_dig_port->base.type == INTEL_OUTPUT_DISPLAYPORT) {
- int ret;
+ int ret;
- if (!intel_dig_port->dp.can_mst)
- continue;
+ if (!intel_dig_port ||
+ intel_dig_port->base.type != INTEL_OUTPUT_DISPLAYPORT ||
+ !intel_dig_port->dp.can_mst)
+ continue;
- ret = drm_dp_mst_topology_mgr_resume(&intel_dig_port->dp.mst_mgr);
- if (ret != 0) {
- intel_dp_check_mst_status(&intel_dig_port->dp);
- }
- }
+ ret = drm_dp_mst_topology_mgr_resume(&intel_dig_port->dp.mst_mgr);
+ if (ret)
+ intel_dp_check_mst_status(&intel_dig_port->dp);
}
}
--
2.4.6
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^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 3/3] drm/i915: Flatten intel_dp_check_mst_status()
2015-08-27 15:36 [PATCH 0/3] drm/i915: MST link training locking and cleanups ville.syrjala
2015-08-27 15:36 ` [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex ville.syrjala
2015-08-27 15:36 ` [PATCH 2/3] drm/i915: Flatten the mst suspend/resume functions a bit ville.syrjala
@ 2015-08-27 15:36 ` ville.syrjala
2015-09-16 13:07 ` Maarten Lankhorst
2 siblings, 1 reply; 9+ messages in thread
From: ville.syrjala @ 2015-08-27 15:36 UTC (permalink / raw)
To: intel-gfx
From: Ville Syrjälä <ville.syrjala@linux.intel.com>
Restructure intel_dp_check_mst_status() to be more straightforward to
read.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
drivers/gpu/drm/i915/intel_dp.c | 92 +++++++++++++++++++++--------------------
1 file changed, 47 insertions(+), 45 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 6c34784..033ee20 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4392,62 +4392,64 @@ static int
intel_dp_check_mst_status(struct intel_dp *intel_dp)
{
struct drm_device *dev = dp_to_dig_port(intel_dp)->base.base.dev;
+ u8 esi[16];
bool bret;
- if (intel_dp->is_mst) {
- u8 esi[16] = { 0 };
- int ret = 0;
- int retry;
+ if (!intel_dp->is_mst)
+ return -EINVAL;
+
+ bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
+
+ if (!bret) {
+ DRM_DEBUG_KMS("failed to get ESI - device may have failed\n");
+ intel_dp->is_mst = false;
+ drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
+ /* send a hotplug event */
+ drm_kms_helper_hotplug_event(dev);
+
+ return -EINVAL;
+ }
+
+ for (;;) {
bool handled;
- bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
-go_again:
- if (bret == true) {
+ int retry;
+ int ret;
- drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+ drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
- /* check link status - esi[10] = 0x200c */
- if (intel_dp->active_mst_links &&
- !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
- DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
- intel_dp_start_link_train(intel_dp);
- intel_dp_complete_link_train(intel_dp);
- intel_dp_stop_link_train(intel_dp);
- }
+ /* check link status - esi[10] = 0x200c */
+ if (intel_dp->active_mst_links &&
+ !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
+ DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
+ intel_dp_start_link_train(intel_dp);
+ intel_dp_complete_link_train(intel_dp);
+ intel_dp_stop_link_train(intel_dp);
+ }
- drm_modeset_unlock(&dev->mode_config.connection_mutex);
- DRM_DEBUG_KMS("got esi %3ph\n", esi);
- ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
-
- if (handled) {
- for (retry = 0; retry < 3; retry++) {
- int wret;
- wret = drm_dp_dpcd_write(&intel_dp->aux,
- DP_SINK_COUNT_ESI+1,
- &esi[1], 3);
- if (wret == 3) {
- break;
- }
- }
+ drm_modeset_unlock(&dev->mode_config.connection_mutex);
- bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
- if (bret == true) {
- DRM_DEBUG_KMS("got esi2 %3ph\n", esi);
- goto go_again;
- }
- } else
- ret = 0;
+ DRM_DEBUG_KMS("got esi %3ph\n", esi);
+ ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
- return ret;
- } else {
- struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
- DRM_DEBUG_KMS("failed to get ESI - device may have failed\n");
- intel_dp->is_mst = false;
- drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
- /* send a hotplug event */
- drm_kms_helper_hotplug_event(intel_dig_port->base.base.dev);
+ if (!handled)
+ return 0;
+
+ for (retry = 0; retry < 3; retry++) {
+ int wret = drm_dp_dpcd_write(&intel_dp->aux,
+ DP_SINK_COUNT_ESI+1,
+ &esi[1], 3);
+ if (wret == 3)
+ break;
}
+
+ bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
+ if (!bret)
+ return ret;
+
+ DRM_DEBUG_KMS("got esi2 %3ph\n", esi);
}
+
return -EINVAL;
}
--
2.4.6
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^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex
2015-08-27 15:36 ` [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex ville.syrjala
@ 2015-09-03 12:11 ` Ville Syrjälä
2015-09-16 11:48 ` Maarten Lankhorst
0 siblings, 1 reply; 9+ messages in thread
From: Ville Syrjälä @ 2015-09-03 12:11 UTC (permalink / raw)
To: intel-gfx
On Thu, Aug 27, 2015 at 06:36:48PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Grab the connection_mutex around MSR link retraining to protect it
> against a concurrent modeset. We already do the same for SST.
>
> DP hpd_pulse can still otherwise race against modeset and ->detect(), so
> it's not clear what will happen when both want to scribble into eg.
> intel_dp->dpcd[] at the same time. But sorting it all out requires way
> more thought than I'm willing to expend now.
Actually I suppose this might not work out so well after all. I suppose
MST depends on short HPDs during modeset due to the sideband stuff.
So if we want to grab modeset locks for retraining, I suppose we'd
need to move the retraining to happen from .hot_plug() which gets run
from the other hotplug work, and so wouldn't interfere with sideband.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 9e90a2b..1259c9b 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4391,6 +4391,7 @@ update_status:
> static int
> intel_dp_check_mst_status(struct intel_dp *intel_dp)
> {
> + struct drm_device *dev = dp_to_dig_port(intel_dp)->base.base.dev;
> bool bret;
>
> if (intel_dp->is_mst) {
> @@ -4402,6 +4403,8 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
> go_again:
> if (bret == true) {
>
> + drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +
> /* check link status - esi[10] = 0x200c */
> if (intel_dp->active_mst_links &&
> !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
> @@ -4411,6 +4414,8 @@ go_again:
> intel_dp_stop_link_train(intel_dp);
> }
>
> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> DRM_DEBUG_KMS("got esi %3ph\n", esi);
> ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
>
> --
> 2.4.6
--
Ville Syrjälä
Intel OTC
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex
2015-09-03 12:11 ` Ville Syrjälä
@ 2015-09-16 11:48 ` Maarten Lankhorst
2015-09-23 8:01 ` Daniel Vetter
0 siblings, 1 reply; 9+ messages in thread
From: Maarten Lankhorst @ 2015-09-16 11:48 UTC (permalink / raw)
To: Ville Syrjälä, intel-gfx
Hey,
Op 03-09-15 om 14:11 schreef Ville Syrjälä:
> On Thu, Aug 27, 2015 at 06:36:48PM +0300, ville.syrjala@linux.intel.com wrote:
>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>
>> Grab the connection_mutex around MSR link retraining to protect it
>> against a concurrent modeset. We already do the same for SST.
>>
>> DP hpd_pulse can still otherwise race against modeset and ->detect(), so
>> it's not clear what will happen when both want to scribble into eg.
>> intel_dp->dpcd[] at the same time. But sorting it all out requires way
>> more thought than I'm willing to expend now.
> Actually I suppose this might not work out so well after all. I suppose
> MST depends on short HPDs during modeset due to the sideband stuff.
>
> So if we want to grab modeset locks for retraining, I suppose we'd
> need to move the retraining to happen from .hot_plug() which gets run
> from the other hotplug work, and so wouldn't interfere with sideband.
>
I think it would be better to have a per encoder mutex. In the future we may want to run modeset
disable/enable async, in which case it may not hold the connection_mutex.
If we do decide on a separate mutex then it would also be useful to also think about how to
protect intel_mst_*(dis,en)able_dp. :)
~Maarten
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/3] drm/i915: Flatten the mst suspend/resume functions a bit
2015-08-27 15:36 ` [PATCH 2/3] drm/i915: Flatten the mst suspend/resume functions a bit ville.syrjala
@ 2015-09-16 12:28 ` Maarten Lankhorst
0 siblings, 0 replies; 9+ messages in thread
From: Maarten Lankhorst @ 2015-09-16 12:28 UTC (permalink / raw)
To: ville.syrjala, intel-gfx
Hey,
Op 27-08-15 om 17:36 schreef ville.syrjala@linux.intel.com:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> I'm not a fan of deeply nested ifs. Just pull most of the conditions
> into a single place to flatten things a bit.
I like flat..
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 3/3] drm/i915: Flatten intel_dp_check_mst_status()
2015-08-27 15:36 ` [PATCH 3/3] drm/i915: Flatten intel_dp_check_mst_status() ville.syrjala
@ 2015-09-16 13:07 ` Maarten Lankhorst
0 siblings, 0 replies; 9+ messages in thread
From: Maarten Lankhorst @ 2015-09-16 13:07 UTC (permalink / raw)
To: ville.syrjala, intel-gfx
Op 27-08-15 om 17:36 schreef ville.syrjala@linux.intel.com:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Restructure intel_dp_check_mst_status() to be more straightforward to
> read.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 92 +++++++++++++++++++++--------------------
> 1 file changed, 47 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 6c34784..033ee20 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> <snip>
> + for (;;) {
> bool handled;
> - bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
> -go_again:
> - if (bret == true) {
> + int retry;
> + int ret;
>
> - drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> + drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
>
> - /* check link status - esi[10] = 0x200c */
> - if (intel_dp->active_mst_links &&
> - !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
> - DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
> - intel_dp_start_link_train(intel_dp);
> - intel_dp_complete_link_train(intel_dp);
> - intel_dp_stop_link_train(intel_dp);
> - }
> + /* check link status - esi[10] = 0x200c */
> + if (intel_dp->active_mst_links &&
> + !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
> + DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
> + intel_dp_start_link_train(intel_dp);
> + intel_dp_complete_link_train(intel_dp);
> + intel_dp_stop_link_train(intel_dp);
> + }
>
> - drm_modeset_unlock(&dev->mode_config.connection_mutex);
>
> - DRM_DEBUG_KMS("got esi %3ph\n", esi);
> - ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
> -
> - if (handled) {
> - for (retry = 0; retry < 3; retry++) {
> - int wret;
> - wret = drm_dp_dpcd_write(&intel_dp->aux,
> - DP_SINK_COUNT_ESI+1,
> - &esi[1], 3);
> - if (wret == 3) {
> - break;
> - }
> - }
> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
>
> - bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
> - if (bret == true) {
> - DRM_DEBUG_KMS("got esi2 %3ph\n", esi);
> - goto go_again;
> - }
> - } else
> - ret = 0;
> + DRM_DEBUG_KMS("got esi %3ph\n", esi);
> + ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
>
> - return ret;
> - } else {
> - struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> - DRM_DEBUG_KMS("failed to get ESI - device may have failed\n");
> - intel_dp->is_mst = false;
> - drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
> - /* send a hotplug event */
> - drm_kms_helper_hotplug_event(intel_dig_port->base.base.dev);
> + if (!handled)
> + return 0;
> +
> + for (retry = 0; retry < 3; retry++) {
> + int wret = drm_dp_dpcd_write(&intel_dp->aux,
> + DP_SINK_COUNT_ESI+1,
> + &esi[1], 3);
> + if (wret == 3)
> + break;
> }
> +
> + bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
> + if (!bret)
> + return ret;
^This seemed like a bug the first time I looked at it with the indent changes.
Original indent with if (handled) {.. } seems better here, but with a continue instead of a goto.
I think a single return ret; would make it more clear when the loop finishes.
The original code sets ret = 0 when handled = false, but looking a drm_dp_mst_hpd_irq
this is unneeded.
> +
> + DRM_DEBUG_KMS("got esi2 %3ph\n", esi);
> }
> +
> return -EINVAL;
Can this -EINVAL be removed? It cannot be reached any more.
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex
2015-09-16 11:48 ` Maarten Lankhorst
@ 2015-09-23 8:01 ` Daniel Vetter
0 siblings, 0 replies; 9+ messages in thread
From: Daniel Vetter @ 2015-09-23 8:01 UTC (permalink / raw)
To: Maarten Lankhorst; +Cc: intel-gfx
On Wed, Sep 16, 2015 at 01:48:49PM +0200, Maarten Lankhorst wrote:
> Hey,
>
> Op 03-09-15 om 14:11 schreef Ville Syrjälä:
> > On Thu, Aug 27, 2015 at 06:36:48PM +0300, ville.syrjala@linux.intel.com wrote:
> >> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>
> >> Grab the connection_mutex around MSR link retraining to protect it
> >> against a concurrent modeset. We already do the same for SST.
> >>
> >> DP hpd_pulse can still otherwise race against modeset and ->detect(), so
> >> it's not clear what will happen when both want to scribble into eg.
> >> intel_dp->dpcd[] at the same time. But sorting it all out requires way
> >> more thought than I'm willing to expend now.
> > Actually I suppose this might not work out so well after all. I suppose
> > MST depends on short HPDs during modeset due to the sideband stuff.
> >
> > So if we want to grab modeset locks for retraining, I suppose we'd
> > need to move the retraining to happen from .hot_plug() which gets run
> > from the other hotplug work, and so wouldn't interfere with sideband.
> >
> I think it would be better to have a per encoder mutex. In the future we may want to run modeset
> disable/enable async, in which case it may not hold the connection_mutex.
>
> If we do decide on a separate mutex then it would also be useful to also think about how to
> protect intel_mst_*(dis,en)able_dp. :)
We need to sync re-training with any other modeset work. Which means
another thing to get right for async modesets.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2015-09-23 7:58 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-08-27 15:36 [PATCH 0/3] drm/i915: MST link training locking and cleanups ville.syrjala
2015-08-27 15:36 ` [PATCH 1/3] drm/i915: Protect MST retraining with connection_mutex ville.syrjala
2015-09-03 12:11 ` Ville Syrjälä
2015-09-16 11:48 ` Maarten Lankhorst
2015-09-23 8:01 ` Daniel Vetter
2015-08-27 15:36 ` [PATCH 2/3] drm/i915: Flatten the mst suspend/resume functions a bit ville.syrjala
2015-09-16 12:28 ` Maarten Lankhorst
2015-08-27 15:36 ` [PATCH 3/3] drm/i915: Flatten intel_dp_check_mst_status() ville.syrjala
2015-09-16 13:07 ` Maarten Lankhorst
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