* [PATCH v3] i2c: lpi2c: cache peripheral clock rate
@ 2023-03-10 13:08 A. Sverdlin
2023-04-21 13:48 ` Alexander Stein
2023-04-24 8:08 ` Alexander Stein
0 siblings, 2 replies; 14+ messages in thread
From: A. Sverdlin @ 2023-03-10 13:08 UTC (permalink / raw)
To: NXP Linux Team
Cc: Alexander Sverdlin, Alexander Stein, Dong Aisheng, Shawn Guo,
Sascha Hauer, Pengutronix Kernel Team, Fabio Estevam, linux-i2c,
linux-arm-kernel, linux-kernel
From: Alexander Sverdlin <alexander.sverdlin@siemens.com>
One of the reasons to do it is to save some CPU cycles on cpu_freq_get()
under mutex. The second reason if the (false-positive) lockdep splat caused
by the recursive feature of the "prepare_lock" (one clock instance is I2C
peripheral clock and another is pcf85063 RTC as clock provider):
======================================================
WARNING: possible circular locking dependency detected
5.15.71+... #1 Tainted: G O
------------------------------------------------------
fs-value/2332 is trying to acquire lock:
ffff8000096cae08 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock
but task is already holding lock:
ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at: i2c_adapter_lock_bus
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (i2c_register_adapter){+.+.}-{3:3}:
lock_acquire
rt_mutex_lock_nested
i2c_adapter_lock_bus
i2c_transfer
regmap_i2c_read
_regmap_raw_read
_regmap_bus_read
_regmap_read
regmap_read
pcf85063_probe
i2c_device_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
device_add
device_register
i2c_new_client_device
of_i2c_register_devices
i2c_register_adapter
__i2c_add_numbered_adapter
i2c_add_adapter
lpi2c_imx_probe
platform_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
deferred_probe_work_func
process_one_work
worker_thread
kthread
ret_from_fork
-> #1 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
lock_acquire
__mutex_lock
mutex_lock_nested
regmap_lock_mutex
regmap_read
pcf85063_clkout_recalc_rate
__clk_register
devm_clk_register
pcf85063_probe
i2c_device_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
device_add
device_register
i2c_new_client_device
of_i2c_register_devices
i2c_register_adapter
__i2c_add_numbered_adapter
i2c_add_adapter
lpi2c_imx_probe
platform_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
deferred_probe_work_func
process_one_work
worker_thread
kthread
ret_from_fork
-> #0 (prepare_lock){+.+.}-{3:3}:
__lock_acquire
lock_acquire.part.0
lock_acquire
__mutex_lock
mutex_lock_nested
clk_prepare_lock
clk_get_rate
lpi2c_imx_xfer
__i2c_transfer
i2c_transfer
regmap_i2c_read
_regmap_raw_read
regmap_raw_read
regmap_bulk_read
at24_read
nvmem_reg_read
bin_attr_nvmem_read
sysfs_kf_bin_read
kernfs_fop_read_iter
new_sync_read
vfs_read
ksys_read
__arm64_sys_read
invoke_syscall
...
other info that might help us debug this:
Chain exists of:
prepare_lock --> rtc_pcf85063:560:(&config->regmap)->lock --> i2c_register_adapter
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(i2c_register_adapter);
lock(rtc_pcf85063:560:(&config->regmap)->lock);
lock(i2c_register_adapter);
lock(prepare_lock);
*** DEADLOCK ***
4 locks held by .../2332:
#0: ffff0000146eb288 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_read_iter
#1: ffff000010fe4400 (kn->active#72){.+.+}-{0:0}, at: kernfs_fop_read_iter
#2: ffff0000110168e8 (&at24->lock){+.+.}-{3:3}, at: at24_read
#3: ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at: i2c_adapter_lock_bus
stack backtrace:
CPU: 1 PID: 2332 Comm: ... Tainted: G O 5.15.71+... #1
Hardware name: ... (DT)
Call trace:
dump_backtrace
show_stack
dump_stack_lvl
dump_stack
print_circular_bug
check_noncircular
__lock_acquire
lock_acquire.part.0
lock_acquire
__mutex_lock
mutex_lock_nested
clk_prepare_lock
clk_get_rate
lpi2c_imx_xfer
__i2c_transfer
i2c_transfer
regmap_i2c_read
_regmap_raw_read
regmap_raw_read
regmap_bulk_read
at24_read
nvmem_reg_read
bin_attr_nvmem_read
sysfs_kf_bin_read
kernfs_fop_read_iter
new_sync_read
vfs_read
ksys_read
__arm64_sys_read
invoke_syscall
...
Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
drivers/i2c/busses/i2c-imx-lpi2c.c | 33 +++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)
Changelog:
v3: fixed build error reported by kernel test robot <lkp@intel.com>
https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/
v2: added clk_notifier as Alexander suggested
diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 188f2a36d2fd6..5f1d1d4e018bd 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -100,6 +100,8 @@ struct lpi2c_imx_struct {
__u8 *rx_buf;
__u8 *tx_buf;
struct completion complete;
+ struct notifier_block clk_change_nb;
+ unsigned int rate_per;
unsigned int msglen;
unsigned int delivered;
unsigned int block_data;
@@ -198,24 +200,37 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx)
} while (1);
}
+static int lpi2c_imx_clk_change_cb(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ struct clk_notifier_data *ndata = data;
+ struct lpi2c_imx_struct *lpi2c_imx = container_of(nb,
+ struct lpi2c_imx_struct,
+ clk_change_nb);
+
+ if (action & POST_RATE_CHANGE)
+ lpi2c_imx->rate_per = ndata->new_rate;
+
+ return NOTIFY_OK;
+}
+
/* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
{
u8 prescale, filt, sethold, clkhi, clklo, datavd;
- unsigned int clk_rate, clk_cycle;
+ unsigned int clk_cycle;
enum lpi2c_imx_pincfg pincfg;
unsigned int temp;
lpi2c_imx_set_mode(lpi2c_imx);
- clk_rate = clk_get_rate(lpi2c_imx->clks[0].clk);
if (lpi2c_imx->mode == HS || lpi2c_imx->mode == ULTRA_FAST)
filt = 0;
else
filt = 2;
for (prescale = 0; prescale <= 7; prescale++) {
- clk_cycle = clk_rate / ((1 << prescale) * lpi2c_imx->bitrate)
+ clk_cycle = lpi2c_imx->rate_per / ((1 << prescale) * lpi2c_imx->bitrate)
- 3 - (filt >> 1);
clkhi = (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1);
clklo = clk_cycle - clkhi;
@@ -588,6 +603,18 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
if (ret)
return ret;
+ lpi2c_imx->clk_change_nb.notifier_call = lpi2c_imx_clk_change_cb;
+ ret = devm_clk_notifier_register(&pdev->dev, lpi2c_imx->clks[0].clk,
+ &lpi2c_imx->clk_change_nb);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret,
+ "can't register peripheral clock notifier\n");
+ lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk);
+ if (!lpi2c_imx->rate_per) {
+ dev_err(&pdev->dev, "can't get I2C peripheral clock rate\n");
+ return -EINVAL;
+ }
+
pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
pm_runtime_use_autosuspend(&pdev->dev);
pm_runtime_get_noresume(&pdev->dev);
--
2.34.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-03-10 13:08 [PATCH v3] i2c: lpi2c: cache peripheral clock rate A. Sverdlin
@ 2023-04-21 13:48 ` Alexander Stein
2023-04-21 13:59 ` Marc Kleine-Budde
` (3 more replies)
2023-04-24 8:08 ` Alexander Stein
1 sibling, 4 replies; 14+ messages in thread
From: Alexander Stein @ 2023-04-21 13:48 UTC (permalink / raw)
To: NXP Linux Team, A. Sverdlin
Cc: Alexander Sverdlin, Dong Aisheng, Shawn Guo, Sascha Hauer,
Pengutronix Kernel Team, Fabio Estevam, linux-i2c,
linux-arm-kernel, linux-kernel
Hi,
sorry for the delay.
Am Freitag, 10. März 2023, 14:08:15 CEST schrieb A. Sverdlin:
> From: Alexander Sverdlin <alexander.sverdlin@siemens.com>
>
> One of the reasons to do it is to save some CPU cycles on cpu_freq_get()
> under mutex. The second reason if the (false-positive) lockdep splat caused
> by the recursive feature of the "prepare_lock" (one clock instance is I2C
> peripheral clock and another is pcf85063 RTC as clock provider):
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.15.71+... #1 Tainted: G O
> ------------------------------------------------------
> fs-value/2332 is trying to acquire lock:
> ffff8000096cae08 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock
>
> but task is already holding lock:
> ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus
>
> which lock already depends on the new lock.
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (i2c_register_adapter){+.+.}-{3:3}:
> lock_acquire
> rt_mutex_lock_nested
> i2c_adapter_lock_bus
> i2c_transfer
> regmap_i2c_read
> _regmap_raw_read
> _regmap_bus_read
> _regmap_read
> regmap_read
> pcf85063_probe
> i2c_device_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> device_add
> device_register
> i2c_new_client_device
> of_i2c_register_devices
> i2c_register_adapter
> __i2c_add_numbered_adapter
> i2c_add_adapter
> lpi2c_imx_probe
> platform_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> deferred_probe_work_func
> process_one_work
> worker_thread
> kthread
> ret_from_fork
>
> -> #1 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
> lock_acquire
> __mutex_lock
> mutex_lock_nested
> regmap_lock_mutex
> regmap_read
> pcf85063_clkout_recalc_rate
> __clk_register
> devm_clk_register
> pcf85063_probe
> i2c_device_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> device_add
> device_register
> i2c_new_client_device
> of_i2c_register_devices
> i2c_register_adapter
> __i2c_add_numbered_adapter
> i2c_add_adapter
> lpi2c_imx_probe
> platform_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> deferred_probe_work_func
> process_one_work
> worker_thread
> kthread
> ret_from_fork
>
> -> #0 (prepare_lock){+.+.}-{3:3}:
> __lock_acquire
> lock_acquire.part.0
> lock_acquire
> __mutex_lock
> mutex_lock_nested
> clk_prepare_lock
> clk_get_rate
> lpi2c_imx_xfer
> __i2c_transfer
> i2c_transfer
> regmap_i2c_read
> _regmap_raw_read
> regmap_raw_read
> regmap_bulk_read
> at24_read
> nvmem_reg_read
> bin_attr_nvmem_read
> sysfs_kf_bin_read
> kernfs_fop_read_iter
> new_sync_read
> vfs_read
> ksys_read
> __arm64_sys_read
> invoke_syscall
> ...
>
> other info that might help us debug this:
>
> Chain exists of:
> prepare_lock --> rtc_pcf85063:560:(&config->regmap)->lock -->
> i2c_register_adapter
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(i2c_register_adapter);
>
> lock(rtc_pcf85063:560:(&config->regmap)->lock); lock(i2c_register_adapter);
> lock(prepare_lock);
>
> *** DEADLOCK ***
>
> 4 locks held by .../2332:
> #0: ffff0000146eb288 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_read_iter
> #1: ffff000010fe4400 (kn->active#72){.+.+}-{0:0}, at: kernfs_fop_read_iter
> #2: ffff0000110168e8 (&at24->lock){+.+.}-{3:3}, at: at24_read
> #3: ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus
>
> stack backtrace:
> CPU: 1 PID: 2332 Comm: ... Tainted: G O 5.15.71+... #1
> Hardware name: ... (DT)
> Call trace:
> dump_backtrace
> show_stack
> dump_stack_lvl
> dump_stack
> print_circular_bug
> check_noncircular
> __lock_acquire
> lock_acquire.part.0
> lock_acquire
> __mutex_lock
> mutex_lock_nested
> clk_prepare_lock
> clk_get_rate
> lpi2c_imx_xfer
> __i2c_transfer
> i2c_transfer
> regmap_i2c_read
> _regmap_raw_read
> regmap_raw_read
> regmap_bulk_read
> at24_read
> nvmem_reg_read
> bin_attr_nvmem_read
> sysfs_kf_bin_read
> kernfs_fop_read_iter
> new_sync_read
> vfs_read
> ksys_read
> __arm64_sys_read
> invoke_syscall
> ...
>
> Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
> ---
> drivers/i2c/busses/i2c-imx-lpi2c.c | 33 +++++++++++++++++++++++++++---
> 1 file changed, 30 insertions(+), 3 deletions(-)
>
> Changelog:
> v3: fixed build error reported by kernel test robot <lkp@intel.com>
>
> https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/
> v2: added clk_notifier as Alexander suggested
>
> diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c
> b/drivers/i2c/busses/i2c-imx-lpi2c.c index 188f2a36d2fd6..5f1d1d4e018bd
> 100644
> --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> @@ -100,6 +100,8 @@ struct lpi2c_imx_struct {
> __u8 *rx_buf;
> __u8 *tx_buf;
> struct completion complete;
> + struct notifier_block clk_change_nb;
> + unsigned int rate_per;
> unsigned int msglen;
> unsigned int delivered;
> unsigned int block_data;
> @@ -198,24 +200,37 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct
> *lpi2c_imx) } while (1);
> }
>
> +static int lpi2c_imx_clk_change_cb(struct notifier_block *nb,
> + unsigned long action, void *data)
> +{
> + struct clk_notifier_data *ndata = data;
> + struct lpi2c_imx_struct *lpi2c_imx = container_of(nb,
> + struct
lpi2c_imx_struct,
> +
clk_change_nb);
> +
> + if (action & POST_RATE_CHANGE)
> + lpi2c_imx->rate_per = ndata->new_rate;
> +
> + return NOTIFY_OK;
> +}
> +
> /* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
> static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
> {
> u8 prescale, filt, sethold, clkhi, clklo, datavd;
> - unsigned int clk_rate, clk_cycle;
> + unsigned int clk_cycle;
> enum lpi2c_imx_pincfg pincfg;
> unsigned int temp;
>
> lpi2c_imx_set_mode(lpi2c_imx);
>
> - clk_rate = clk_get_rate(lpi2c_imx->clks[0].clk);
> if (lpi2c_imx->mode == HS || lpi2c_imx->mode == ULTRA_FAST)
> filt = 0;
> else
> filt = 2;
>
> for (prescale = 0; prescale <= 7; prescale++) {
> - clk_cycle = clk_rate / ((1 << prescale) * lpi2c_imx-
>bitrate)
> + clk_cycle = lpi2c_imx->rate_per / ((1 << prescale) *
lpi2c_imx->bitrate)
> - 3 - (filt >> 1);
> clkhi = (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1);
> clklo = clk_cycle - clkhi;
> @@ -588,6 +603,18 @@ static int lpi2c_imx_probe(struct platform_device
> *pdev) if (ret)
> return ret;
>
> + lpi2c_imx->clk_change_nb.notifier_call = lpi2c_imx_clk_change_cb;
> + ret = devm_clk_notifier_register(&pdev->dev, lpi2c_imx->clks[0].clk,
> + &lpi2c_imx->clk_change_nb);
> + if (ret)
> + return dev_err_probe(&pdev->dev, ret,
> + "can't register peripheral clock
notifier\n");
> + lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk);
> + if (!lpi2c_imx->rate_per) {
> + dev_err(&pdev->dev, "can't get I2C peripheral clock
rate\n");
> + return -EINVAL;
> + }
> +
I would switch the order of the calls to devm_clk_notifier_register() and
clk_get_rate(). AFAICS this looks like a possible lost update. The notifier
might change rate_per before the (old) value from clk_get_rate is actually
assigned.
With this change you fix the following call chain (from a kernel log)
[ 4.562396] clk_prepare_lock+0x48/0x9c
[ 4.566740] clk_get_rate+0x1c/0x74
[ 4.570736] lpi2c_imx_config+0x4c/0x190
[ 4.575167] lpi2c_imx_master_enable+0x54/0x128
[ 4.580205] lpi2c_imx_xfer+0x2c/0x3c8
Unfortuantely this was just hiding another call path from lpi2c_imx_xfer to
clk_bulk_prepare. Here is my kernel log:
[ 22.264508] ======================================================
[ 22.270697] WARNING: possible circular locking dependency detected
[ 22.276893] 6.3.0-rc7-next-20230420+ #6 Not tainted
[ 22.281782] ------------------------------------------------------
[ 22.287968] kworker/2:3/93 is trying to acquire lock:
[ 22.293034] ffff800009d38bf8 (prepare_lock){+.+.}-{3:3}, at:
clk_prepare_lock+0x48/0x9c
[ 22.301095]
[ 22.301095] but task is already holding lock:
[ 22.306942] ffff0000039ab100 (i2c_register_adapter){+.+.}-{3:3}, at:
i2c_adapter_lock_bus+0x20/0x2c
[ 22.316046]
[ 22.316046] which lock already depends on the new lock.
[ 22.316046]
[ 22.324238]
[ 22.324238] the existing dependency chain (in reverse order) is:
[ 22.331727]
[ 22.331727] -> #2 (i2c_register_adapter){+.+.}-{3:3}:
[ 22.338295] __lock_acquire+0x370/0x6e8
[ 22.342674] lock_acquire.part.0+0xcc/0x208
[ 22.347399] lock_acquire+0x94/0x14c
[ 22.351509] rt_mutex_lock_nested+0x5c/0x98
[ 22.356235] i2c_adapter_lock_bus+0x20/0x2c
[ 22.360961] i2c_transfer+0x80/0x114
[ 22.365069] regmap_i2c_read+0x5c/0xa0
[ 22.369362] _regmap_raw_read+0x110/0x2dc
[ 22.373905] _regmap_bus_read+0x40/0x74
[ 22.378274] _regmap_read+0x74/0x248
[ 22.382393] regmap_read+0x48/0x70
[ 22.386337] pcf85063_probe+0xf0/0x4f4
[ 22.390640] i2c_device_probe+0x100/0x2d4
[ 22.395206] call_driver_probe+0x28/0x15c
[ 22.399750] really_probe+0x180/0x320
[ 22.403946] __driver_probe_device+0x84/0x144
[ 22.408837] driver_probe_device+0x38/0x150
[ 22.413554] __device_attach_driver+0xcc/0x194
[ 22.418532] bus_for_each_drv+0x80/0xdc
[ 22.422910] __device_attach+0xa8/0x1f8
[ 22.426545] systemd-journald[128]: Oldest entry in /var/log/journal/
e4579cc7db6747028247b9b859e132d6/system.joural is older than the configured
file retention duration (1month), suggesting rotation.
[ 22.427278] device_initial_probe+0x10/0x18
[ 22.427290] bus_probe_device+0xa4/0xa8
[ 22.427299] device_add+0x3b0/0x508
[ 22.427311] device_register+0x1c/0x28
[ 22.427323] i2c_new_client_device+0x1c8/0x2bc
[ 22.427333] of_i2c_register_device+0xb4/0xdc
[ 22.427344] of_i2c_register_devices+0x80/0x154
[ 22.456329] systemd-journald[128]: /var/log/journal/
e4579cc7db6747028247b9b859e132d6/system.journal: Journal heaer limits reached
or header out-of-date, rotating.
[ 22.458176] i2c_register_adapter+0x184/0x4c8
[ 22.458202] __i2c_add_numbered_adapter+0x5c/0xa4
[ 22.502097] i2c_add_adapter+0xa0/0xcc
[ 22.502122] lpi2c_imx_probe+0x23c/0x350
[ 22.502135] platform_probe+0x64/0xfc
[ 22.502146] call_driver_probe+0x28/0x15c
[ 22.502155] really_probe+0x180/0x320
[ 22.502164] __driver_probe_device+0x84/0x144
[ 22.502173] driver_probe_device+0x38/0x150
[ 22.502182] __device_attach_driver+0xcc/0x194
[ 22.502191] bus_for_each_drv+0x80/0xdc
[ 22.502204] __device_attach+0xa8/0x1f8
[ 22.502212] device_initial_probe+0x10/0x18
[ 22.502222] bus_probe_device+0xa4/0xa8
[ 22.502230] deferred_probe_work_func+0xa0/0xf0
[ 22.502239] process_one_work+0x284/0x5b0
[ 22.502252] worker_thread+0x68/0x39c
[ 22.502263] kthread+0x104/0x108
[ 22.502274] ret_from_fork+0x10/0x20
[ 22.502286]
[ 22.502286] -> #1 (rtc_pcf85063:594:(&config->regmap)->lock){+.+.}-{3:3}:
[ 22.502310] __lock_acquire+0x370/0x6e8
[ 22.502322] lock_acquire.part.0+0xcc/0x208
[ 22.502332] lock_acquire+0x94/0x14c
[ 22.502341] __mutex_lock+0x9c/0x838
[ 22.502353] mutex_lock_nested+0x20/0x28
[ 22.502364] regmap_lock_mutex+0x10/0x18
[ 22.502377] regmap_read+0x38/0x70
[ 22.502389] pcf85063_clkout_recalc_rate+0x2c/0x78
[ 22.502403] __clk_core_init+0x46c/0x4e0
[ 22.502417] __clk_register+0x160/0x23c
[ 22.502429] devm_clk_register+0x58/0xb4
[ 22.502441] pcf85063_probe+0x238/0x4f4
[ 22.502451] i2c_device_probe+0x100/0x2d4
[ 22.502465] call_driver_probe+0x28/0x15c
[ 22.502473] really_probe+0x180/0x320
[ 22.502482] __driver_probe_device+0x84/0x144
[ 22.502491] driver_probe_device+0x38/0x150
[ 22.502500] __device_attach_driver+0xcc/0x194
[ 22.502509] bus_for_each_drv+0x80/0xdc
[ 22.502521] __device_attach+0xa8/0x1f8
[ 22.502530] device_initial_probe+0x10/0x18
[ 22.502539] bus_probe_device+0xa4/0xa8
[ 22.502548] device_add+0x3b0/0x508
[ 22.502559] device_register+0x1c/0x28
[ 22.502570] i2c_new_client_device+0x1c8/0x2bc
[ 22.502580] of_i2c_register_device+0xb4/0xdc
[ OK ] Started Network Time Synchronization[ 22.502589]
of_i2c_register_devices+0x80/0x154
.[ 22.502599] i2c_register_adapter+0x184/0x4c8
[ 22.502607] __i2c_add_numbered_adapter+0x5c/0xa4
[ 22.502616] i2c_add_adapter+0xa0/0xcc
[ 22.502624] lpi2c_imx_probe+0x23c/0x350
[ 22.502636] platform_probe+0x64/0xfc
[ 22.502646] call_driver_probe+0x28/0x15c
[ 22.502655] really_probe+0x180/0x320
[ 22.502663] __driver_probe_device+0x84/0x144
[ 22.502672] driver_probe_device+0x38/0x150
[ 22.502681] __device_attach_driver+0xcc/0x194
[ 22.502690] bus_for_each_drv+0x80/0xdc
[ 22.502702] __device_attach+0xa8/0x1f8
[ 22.502711] device_initial_probe+0x10/0x18
[ 22.502720] bus_probe_device+0xa4/0xa8
[ 22.502729] deferred_probe_work_func+0xa0/0xf0
[ 22.502738] process_one_work+0x284/0x5b0
[ 22.502749] worker_thread+0x68/0x39c
[ 22.502760] kthread+0x104/0x108
[ 22.502770] ret_from_fork+0x10/0x20
[ 22.502779]
[ 22.502779] -> #0 (prepare_lock){+.+.}-{3:3}:
[ 22.502799] check_prev_add+0xb0/0xc80
[ 22.502809] validate_chain+0x444/0x510
[ 22.502818] __lock_acquire+0x370/0x6e8
[ 22.502827] lock_acquire.part.0+0xcc/0x208
[ 22.502837] lock_acquire+0x94/0x14c
[ 22.502846] __mutex_lock+0x9c/0x838
[ 22.502857] mutex_lock_nested+0x20/0x28
[ 22.502867] clk_prepare_lock+0x48/0x9c
[ 22.502878] clk_prepare+0x1c/0x3c
[ 22.502890] clk_bulk_prepare+0x48/0xcc
[ 22.502899] lpi2c_runtime_resume+0x30/0x84
[ 22.502910] pm_generic_runtime_resume+0x28/0x3c
[ 22.502923] __genpd_runtime_resume+0x2c/0xa0
[ 22.502935] genpd_runtime_resume+0xbc/0x308
[ 22.502944] __rpm_callback+0x44/0x19c
[ 22.502953] rpm_callback+0x64/0x70
[ 22.502962] rpm_resume+0x438/0x6d8
[ 22.502970] __pm_runtime_resume+0x54/0xb0
[ 22.502978] lpi2c_imx_master_enable+0x24/0x128
[ 22.502989] lpi2c_imx_xfer+0x2c/0x3c8
[ 22.502999] __i2c_transfer+0xe4/0x5a0
[ 22.503008] i2c_transfer+0x90/0x114
[ 22.503016] i2c_transfer_buffer_flags+0x58/0x84
[ 22.503025] regmap_i2c_write+0x1c/0x4c
[ 22.503035] _regmap_raw_write_impl+0x7dc/0x944
[ 22.503044] _regmap_bus_raw_write+0x5c/0x74
[ 22.503052] _regmap_write+0x64/0x238
[ 22.503060] _regmap_update_bits+0x100/0x11c
[ 22.503069] regmap_update_bits_base+0x60/0x90
[ 22.503077] pca953x_gpio_set_value+0x74/0x90
[ 22.503088] gpiod_set_raw_value_commit+0x6c/0x7c
[ 22.503098] gpiod_set_value_nocheck+0x68/0x70
[ 22.503107] gpiod_set_value_cansleep+0x3c/0xa8
[ 22.503116] gpio_led_set_blocking+0x54/0x7c
[ 22.503128] set_brightness_delayed+0x90/0xd8
[ 22.503138] process_one_work+0x284/0x5b0
[ 22.503149] worker_thread+0x68/0x39c
[ 22.503160] kthread+0x104/0x108
[ 22.503169] ret_from_fork+0x10/0x20
[ 22.503179]
[ 22.503179] other info that might help us debug this:
[ 22.503179]
[ 22.503183] Chain exists of:
[ 22.503183] prepare_lock --> rtc_pcf85063:594:(&config->regmap)->lock -->
i2c_register_adapter
[ 22.503183]
[ 22.503207] Possible unsafe locking scenario:
[ 22.503207]
[ 22.503210] CPU0 CPU1
[ 22.503213] ---- ----
[ 22.503216] lock(i2c_register_adapter);
[ 22.503225] lock(rtc_pcf85063:594:(&config-
>regmap)->lock);
[ 22.503235] lock(i2c_register_adapter);
[ 22.503244] lock(prepare_lock);
[ 22.503253]
[ 22.503253] *** DEADLOCK ***
Now lpi2c_runtime_resume will call into clk_prepare() which also calls
clk_prepare_lock() (identical to clk_get_rate).
Best regards,
Alexader
> pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> pm_runtime_use_autosuspend(&pdev->dev);
> pm_runtime_get_noresume(&pdev->dev);
--
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
http://www.tq-group.com/
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-04-21 13:48 ` Alexander Stein
@ 2023-04-21 13:59 ` Marc Kleine-Budde
2023-04-24 7:03 ` Alexander Stein
2023-04-21 14:10 ` Sverdlin, Alexander
` (2 subsequent siblings)
3 siblings, 1 reply; 14+ messages in thread
From: Marc Kleine-Budde @ 2023-04-21 13:59 UTC (permalink / raw)
To: Alexander Stein
Cc: NXP Linux Team, A. Sverdlin, Dong Aisheng, Shawn Guo,
Sascha Hauer, Pengutronix Kernel Team, Fabio Estevam, linux-i2c,
linux-arm-kernel, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 611 bytes --]
On 21.04.2023 15:48:59, Alexander Stein wrote:
[...]
> Now lpi2c_runtime_resume will call into clk_prepare() which also calls
> clk_prepare_lock() (identical to clk_get_rate).
IIRC this is a general problem^w limitation of the clock framework,
clock providers cannot use clocks themselves in certain callback, e.g.
set_rate.
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung Nürnberg | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-04-21 13:48 ` Alexander Stein
2023-04-21 13:59 ` Marc Kleine-Budde
@ 2023-04-21 14:10 ` Sverdlin, Alexander
2023-05-15 9:11 ` Alexander Stein
2023-05-15 13:11 ` Sverdlin, Alexander
3 siblings, 0 replies; 14+ messages in thread
From: Sverdlin, Alexander @ 2023-04-21 14:10 UTC (permalink / raw)
To: alexander.stein, linux-imx
Cc: kernel, s.hauer, festevam, shawnguo, linux-kernel,
linux-arm-kernel, linux-i2c, aisheng.dong
Hello Alexander,
thanks for looking into that!
On Fri, 2023-04-21 at 15:48 +0200, Alexander Stein wrote:
> Unfortuantely this was just hiding another call path from
> lpi2c_imx_xfer to
> clk_bulk_prepare. Here is my kernel log:
Yes, soon after publishing the patch I reproduced your log as well,
that's why I didn't follow up on the original patch, as it indeed
doesn't solve all the LOCKDEP splats with lpi2c involved and I didn't
have time to look into this yet.
> [ 22.264508] ======================================================
> [ 22.270697] WARNING: possible circular locking dependency detected
> [ 22.276893] 6.3.0-rc7-next-20230420+ #6 Not tainted
> [ 22.281782] ------------------------------------------------------
> [ 22.287968] kworker/2:3/93 is trying to acquire lock:
> [ 22.293034] ffff800009d38bf8 (prepare_lock){+.+.}-{3:3}, at:
> clk_prepare_lock+0x48/0x9c
> [ 22.301095]
> [ 22.301095] but task is already holding lock:
> [ 22.306942] ffff0000039ab100 (i2c_register_adapter){+.+.}-{3:3},
> at:
> i2c_adapter_lock_bus+0x20/0x2c
> [ 22.316046]
> [ 22.316046] which lock already depends on the new lock.
> [ 22.316046]
> [ 22.324238]
> [ 22.324238] the existing dependency chain (in reverse order) is:
> [ 22.331727]
> [ 22.331727] -> #2 (i2c_register_adapter){+.+.}-{3:3}:
> [ 22.338295] __lock_acquire+0x370/0x6e8
> [ 22.342674] lock_acquire.part.0+0xcc/0x208
> [ 22.347399] lock_acquire+0x94/0x14c
> [ 22.351509] rt_mutex_lock_nested+0x5c/0x98
> [ 22.356235] i2c_adapter_lock_bus+0x20/0x2c
> [ 22.360961] i2c_transfer+0x80/0x114
> [ 22.365069] regmap_i2c_read+0x5c/0xa0
> [ 22.369362] _regmap_raw_read+0x110/0x2dc
> [ 22.373905] _regmap_bus_read+0x40/0x74
> [ 22.378274] _regmap_read+0x74/0x248
> [ 22.382393] regmap_read+0x48/0x70
> [ 22.386337] pcf85063_probe+0xf0/0x4f4
> [ 22.390640] i2c_device_probe+0x100/0x2d4
> [ 22.395206] call_driver_probe+0x28/0x15c
> [ 22.399750] really_probe+0x180/0x320
> [ 22.403946] __driver_probe_device+0x84/0x144
> [ 22.408837] driver_probe_device+0x38/0x150
> [ 22.413554] __device_attach_driver+0xcc/0x194
> [ 22.418532] bus_for_each_drv+0x80/0xdc
> [ 22.422910] __device_attach+0xa8/0x1f8
> [ 22.426545] systemd-journald[128]: Oldest entry in
> /var/log/journal/
> e4579cc7db6747028247b9b859e132d6/system.joural is older than the
> configured
> file retention duration (1month), suggesting rotation.
> [ 22.427278] device_initial_probe+0x10/0x18
> [ 22.427290] bus_probe_device+0xa4/0xa8
> [ 22.427299] device_add+0x3b0/0x508
> [ 22.427311] device_register+0x1c/0x28
> [ 22.427323] i2c_new_client_device+0x1c8/0x2bc
> [ 22.427333] of_i2c_register_device+0xb4/0xdc
> [ 22.427344] of_i2c_register_devices+0x80/0x154
> [ 22.456329] systemd-journald[128]: /var/log/journal/
> e4579cc7db6747028247b9b859e132d6/system.journal: Journal heaer limits
> reached
> or header out-of-date, rotating.
> [ 22.458176] i2c_register_adapter+0x184/0x4c8
> [ 22.458202] __i2c_add_numbered_adapter+0x5c/0xa4
> [ 22.502097] i2c_add_adapter+0xa0/0xcc
> [ 22.502122] lpi2c_imx_probe+0x23c/0x350
> [ 22.502135] platform_probe+0x64/0xfc
> [ 22.502146] call_driver_probe+0x28/0x15c
> [ 22.502155] really_probe+0x180/0x320
> [ 22.502164] __driver_probe_device+0x84/0x144
> [ 22.502173] driver_probe_device+0x38/0x150
> [ 22.502182] __device_attach_driver+0xcc/0x194
> [ 22.502191] bus_for_each_drv+0x80/0xdc
> [ 22.502204] __device_attach+0xa8/0x1f8
> [ 22.502212] device_initial_probe+0x10/0x18
> [ 22.502222] bus_probe_device+0xa4/0xa8
> [ 22.502230] deferred_probe_work_func+0xa0/0xf0
> [ 22.502239] process_one_work+0x284/0x5b0
> [ 22.502252] worker_thread+0x68/0x39c
> [ 22.502263] kthread+0x104/0x108
> [ 22.502274] ret_from_fork+0x10/0x20
> [ 22.502286]
> [ 22.502286] -> #1 (rtc_pcf85063:594:(&config->regmap)-
> >lock){+.+.}-{3:3}:
> [ 22.502310] __lock_acquire+0x370/0x6e8
> [ 22.502322] lock_acquire.part.0+0xcc/0x208
> [ 22.502332] lock_acquire+0x94/0x14c
> [ 22.502341] __mutex_lock+0x9c/0x838
> [ 22.502353] mutex_lock_nested+0x20/0x28
> [ 22.502364] regmap_lock_mutex+0x10/0x18
> [ 22.502377] regmap_read+0x38/0x70
> [ 22.502389] pcf85063_clkout_recalc_rate+0x2c/0x78
> [ 22.502403] __clk_core_init+0x46c/0x4e0
> [ 22.502417] __clk_register+0x160/0x23c
> [ 22.502429] devm_clk_register+0x58/0xb4
> [ 22.502441] pcf85063_probe+0x238/0x4f4
> [ 22.502451] i2c_device_probe+0x100/0x2d4
> [ 22.502465] call_driver_probe+0x28/0x15c
> [ 22.502473] really_probe+0x180/0x320
> [ 22.502482] __driver_probe_device+0x84/0x144
> [ 22.502491] driver_probe_device+0x38/0x150
> [ 22.502500] __device_attach_driver+0xcc/0x194
> [ 22.502509] bus_for_each_drv+0x80/0xdc
> [ 22.502521] __device_attach+0xa8/0x1f8
> [ 22.502530] device_initial_probe+0x10/0x18
> [ 22.502539] bus_probe_device+0xa4/0xa8
> [ 22.502548] device_add+0x3b0/0x508
> [ 22.502559] device_register+0x1c/0x28
> [ 22.502570] i2c_new_client_device+0x1c8/0x2bc
> [ 22.502580] of_i2c_register_device+0xb4/0xdc
> [ OK ] Started Network Time Synchronization[ 22.502589]
> of_i2c_register_devices+0x80/0x154
> .[ 22.502599] i2c_register_adapter+0x184/0x4c8
>
> [ 22.502607] __i2c_add_numbered_adapter+0x5c/0xa4
> [ 22.502616] i2c_add_adapter+0xa0/0xcc
> [ 22.502624] lpi2c_imx_probe+0x23c/0x350
> [ 22.502636] platform_probe+0x64/0xfc
> [ 22.502646] call_driver_probe+0x28/0x15c
> [ 22.502655] really_probe+0x180/0x320
> [ 22.502663] __driver_probe_device+0x84/0x144
> [ 22.502672] driver_probe_device+0x38/0x150
> [ 22.502681] __device_attach_driver+0xcc/0x194
> [ 22.502690] bus_for_each_drv+0x80/0xdc
> [ 22.502702] __device_attach+0xa8/0x1f8
> [ 22.502711] device_initial_probe+0x10/0x18
> [ 22.502720] bus_probe_device+0xa4/0xa8
> [ 22.502729] deferred_probe_work_func+0xa0/0xf0
> [ 22.502738] process_one_work+0x284/0x5b0
> [ 22.502749] worker_thread+0x68/0x39c
> [ 22.502760] kthread+0x104/0x108
> [ 22.502770] ret_from_fork+0x10/0x20
> [ 22.502779]
> [ 22.502779] -> #0 (prepare_lock){+.+.}-{3:3}:
> [ 22.502799] check_prev_add+0xb0/0xc80
> [ 22.502809] validate_chain+0x444/0x510
> [ 22.502818] __lock_acquire+0x370/0x6e8
> [ 22.502827] lock_acquire.part.0+0xcc/0x208
> [ 22.502837] lock_acquire+0x94/0x14c
> [ 22.502846] __mutex_lock+0x9c/0x838
> [ 22.502857] mutex_lock_nested+0x20/0x28
> [ 22.502867] clk_prepare_lock+0x48/0x9c
> [ 22.502878] clk_prepare+0x1c/0x3c
> [ 22.502890] clk_bulk_prepare+0x48/0xcc
> [ 22.502899] lpi2c_runtime_resume+0x30/0x84
> [ 22.502910] pm_generic_runtime_resume+0x28/0x3c
> [ 22.502923] __genpd_runtime_resume+0x2c/0xa0
> [ 22.502935] genpd_runtime_resume+0xbc/0x308
> [ 22.502944] __rpm_callback+0x44/0x19c
> [ 22.502953] rpm_callback+0x64/0x70
> [ 22.502962] rpm_resume+0x438/0x6d8
> [ 22.502970] __pm_runtime_resume+0x54/0xb0
> [ 22.502978] lpi2c_imx_master_enable+0x24/0x128
> [ 22.502989] lpi2c_imx_xfer+0x2c/0x3c8
> [ 22.502999] __i2c_transfer+0xe4/0x5a0
> [ 22.503008] i2c_transfer+0x90/0x114
> [ 22.503016] i2c_transfer_buffer_flags+0x58/0x84
> [ 22.503025] regmap_i2c_write+0x1c/0x4c
> [ 22.503035] _regmap_raw_write_impl+0x7dc/0x944
> [ 22.503044] _regmap_bus_raw_write+0x5c/0x74
> [ 22.503052] _regmap_write+0x64/0x238
> [ 22.503060] _regmap_update_bits+0x100/0x11c
> [ 22.503069] regmap_update_bits_base+0x60/0x90
> [ 22.503077] pca953x_gpio_set_value+0x74/0x90
> [ 22.503088] gpiod_set_raw_value_commit+0x6c/0x7c
> [ 22.503098] gpiod_set_value_nocheck+0x68/0x70
> [ 22.503107] gpiod_set_value_cansleep+0x3c/0xa8
> [ 22.503116] gpio_led_set_blocking+0x54/0x7c
> [ 22.503128] set_brightness_delayed+0x90/0xd8
> [ 22.503138] process_one_work+0x284/0x5b0
> [ 22.503149] worker_thread+0x68/0x39c
> [ 22.503160] kthread+0x104/0x108
> [ 22.503169] ret_from_fork+0x10/0x20
> [ 22.503179]
> [ 22.503179] other info that might help us debug this:
> [ 22.503179]
> [ 22.503183] Chain exists of:
> [ 22.503183] prepare_lock --> rtc_pcf85063:594:(&config->regmap)-
> >lock -->
> i2c_register_adapter
> [ 22.503183]
> [ 22.503207] Possible unsafe locking scenario:
> [ 22.503207]
> [ 22.503210] CPU0 CPU1
> [ 22.503213] ---- ----
> [ 22.503216] lock(i2c_register_adapter);
> [ 22.503225]
> lock(rtc_pcf85063:594:(&config-
> > regmap)->lock);
> [ 22.503235]
> lock(i2c_register_adapter);
> [ 22.503244] lock(prepare_lock);
> [ 22.503253]
> [ 22.503253] *** DEADLOCK ***
>
> Now lpi2c_runtime_resume will call into clk_prepare() which also
> calls
> clk_prepare_lock() (identical to clk_get_rate).
--
Alexander Sverdlin
Siemens AG
www.siemens.com
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-04-21 13:59 ` Marc Kleine-Budde
@ 2023-04-24 7:03 ` Alexander Stein
2023-04-30 7:05 ` Wolfram Sang
0 siblings, 1 reply; 14+ messages in thread
From: Alexander Stein @ 2023-04-24 7:03 UTC (permalink / raw)
To: Marc Kleine-Budde
Cc: NXP Linux Team, A. Sverdlin, Dong Aisheng, Shawn Guo,
Sascha Hauer, Pengutronix Kernel Team, Fabio Estevam, linux-i2c,
linux-arm-kernel, linux-kernel
Hi Marc,
Am Freitag, 21. April 2023, 15:59:52 CEST schrieb Marc Kleine-Budde:
> * PGP Signed by an unknown key
>
> On 21.04.2023 15:48:59, Alexander Stein wrote:
> [...]
>
> > Now lpi2c_runtime_resume will call into clk_prepare() which also calls
> > clk_prepare_lock() (identical to clk_get_rate).
>
> IIRC this is a general problem^w limitation of the clock framework,
> clock providers cannot use clocks themselves in certain callback, e.g.
> set_rate.
Well, that's essentially impossible when this clock provider is attached via
i2c. i2c transfers potentially need to change or prepare clocks.
One problem is that during clock registration (__clk_core_init) in the call to
clk_ops.recalc_rate an i2c transfer is issued (via regmap). This is the
inverse lock order to a regular transfer runtime resuming the i2c master and
preparing the clocks.
While looking at this, is_prepared is also affected by this. It's reading a
register, thus issuing a i2c transfer. But this function can also be called
from within clk_unprepare_unused_subtree, which holds clk_prepare_lock as
well.
This might be avoided by using regcache, but I'm not really sure this catches
every case.
Best regards,
Alexander
--
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
http://www.tq-group.com/
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-03-10 13:08 [PATCH v3] i2c: lpi2c: cache peripheral clock rate A. Sverdlin
2023-04-21 13:48 ` Alexander Stein
@ 2023-04-24 8:08 ` Alexander Stein
1 sibling, 0 replies; 14+ messages in thread
From: Alexander Stein @ 2023-04-24 8:08 UTC (permalink / raw)
To: NXP Linux Team, A. Sverdlin
Cc: Alexander Sverdlin, Dong Aisheng, Shawn Guo, Sascha Hauer,
Pengutronix Kernel Team, Fabio Estevam, linux-i2c,
linux-arm-kernel, linux-kernel
Am Freitag, 10. März 2023, 14:08:15 CEST schrieb A. Sverdlin:
> From: Alexander Sverdlin <alexander.sverdlin@siemens.com>
>
> One of the reasons to do it is to save some CPU cycles on cpu_freq_get()
> under mutex. The second reason if the (false-positive) lockdep splat caused
> by the recursive feature of the "prepare_lock" (one clock instance is I2C
> peripheral clock and another is pcf85063 RTC as clock provider):
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.15.71+... #1 Tainted: G O
> ------------------------------------------------------
> fs-value/2332 is trying to acquire lock:
> ffff8000096cae08 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock
>
> but task is already holding lock:
> ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus
>
> which lock already depends on the new lock.
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (i2c_register_adapter){+.+.}-{3:3}:
> lock_acquire
> rt_mutex_lock_nested
> i2c_adapter_lock_bus
> i2c_transfer
> regmap_i2c_read
> _regmap_raw_read
> _regmap_bus_read
> _regmap_read
> regmap_read
> pcf85063_probe
> i2c_device_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> device_add
> device_register
> i2c_new_client_device
> of_i2c_register_devices
> i2c_register_adapter
> __i2c_add_numbered_adapter
> i2c_add_adapter
> lpi2c_imx_probe
> platform_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> deferred_probe_work_func
> process_one_work
> worker_thread
> kthread
> ret_from_fork
>
> -> #1 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
> lock_acquire
> __mutex_lock
> mutex_lock_nested
> regmap_lock_mutex
> regmap_read
> pcf85063_clkout_recalc_rate
> __clk_register
> devm_clk_register
> pcf85063_probe
> i2c_device_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> device_add
> device_register
> i2c_new_client_device
> of_i2c_register_devices
> i2c_register_adapter
> __i2c_add_numbered_adapter
> i2c_add_adapter
> lpi2c_imx_probe
> platform_probe
> really_probe
> __driver_probe_device
> driver_probe_device
> __device_attach_driver
> bus_for_each_drv
> __device_attach
> device_initial_probe
> bus_probe_device
> deferred_probe_work_func
> process_one_work
> worker_thread
> kthread
> ret_from_fork
>
> -> #0 (prepare_lock){+.+.}-{3:3}:
> __lock_acquire
> lock_acquire.part.0
> lock_acquire
> __mutex_lock
> mutex_lock_nested
> clk_prepare_lock
> clk_get_rate
> lpi2c_imx_xfer
> __i2c_transfer
> i2c_transfer
> regmap_i2c_read
> _regmap_raw_read
> regmap_raw_read
> regmap_bulk_read
> at24_read
> nvmem_reg_read
> bin_attr_nvmem_read
> sysfs_kf_bin_read
> kernfs_fop_read_iter
> new_sync_read
> vfs_read
> ksys_read
> __arm64_sys_read
> invoke_syscall
> ...
>
> other info that might help us debug this:
>
> Chain exists of:
> prepare_lock --> rtc_pcf85063:560:(&config->regmap)->lock -->
> i2c_register_adapter
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(i2c_register_adapter);
>
> lock(rtc_pcf85063:560:(&config->regmap)->lock); lock(i2c_register_adapter);
> lock(prepare_lock);
>
> *** DEADLOCK ***
>
> 4 locks held by .../2332:
> #0: ffff0000146eb288 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_read_iter
> #1: ffff000010fe4400 (kn->active#72){.+.+}-{0:0}, at: kernfs_fop_read_iter
> #2: ffff0000110168e8 (&at24->lock){+.+.}-{3:3}, at: at24_read
> #3: ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus
>
> stack backtrace:
> CPU: 1 PID: 2332 Comm: ... Tainted: G O 5.15.71+... #1
> Hardware name: ... (DT)
> Call trace:
> dump_backtrace
> show_stack
> dump_stack_lvl
> dump_stack
> print_circular_bug
> check_noncircular
> __lock_acquire
> lock_acquire.part.0
> lock_acquire
> __mutex_lock
> mutex_lock_nested
> clk_prepare_lock
> clk_get_rate
> lpi2c_imx_xfer
> __i2c_transfer
> i2c_transfer
> regmap_i2c_read
> _regmap_raw_read
> regmap_raw_read
> regmap_bulk_read
> at24_read
> nvmem_reg_read
> bin_attr_nvmem_read
> sysfs_kf_bin_read
> kernfs_fop_read_iter
> new_sync_read
> vfs_read
> ksys_read
> __arm64_sys_read
> invoke_syscall
> ...
>
> Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Note: [1] needs to be applied as well in order to get rid of all the lockdep
errors.
[1] https://lore.kernel.org/linux-i2c/20230424080627.20564-1-alexander.stein@ew.tq-group.com/T/#u
> ---
> drivers/i2c/busses/i2c-imx-lpi2c.c | 33 +++++++++++++++++++++++++++---
> 1 file changed, 30 insertions(+), 3 deletions(-)
>
> Changelog:
> v3: fixed build error reported by kernel test robot <lkp@intel.com>
>
> https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/
> v2: added clk_notifier as Alexander suggested
>
> diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c
> b/drivers/i2c/busses/i2c-imx-lpi2c.c index 188f2a36d2fd6..5f1d1d4e018bd
> 100644
> --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> @@ -100,6 +100,8 @@ struct lpi2c_imx_struct {
> __u8 *rx_buf;
> __u8 *tx_buf;
> struct completion complete;
> + struct notifier_block clk_change_nb;
> + unsigned int rate_per;
> unsigned int msglen;
> unsigned int delivered;
> unsigned int block_data;
> @@ -198,24 +200,37 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct
> *lpi2c_imx) } while (1);
> }
>
> +static int lpi2c_imx_clk_change_cb(struct notifier_block *nb,
> + unsigned long action, void *data)
> +{
> + struct clk_notifier_data *ndata = data;
> + struct lpi2c_imx_struct *lpi2c_imx = container_of(nb,
> + struct
lpi2c_imx_struct,
> +
clk_change_nb);
> +
> + if (action & POST_RATE_CHANGE)
> + lpi2c_imx->rate_per = ndata->new_rate;
> +
> + return NOTIFY_OK;
> +}
> +
> /* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
> static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
> {
> u8 prescale, filt, sethold, clkhi, clklo, datavd;
> - unsigned int clk_rate, clk_cycle;
> + unsigned int clk_cycle;
> enum lpi2c_imx_pincfg pincfg;
> unsigned int temp;
>
> lpi2c_imx_set_mode(lpi2c_imx);
>
> - clk_rate = clk_get_rate(lpi2c_imx->clks[0].clk);
> if (lpi2c_imx->mode == HS || lpi2c_imx->mode == ULTRA_FAST)
> filt = 0;
> else
> filt = 2;
>
> for (prescale = 0; prescale <= 7; prescale++) {
> - clk_cycle = clk_rate / ((1 << prescale) * lpi2c_imx-
>bitrate)
> + clk_cycle = lpi2c_imx->rate_per / ((1 << prescale) *
lpi2c_imx->bitrate)
> - 3 - (filt >> 1);
> clkhi = (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1);
> clklo = clk_cycle - clkhi;
> @@ -588,6 +603,18 @@ static int lpi2c_imx_probe(struct platform_device
> *pdev) if (ret)
> return ret;
>
> + lpi2c_imx->clk_change_nb.notifier_call = lpi2c_imx_clk_change_cb;
> + ret = devm_clk_notifier_register(&pdev->dev, lpi2c_imx->clks[0].clk,
> + &lpi2c_imx->clk_change_nb);
> + if (ret)
> + return dev_err_probe(&pdev->dev, ret,
> + "can't register peripheral clock
notifier\n");
> + lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk);
> + if (!lpi2c_imx->rate_per) {
> + dev_err(&pdev->dev, "can't get I2C peripheral clock
rate\n");
> + return -EINVAL;
> + }
> +
> pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> pm_runtime_use_autosuspend(&pdev->dev);
> pm_runtime_get_noresume(&pdev->dev);
--
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
http://www.tq-group.com/
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-04-24 7:03 ` Alexander Stein
@ 2023-04-30 7:05 ` Wolfram Sang
2023-05-02 6:50 ` Alexander Stein
0 siblings, 1 reply; 14+ messages in thread
From: Wolfram Sang @ 2023-04-30 7:05 UTC (permalink / raw)
To: Alexander Stein
Cc: Marc Kleine-Budde, NXP Linux Team, A. Sverdlin, Dong Aisheng,
Shawn Guo, Sascha Hauer, Pengutronix Kernel Team, Fabio Estevam,
linux-i2c, linux-arm-kernel, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 540 bytes --]
> > IIRC this is a general problem^w limitation of the clock framework,
> > clock providers cannot use clocks themselves in certain callback, e.g.
> > set_rate.
>
> Well, that's essentially impossible when this clock provider is attached via
> i2c. i2c transfers potentially need to change or prepare clocks.
So, as I get it, this is not a specific lpi2c problem but affecting any
I2C controller driver which uses get_rate() to setup a transfer to a
remote I2C clock provider? And this lockdep warning is a false-positive?
[-- Attachment #2: signature.asc --]
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^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-04-30 7:05 ` Wolfram Sang
@ 2023-05-02 6:50 ` Alexander Stein
2023-05-02 7:03 ` Marc Kleine-Budde
0 siblings, 1 reply; 14+ messages in thread
From: Alexander Stein @ 2023-05-02 6:50 UTC (permalink / raw)
To: Wolfram Sang, Alexander Stein, Marc Kleine-Budde, NXP Linux Team,
A. Sverdlin, Dong Aisheng, Shawn Guo, Sascha Hauer,
Pengutronix Kernel Team, Fabio Estevam, linux-i2c,
linux-arm-kernel, linux-kernel
Hello Wolfgang,
Am Sonntag, 30. April 2023, 09:05:55 CEST schrieb Wolfram Sang:
> * PGP Signed by an unknown key
>
> > > IIRC this is a general problem^w limitation of the clock framework,
> > > clock providers cannot use clocks themselves in certain callback, e.g.
> > > set_rate.
> >
> > Well, that's essentially impossible when this clock provider is attached
> > via i2c. i2c transfers potentially need to change or prepare clocks.
>
> So, as I get it, this is not a specific lpi2c problem but affecting any
> I2C controller driver which uses get_rate() to setup a transfer to a
> remote I2C clock provider? And this lockdep warning is a false-positive?
Yes, IMHO this could potentially occur on every I2C controller driver, if a
clock provider while holding the clk_prepare_lock, e.g. during registration,
issues an i2c transfer.
I'm not so sure if this is a false-positive, but more like trying to do a
nested lock.
Best regards
Alexander
--
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
http://www.tq-group.com/
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-05-02 6:50 ` Alexander Stein
@ 2023-05-02 7:03 ` Marc Kleine-Budde
0 siblings, 0 replies; 14+ messages in thread
From: Marc Kleine-Budde @ 2023-05-02 7:03 UTC (permalink / raw)
To: Alexander Stein
Cc: Wolfram Sang, NXP Linux Team, A. Sverdlin, Dong Aisheng,
Shawn Guo, Sascha Hauer, Pengutronix Kernel Team, Fabio Estevam,
linux-i2c, linux-arm-kernel, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 1828 bytes --]
On 02.05.2023 08:50:06, Alexander Stein wrote:
> Hello Wolfgang,
>
> Am Sonntag, 30. April 2023, 09:05:55 CEST schrieb Wolfram Sang:
> > * PGP Signed by an unknown key
> >
> > > > IIRC this is a general problem^w limitation of the clock framework,
> > > > clock providers cannot use clocks themselves in certain callback, e.g.
> > > > set_rate.
> > >
> > > Well, that's essentially impossible when this clock provider is attached
> > > via i2c. i2c transfers potentially need to change or prepare clocks.
> >
> > So, as I get it, this is not a specific lpi2c problem but affecting any
> > I2C controller driver which uses get_rate() to setup a transfer to a
> > remote I2C clock provider? And this lockdep warning is a false-positive?
>
> Yes, IMHO this could potentially occur on every I2C controller driver, if a
> clock provider while holding the clk_prepare_lock, e.g. during registration,
> issues an i2c transfer.
> I'm not so sure if this is a false-positive, but more like trying to do a
> nested lock.
It's a general limitation of the clock framework. The clk_prepare_lock()
is taken by clk_prepare() and by clk_get_rate(). So if you implement a
clock provider driver that uses I2C, which might use clk_get_rate() it
might deadlock. However there's a workaround for nested I2C calls:
533ddeb1e86f "(clk: allow reentrant calls into the clk framework,
2013-03-28)". This doesn't work for SPI, as it's using a worker thread.
| https://elixir.bootlin.com/linux/v6.3/source/drivers/clk/clk.c#L128
regards,
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung Nürnberg | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-04-21 13:48 ` Alexander Stein
2023-04-21 13:59 ` Marc Kleine-Budde
2023-04-21 14:10 ` Sverdlin, Alexander
@ 2023-05-15 9:11 ` Alexander Stein
2023-05-15 12:04 ` Sverdlin, Alexander
2023-05-15 13:11 ` Sverdlin, Alexander
3 siblings, 1 reply; 14+ messages in thread
From: Alexander Stein @ 2023-05-15 9:11 UTC (permalink / raw)
To: A. Sverdlin
Cc: NXP Linux Team, Alexander Sverdlin, Dong Aisheng, Shawn Guo,
Sascha Hauer, Pengutronix Kernel Team, Fabio Estevam, linux-i2c,
linux-arm-kernel, linux-kernel
Hi,
Am Freitag, 21. April 2023, 15:48:59 CEST schrieb Alexander Stein:
> Hi,
>
> sorry for the delay.
>
> Am Freitag, 10. März 2023, 14:08:15 CEST schrieb A. Sverdlin:
> > From: Alexander Sverdlin <alexander.sverdlin@siemens.com>
> >
> > One of the reasons to do it is to save some CPU cycles on cpu_freq_get()
> > under mutex. The second reason if the (false-positive) lockdep splat
> > caused
> > by the recursive feature of the "prepare_lock" (one clock instance is I2C
> > peripheral clock and another is pcf85063 RTC as clock provider):
> >
> > ======================================================
> > WARNING: possible circular locking dependency detected
> > 5.15.71+... #1 Tainted: G O
> > ------------------------------------------------------
> > fs-value/2332 is trying to acquire lock:
> > ffff8000096cae08 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock
> >
> > but task is already holding lock:
> > ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at:
> > i2c_adapter_lock_bus
> >
> > which lock already depends on the new lock.
> >
> > the existing dependency chain (in reverse order) is:
> >
> > -> #2 (i2c_register_adapter){+.+.}-{3:3}:
> > lock_acquire
> > rt_mutex_lock_nested
> > i2c_adapter_lock_bus
> > i2c_transfer
> > regmap_i2c_read
> > _regmap_raw_read
> > _regmap_bus_read
> > _regmap_read
> > regmap_read
> > pcf85063_probe
> > i2c_device_probe
> > really_probe
> > __driver_probe_device
> > driver_probe_device
> > __device_attach_driver
> > bus_for_each_drv
> > __device_attach
> > device_initial_probe
> > bus_probe_device
> > device_add
> > device_register
> > i2c_new_client_device
> > of_i2c_register_devices
> > i2c_register_adapter
> > __i2c_add_numbered_adapter
> > i2c_add_adapter
> > lpi2c_imx_probe
> > platform_probe
> > really_probe
> > __driver_probe_device
> > driver_probe_device
> > __device_attach_driver
> > bus_for_each_drv
> > __device_attach
> > device_initial_probe
> > bus_probe_device
> > deferred_probe_work_func
> > process_one_work
> > worker_thread
> > kthread
> > ret_from_fork
> >
> > -> #1 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
> > lock_acquire
> > __mutex_lock
> > mutex_lock_nested
> > regmap_lock_mutex
> > regmap_read
> > pcf85063_clkout_recalc_rate
> > __clk_register
> > devm_clk_register
> > pcf85063_probe
> > i2c_device_probe
> > really_probe
> > __driver_probe_device
> > driver_probe_device
> > __device_attach_driver
> > bus_for_each_drv
> > __device_attach
> > device_initial_probe
> > bus_probe_device
> > device_add
> > device_register
> > i2c_new_client_device
> > of_i2c_register_devices
> > i2c_register_adapter
> > __i2c_add_numbered_adapter
> > i2c_add_adapter
> > lpi2c_imx_probe
> > platform_probe
> > really_probe
> > __driver_probe_device
> > driver_probe_device
> > __device_attach_driver
> > bus_for_each_drv
> > __device_attach
> > device_initial_probe
> > bus_probe_device
> > deferred_probe_work_func
> > process_one_work
> > worker_thread
> > kthread
> > ret_from_fork
> >
> > -> #0 (prepare_lock){+.+.}-{3:3}:
> > __lock_acquire
> > lock_acquire.part.0
> > lock_acquire
> > __mutex_lock
> > mutex_lock_nested
> > clk_prepare_lock
> > clk_get_rate
> > lpi2c_imx_xfer
> > __i2c_transfer
> > i2c_transfer
> > regmap_i2c_read
> > _regmap_raw_read
> > regmap_raw_read
> > regmap_bulk_read
> > at24_read
> > nvmem_reg_read
> > bin_attr_nvmem_read
> > sysfs_kf_bin_read
> > kernfs_fop_read_iter
> > new_sync_read
> > vfs_read
> > ksys_read
> > __arm64_sys_read
> > invoke_syscall
> > ...
> >
> > other info that might help us debug this:
> >
> > Chain exists of:
> > prepare_lock --> rtc_pcf85063:560:(&config->regmap)->lock -->
> >
> > i2c_register_adapter
> >
> > Possible unsafe locking scenario:
> > CPU0 CPU1
> > ---- ----
> >
> > lock(i2c_register_adapter);
> >
> > lock(rtc_pcf85063:560:(&config->regmap)->lock);
> > lock(i2c_register_adapter);
> >
> > lock(prepare_lock);
> >
> > *** DEADLOCK ***
> >
> > 4 locks held by .../2332:
> > #0: ffff0000146eb288 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_read_iter
> > #1: ffff000010fe4400 (kn->active#72){.+.+}-{0:0}, at:
> > kernfs_fop_read_iter
> > #2: ffff0000110168e8 (&at24->lock){+.+.}-{3:3}, at: at24_read
> >
> > #3: ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at:
> > i2c_adapter_lock_bus
> >
> > stack backtrace:
> > CPU: 1 PID: 2332 Comm: ... Tainted: G O 5.15.71+... #1
> > Hardware name: ... (DT)
> >
> > Call trace:
> > dump_backtrace
> > show_stack
> > dump_stack_lvl
> > dump_stack
> > print_circular_bug
> > check_noncircular
> > __lock_acquire
> > lock_acquire.part.0
> > lock_acquire
> > __mutex_lock
> > mutex_lock_nested
> > clk_prepare_lock
> > clk_get_rate
> > lpi2c_imx_xfer
> > __i2c_transfer
> > i2c_transfer
> > regmap_i2c_read
> > _regmap_raw_read
> > regmap_raw_read
> > regmap_bulk_read
> > at24_read
> > nvmem_reg_read
> > bin_attr_nvmem_read
> > sysfs_kf_bin_read
> > kernfs_fop_read_iter
> > new_sync_read
> > vfs_read
> > ksys_read
> > __arm64_sys_read
> > invoke_syscall
> > ...
> >
> > Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
> > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
> > ---
> >
> > drivers/i2c/busses/i2c-imx-lpi2c.c | 33 +++++++++++++++++++++++++++---
> > 1 file changed, 30 insertions(+), 3 deletions(-)
> >
> > Changelog:
> > v3: fixed build error reported by kernel test robot <lkp@intel.com>
> >
> > https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/
> > v2: added clk_notifier as Alexander suggested
> >
> > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > b/drivers/i2c/busses/i2c-imx-lpi2c.c index 188f2a36d2fd6..5f1d1d4e018bd
> > 100644
> > --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > @@ -100,6 +100,8 @@ struct lpi2c_imx_struct {
> >
> > __u8 *rx_buf;
> > __u8 *tx_buf;
> > struct completion complete;
> >
> > + struct notifier_block clk_change_nb;
> > + unsigned int rate_per;
> >
> > unsigned int msglen;
> > unsigned int delivered;
> > unsigned int block_data;
> >
> > @@ -198,24 +200,37 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct
> > *lpi2c_imx) } while (1);
> >
> > }
> >
> > +static int lpi2c_imx_clk_change_cb(struct notifier_block *nb,
> > + unsigned long action, void *data)
> > +{
> > + struct clk_notifier_data *ndata = data;
> > + struct lpi2c_imx_struct *lpi2c_imx = container_of(nb,
> > + struct
>
> lpi2c_imx_struct,
>
> > +
>
> clk_change_nb);
>
> > +
> > + if (action & POST_RATE_CHANGE)
> > + lpi2c_imx->rate_per = ndata->new_rate;
> > +
> > + return NOTIFY_OK;
> > +}
> > +
> >
> > /* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
> > static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
> > {
> >
> > u8 prescale, filt, sethold, clkhi, clklo, datavd;
> >
> > - unsigned int clk_rate, clk_cycle;
> > + unsigned int clk_cycle;
> >
> > enum lpi2c_imx_pincfg pincfg;
> > unsigned int temp;
> >
> > lpi2c_imx_set_mode(lpi2c_imx);
> >
> > - clk_rate = clk_get_rate(lpi2c_imx->clks[0].clk);
> >
> > if (lpi2c_imx->mode == HS || lpi2c_imx->mode == ULTRA_FAST)
> >
> > filt = 0;
> >
> > else
> >
> > filt = 2;
> >
> > for (prescale = 0; prescale <= 7; prescale++) {
> >
> > - clk_cycle = clk_rate / ((1 << prescale) * lpi2c_imx-
> >
> >bitrate)
> >
> > + clk_cycle = lpi2c_imx->rate_per / ((1 << prescale) *
>
> lpi2c_imx->bitrate)
>
> > - 3 - (filt >> 1);
> >
> > clkhi = (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1);
> > clklo = clk_cycle - clkhi;
> >
> > @@ -588,6 +603,18 @@ static int lpi2c_imx_probe(struct platform_device
> > *pdev) if (ret)
> >
> > return ret;
> >
> > + lpi2c_imx->clk_change_nb.notifier_call = lpi2c_imx_clk_change_cb;
> > + ret = devm_clk_notifier_register(&pdev->dev, lpi2c_imx->clks[0].clk,
> > + &lpi2c_imx->clk_change_nb);
> > + if (ret)
> > + return dev_err_probe(&pdev->dev, ret,
> > + "can't register peripheral clock
>
> notifier\n");
>
> > + lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk);
> > + if (!lpi2c_imx->rate_per) {
> > + dev_err(&pdev->dev, "can't get I2C peripheral clock
>
> rate\n");
>
> > + return -EINVAL;
> > + }
> > +
>
> I would switch the order of the calls to devm_clk_notifier_register() and
> clk_get_rate(). AFAICS this looks like a possible lost update. The notifier
> might change rate_per before the (old) value from clk_get_rate is actually
> assigned.
>
> With this change you fix the following call chain (from a kernel log)
>
> [ 4.562396] clk_prepare_lock+0x48/0x9c
> [ 4.566740] clk_get_rate+0x1c/0x74
> [ 4.570736] lpi2c_imx_config+0x4c/0x190
> [ 4.575167] lpi2c_imx_master_enable+0x54/0x128
> [ 4.580205] lpi2c_imx_xfer+0x2c/0x3c8
>
> Unfortuantely this was just hiding another call path from lpi2c_imx_xfer to
> clk_bulk_prepare. Here is my kernel log:
>
> [ 22.264508] ======================================================
> [ 22.270697] WARNING: possible circular locking dependency detected
> [ 22.276893] 6.3.0-rc7-next-20230420+ #6 Not tainted
> [ 22.281782] ------------------------------------------------------
> [ 22.287968] kworker/2:3/93 is trying to acquire lock:
> [ 22.293034] ffff800009d38bf8 (prepare_lock){+.+.}-{3:3}, at:
> clk_prepare_lock+0x48/0x9c
> [ 22.301095]
> [ 22.301095] but task is already holding lock:
> [ 22.306942] ffff0000039ab100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus+0x20/0x2c
> [ 22.316046]
> [ 22.316046] which lock already depends on the new lock.
> [ 22.316046]
> [ 22.324238]
> [ 22.324238] the existing dependency chain (in reverse order) is:
> [ 22.331727]
> [ 22.331727] -> #2 (i2c_register_adapter){+.+.}-{3:3}:
> [ 22.338295] __lock_acquire+0x370/0x6e8
> [ 22.342674] lock_acquire.part.0+0xcc/0x208
> [ 22.347399] lock_acquire+0x94/0x14c
> [ 22.351509] rt_mutex_lock_nested+0x5c/0x98
> [ 22.356235] i2c_adapter_lock_bus+0x20/0x2c
> [ 22.360961] i2c_transfer+0x80/0x114
> [ 22.365069] regmap_i2c_read+0x5c/0xa0
> [ 22.369362] _regmap_raw_read+0x110/0x2dc
> [ 22.373905] _regmap_bus_read+0x40/0x74
> [ 22.378274] _regmap_read+0x74/0x248
> [ 22.382393] regmap_read+0x48/0x70
> [ 22.386337] pcf85063_probe+0xf0/0x4f4
> [ 22.390640] i2c_device_probe+0x100/0x2d4
> [ 22.395206] call_driver_probe+0x28/0x15c
> [ 22.399750] really_probe+0x180/0x320
> [ 22.403946] __driver_probe_device+0x84/0x144
> [ 22.408837] driver_probe_device+0x38/0x150
> [ 22.413554] __device_attach_driver+0xcc/0x194
> [ 22.418532] bus_for_each_drv+0x80/0xdc
> [ 22.422910] __device_attach+0xa8/0x1f8
> [ 22.426545] systemd-journald[128]: Oldest entry in /var/log/journal/
> e4579cc7db6747028247b9b859e132d6/system.joural is older than the configured
> file retention duration (1month), suggesting rotation.
> [ 22.427278] device_initial_probe+0x10/0x18
> [ 22.427290] bus_probe_device+0xa4/0xa8
> [ 22.427299] device_add+0x3b0/0x508
> [ 22.427311] device_register+0x1c/0x28
> [ 22.427323] i2c_new_client_device+0x1c8/0x2bc
> [ 22.427333] of_i2c_register_device+0xb4/0xdc
> [ 22.427344] of_i2c_register_devices+0x80/0x154
> [ 22.456329] systemd-journald[128]: /var/log/journal/
> e4579cc7db6747028247b9b859e132d6/system.journal: Journal heaer limits
> reached or header out-of-date, rotating.
> [ 22.458176] i2c_register_adapter+0x184/0x4c8
> [ 22.458202] __i2c_add_numbered_adapter+0x5c/0xa4
> [ 22.502097] i2c_add_adapter+0xa0/0xcc
> [ 22.502122] lpi2c_imx_probe+0x23c/0x350
> [ 22.502135] platform_probe+0x64/0xfc
> [ 22.502146] call_driver_probe+0x28/0x15c
> [ 22.502155] really_probe+0x180/0x320
> [ 22.502164] __driver_probe_device+0x84/0x144
> [ 22.502173] driver_probe_device+0x38/0x150
> [ 22.502182] __device_attach_driver+0xcc/0x194
> [ 22.502191] bus_for_each_drv+0x80/0xdc
> [ 22.502204] __device_attach+0xa8/0x1f8
> [ 22.502212] device_initial_probe+0x10/0x18
> [ 22.502222] bus_probe_device+0xa4/0xa8
> [ 22.502230] deferred_probe_work_func+0xa0/0xf0
> [ 22.502239] process_one_work+0x284/0x5b0
> [ 22.502252] worker_thread+0x68/0x39c
> [ 22.502263] kthread+0x104/0x108
> [ 22.502274] ret_from_fork+0x10/0x20
> [ 22.502286]
> [ 22.502286] -> #1 (rtc_pcf85063:594:(&config->regmap)->lock){+.+.}-{3:3}:
> [ 22.502310] __lock_acquire+0x370/0x6e8
> [ 22.502322] lock_acquire.part.0+0xcc/0x208
> [ 22.502332] lock_acquire+0x94/0x14c
> [ 22.502341] __mutex_lock+0x9c/0x838
> [ 22.502353] mutex_lock_nested+0x20/0x28
> [ 22.502364] regmap_lock_mutex+0x10/0x18
> [ 22.502377] regmap_read+0x38/0x70
> [ 22.502389] pcf85063_clkout_recalc_rate+0x2c/0x78
> [ 22.502403] __clk_core_init+0x46c/0x4e0
> [ 22.502417] __clk_register+0x160/0x23c
> [ 22.502429] devm_clk_register+0x58/0xb4
> [ 22.502441] pcf85063_probe+0x238/0x4f4
> [ 22.502451] i2c_device_probe+0x100/0x2d4
> [ 22.502465] call_driver_probe+0x28/0x15c
> [ 22.502473] really_probe+0x180/0x320
> [ 22.502482] __driver_probe_device+0x84/0x144
> [ 22.502491] driver_probe_device+0x38/0x150
> [ 22.502500] __device_attach_driver+0xcc/0x194
> [ 22.502509] bus_for_each_drv+0x80/0xdc
> [ 22.502521] __device_attach+0xa8/0x1f8
> [ 22.502530] device_initial_probe+0x10/0x18
> [ 22.502539] bus_probe_device+0xa4/0xa8
> [ 22.502548] device_add+0x3b0/0x508
> [ 22.502559] device_register+0x1c/0x28
> [ 22.502570] i2c_new_client_device+0x1c8/0x2bc
> [ 22.502580] of_i2c_register_device+0xb4/0xdc
> [ OK ] Started Network Time Synchronization[ 22.502589]
> of_i2c_register_devices+0x80/0x154
> .[ 22.502599] i2c_register_adapter+0x184/0x4c8
>
> [ 22.502607] __i2c_add_numbered_adapter+0x5c/0xa4
> [ 22.502616] i2c_add_adapter+0xa0/0xcc
> [ 22.502624] lpi2c_imx_probe+0x23c/0x350
> [ 22.502636] platform_probe+0x64/0xfc
> [ 22.502646] call_driver_probe+0x28/0x15c
> [ 22.502655] really_probe+0x180/0x320
> [ 22.502663] __driver_probe_device+0x84/0x144
> [ 22.502672] driver_probe_device+0x38/0x150
> [ 22.502681] __device_attach_driver+0xcc/0x194
> [ 22.502690] bus_for_each_drv+0x80/0xdc
> [ 22.502702] __device_attach+0xa8/0x1f8
> [ 22.502711] device_initial_probe+0x10/0x18
> [ 22.502720] bus_probe_device+0xa4/0xa8
> [ 22.502729] deferred_probe_work_func+0xa0/0xf0
> [ 22.502738] process_one_work+0x284/0x5b0
> [ 22.502749] worker_thread+0x68/0x39c
> [ 22.502760] kthread+0x104/0x108
> [ 22.502770] ret_from_fork+0x10/0x20
> [ 22.502779]
> [ 22.502779] -> #0 (prepare_lock){+.+.}-{3:3}:
> [ 22.502799] check_prev_add+0xb0/0xc80
> [ 22.502809] validate_chain+0x444/0x510
> [ 22.502818] __lock_acquire+0x370/0x6e8
> [ 22.502827] lock_acquire.part.0+0xcc/0x208
> [ 22.502837] lock_acquire+0x94/0x14c
> [ 22.502846] __mutex_lock+0x9c/0x838
> [ 22.502857] mutex_lock_nested+0x20/0x28
> [ 22.502867] clk_prepare_lock+0x48/0x9c
> [ 22.502878] clk_prepare+0x1c/0x3c
> [ 22.502890] clk_bulk_prepare+0x48/0xcc
> [ 22.502899] lpi2c_runtime_resume+0x30/0x84
> [ 22.502910] pm_generic_runtime_resume+0x28/0x3c
> [ 22.502923] __genpd_runtime_resume+0x2c/0xa0
> [ 22.502935] genpd_runtime_resume+0xbc/0x308
> [ 22.502944] __rpm_callback+0x44/0x19c
> [ 22.502953] rpm_callback+0x64/0x70
> [ 22.502962] rpm_resume+0x438/0x6d8
> [ 22.502970] __pm_runtime_resume+0x54/0xb0
> [ 22.502978] lpi2c_imx_master_enable+0x24/0x128
> [ 22.502989] lpi2c_imx_xfer+0x2c/0x3c8
> [ 22.502999] __i2c_transfer+0xe4/0x5a0
> [ 22.503008] i2c_transfer+0x90/0x114
> [ 22.503016] i2c_transfer_buffer_flags+0x58/0x84
> [ 22.503025] regmap_i2c_write+0x1c/0x4c
> [ 22.503035] _regmap_raw_write_impl+0x7dc/0x944
> [ 22.503044] _regmap_bus_raw_write+0x5c/0x74
> [ 22.503052] _regmap_write+0x64/0x238
> [ 22.503060] _regmap_update_bits+0x100/0x11c
> [ 22.503069] regmap_update_bits_base+0x60/0x90
> [ 22.503077] pca953x_gpio_set_value+0x74/0x90
> [ 22.503088] gpiod_set_raw_value_commit+0x6c/0x7c
> [ 22.503098] gpiod_set_value_nocheck+0x68/0x70
> [ 22.503107] gpiod_set_value_cansleep+0x3c/0xa8
> [ 22.503116] gpio_led_set_blocking+0x54/0x7c
> [ 22.503128] set_brightness_delayed+0x90/0xd8
> [ 22.503138] process_one_work+0x284/0x5b0
> [ 22.503149] worker_thread+0x68/0x39c
> [ 22.503160] kthread+0x104/0x108
> [ 22.503169] ret_from_fork+0x10/0x20
> [ 22.503179]
> [ 22.503179] other info that might help us debug this:
> [ 22.503179]
> [ 22.503183] Chain exists of:
> [ 22.503183] prepare_lock --> rtc_pcf85063:594:(&config->regmap)->lock
> --> i2c_register_adapter
> [ 22.503183]
> [ 22.503207] Possible unsafe locking scenario:
> [ 22.503207]
> [ 22.503210] CPU0 CPU1
> [ 22.503213] ---- ----
> [ 22.503216] lock(i2c_register_adapter);
> [ 22.503225]
> lock(rtc_pcf85063:594:(&config-
> >regmap)->lock);
>
> [ 22.503235] lock(i2c_register_adapter);
> [ 22.503244] lock(prepare_lock);
> [ 22.503253]
> [ 22.503253] *** DEADLOCK ***
>
> Now lpi2c_runtime_resume will call into clk_prepare() which also calls
> clk_prepare_lock() (identical to clk_get_rate).
>
> Best regards,
> Alexader
>
> > pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> > pm_runtime_use_autosuspend(&pdev->dev);
> > pm_runtime_get_noresume(&pdev->dev);
With commit fa39065833db ("i2c: imx-lpi2c: avoid taking clk_prepare mutex in
PM callbacks") in place, the additional deadlock warning regarding runtime
resume is gone.
So only the ordering issue needs to be addressed.
Best regards,
Alexander
--
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
http://www.tq-group.com/
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-05-15 9:11 ` Alexander Stein
@ 2023-05-15 12:04 ` Sverdlin, Alexander
2023-05-15 12:32 ` Alexander Stein
0 siblings, 1 reply; 14+ messages in thread
From: Sverdlin, Alexander @ 2023-05-15 12:04 UTC (permalink / raw)
To: alexander.stein
Cc: linux-imx, kernel, s.hauer, festevam, shawnguo, linux-kernel,
linux-arm-kernel, linux-i2c, aisheng.dong
Hello Alexander!
On Mon, 2023-05-15 at 11:11 +0200, Alexander Stein wrote:
> > [ 22.503179] other info that might help us debug this:
> > [ 22.503179]
> > [ 22.503183] Chain exists of:
> > [ 22.503183] prepare_lock --> rtc_pcf85063:594:(&config-
> > >regmap)->lock
> > --> i2c_register_adapter
> > [ 22.503183]
> > [ 22.503207] Possible unsafe locking scenario:
> > [ 22.503207]
> > [ 22.503210] CPU0 CPU1
> > [ 22.503213] ---- ----
> > [ 22.503216] lock(i2c_register_adapter);
> > [ 22.503225]
> > lock(rtc_pcf85063:594:(&config-
> > > regmap)->lock);
> >
> > [ 22.503235]
> > lock(i2c_register_adapter);
> > [ 22.503244] lock(prepare_lock);
> > [ 22.503253]
> > [ 22.503253] *** DEADLOCK ***
> >
> > Now lpi2c_runtime_resume will call into clk_prepare() which also
> > calls
> > clk_prepare_lock() (identical to clk_get_rate).
> >
> > Best regards,
> > Alexader
> >
> > > pm_runtime_set_autosuspend_delay(&pdev->dev,
> > > I2C_PM_TIMEOUT);
> > > pm_runtime_use_autosuspend(&pdev->dev);
> > > pm_runtime_get_noresume(&pdev->dev);
>
> With commit fa39065833db ("i2c: imx-lpi2c: avoid taking clk_prepare
> mutex in
> PM callbacks") in place, the additional deadlock warning regarding
> runtime
> resume is gone.
> So only the ordering issue needs to be addressed.
Unfortunately with both your (backported) and my patches applied I've
got a 3rd warning:
======================================================
WARNING: possible circular locking dependency detected
5.15.71+git8e43aee #1 Tainted: G O
------------------------------------------------------
xxxxxxx/2238 is trying to acquire lock:
ffff0000040bda40 (&desc->request_mutex){+.+.}-{3:3}, at:
__setup_irq+0xbc/0x8bc
but task is already holding lock:
ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
i2c_adapter_lock_bus+0x2c/0x3c
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (i2c_register_adapter){+.+.}-{3:3}:
lock_acquire+0x68/0x84
rt_mutex_lock_nested+0x88/0xe0
i2c_adapter_lock_bus+0x2c/0x3c
i2c_transfer+0x58/0x130
regmap_i2c_read+0x64/0xb0
_regmap_raw_read+0x114/0x440
_regmap_bus_read+0x4c/0x84
_regmap_read+0x6c/0x270
regmap_read+0x54/0x80
pcf85063_probe+0xec/0x4cc
i2c_device_probe+0x10c/0x350
really_probe+0xc4/0x470
__driver_probe_device+0x11c/0x190
driver_probe_device+0x48/0x110
__device_attach_driver+0xc4/0x160
bus_for_each_drv+0x80/0xe0
__device_attach+0xb0/0x1f0
device_initial_probe+0x1c/0x2c
bus_probe_device+0xa4/0xb0
device_add+0x398/0x8ac
device_register+0x28/0x40
i2c_new_client_device+0x144/0x290
of_i2c_register_devices+0x18c/0x230
i2c_register_adapter+0x1dc/0x6b0
__i2c_add_numbered_adapter+0x68/0xbc
i2c_add_adapter+0xb0/0xe0
lpi2c_imx_probe+0x3a4/0x670
platform_probe+0x70/0xec
really_probe+0xc4/0x470
__driver_probe_device+0x11c/0x190
driver_probe_device+0x48/0x110
__device_attach_driver+0xc4/0x160
bus_for_each_drv+0x80/0xe0
__device_attach+0xb0/0x1f0
device_initial_probe+0x1c/0x2c
bus_probe_device+0xa4/0xb0
deferred_probe_work_func+0xb8/0x110
process_one_work+0x27c/0x6c4
worker_thread+0x7c/0x450
kthread+0x168/0x17c
ret_from_fork+0x10/0x20
-> #4 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
lock_acquire+0x68/0x84
__mutex_lock+0xa8/0x4d0
mutex_lock_nested+0x48/0x54
regmap_lock_mutex+0x1c/0x30
regmap_read+0x44/0x80
pcf85063_clkout_recalc_rate+0x34/0x80
__clk_register+0x520/0x880
devm_clk_register+0x64/0xc4
pcf85063_probe+0x24c/0x4cc
i2c_device_probe+0x10c/0x350
really_probe+0xc4/0x470
__driver_probe_device+0x11c/0x190
driver_probe_device+0x48/0x110
__device_attach_driver+0xc4/0x160
bus_for_each_drv+0x80/0xe0
__device_attach+0xb0/0x1f0
device_initial_probe+0x1c/0x2c
bus_probe_device+0xa4/0xb0
device_add+0x398/0x8ac
device_register+0x28/0x40
i2c_new_client_device+0x144/0x290
of_i2c_register_devices+0x18c/0x230
i2c_register_adapter+0x1dc/0x6b0
__i2c_add_numbered_adapter+0x68/0xbc
i2c_add_adapter+0xb0/0xe0
lpi2c_imx_probe+0x3a4/0x670
platform_probe+0x70/0xec
really_probe+0xc4/0x470
__driver_probe_device+0x11c/0x190
driver_probe_device+0x48/0x110
__device_attach_driver+0xc4/0x160
bus_for_each_drv+0x80/0xe0
__device_attach+0xb0/0x1f0
device_initial_probe+0x1c/0x2c
bus_probe_device+0xa4/0xb0
deferred_probe_work_func+0xb8/0x110
process_one_work+0x27c/0x6c4
worker_thread+0x7c/0x450
kthread+0x168/0x17c
ret_from_fork+0x10/0x20
-> #3 (prepare_lock){+.+.}-{3:3}:
lock_acquire+0x68/0x84
__mutex_lock+0xa8/0x4d0
mutex_lock_nested+0x48/0x54
clk_prepare_lock+0x50/0xb0
clk_prepare+0x28/0x50
fec_runtime_resume+0x3c/0xe0
pm_generic_runtime_resume+0x34/0x50
__genpd_runtime_resume+0x38/0x90
genpd_runtime_resume+0xa0/0x304
__rpm_callback+0x50/0x1b0
rpm_callback+0x40/0x80
rpm_resume+0x448/0x6e0
__pm_runtime_resume+0x50/0xc0
fec_enet_mdio_read+0x48/0x190
__mdiobus_read+0x48/0xb0
mdiobus_read_nested+0x48/0x70
mv88e6xxx_smi_dual_direct_read+0x2c/0x50
mv88e6xxx_read+0x64/0xf0
mv88e6xxx_g1_read+0x28/0x34
mv88e6xxx_g1_irq_thread_work+0x50/0x17c
mv88e6xxx_irq_poll+0x28/0x50
kthread_worker_fn+0x100/0x480
kthread+0x168/0x17c
ret_from_fork+0x10/0x20
-> #2 (&bus->mdio_lock/2){+.+.}-{3:3}:
lock_acquire+0x68/0x84
__mutex_lock+0xa8/0x4d0
mutex_lock_nested+0x48/0x54
mdiobus_read_nested+0x38/0x70
mv88e6xxx_smi_dual_direct_read+0x2c/0x50
mv88e6xxx_read+0x64/0xf0
mv88e6xxx_port_read+0x24/0x30
mv88e6xxx_probe+0x250/0x7f0
mdio_probe+0x3c/0x80
really_probe+0xc4/0x470
__driver_probe_device+0x11c/0x190
driver_probe_device+0x48/0x110
__device_attach_driver+0xc4/0x160
bus_for_each_drv+0x80/0xe0
__device_attach+0xb0/0x1f0
device_initial_probe+0x1c/0x2c
bus_probe_device+0xa4/0xb0
deferred_probe_work_func+0xb8/0x110
process_one_work+0x27c/0x6c4
worker_thread+0x7c/0x450
kthread+0x168/0x17c
ret_from_fork+0x10/0x20
-> #1 (&chip->reg_lock){+.+.}-{3:3}:
lock_acquire+0x68/0x84
__mutex_lock+0xa8/0x4d0
mutex_lock_nested+0x48/0x54
mv88e6xxx_g1_irq_bus_lock+0x24/0x30
__setup_irq+0x6e0/0x8bc
request_threaded_irq+0xf4/0x1b4
mv88e6xxx_g2_irq_setup+0x1f0/0x2b4
mv88e6xxx_probe+0x480/0x7f0
mdio_probe+0x3c/0x80
really_probe+0xc4/0x470
__driver_probe_device+0x11c/0x190
driver_probe_device+0x48/0x110
__device_attach_driver+0xc4/0x160
bus_for_each_drv+0x80/0xe0
__device_attach+0xb0/0x1f0
device_initial_probe+0x1c/0x2c
bus_probe_device+0xa4/0xb0
deferred_probe_work_func+0xb8/0x110
process_one_work+0x27c/0x6c4
worker_thread+0x7c/0x450
kthread+0x168/0x17c
ret_from_fork+0x10/0x20
-> #0 (&desc->request_mutex){+.+.}-{3:3}:
__lock_acquire+0x12a4/0x20a0
lock_acquire.part.0+0xe0/0x230
lock_acquire+0x68/0x84
__mutex_lock+0xa8/0x4d0
mutex_lock_nested+0x48/0x54
__setup_irq+0xbc/0x8bc
request_threaded_irq+0xf4/0x1b4
devm_request_threaded_irq+0x88/0x104
lpi2c_runtime_resume+0x70/0xe4
pm_generic_runtime_resume+0x34/0x50
__genpd_runtime_resume+0x38/0x90
genpd_runtime_resume+0xa0/0x304
__rpm_callback+0x50/0x1b0
rpm_callback+0x74/0x80
rpm_resume+0x448/0x6e0
__pm_runtime_resume+0x50/0xc0
lpi2c_imx_xfer+0x60/0xa5c
__i2c_transfer+0x174/0xa80
i2c_transfer+0x68/0x130
regmap_i2c_read+0x64/0xb0
_regmap_raw_read+0x114/0x440
regmap_raw_read+0x19c/0x28c
regmap_bulk_read+0x1b8/0x244
at24_read+0x14c/0x2c4
nvmem_reg_read+0x2c/0x54
bin_attr_nvmem_read+0x8c/0xbc
sysfs_kf_bin_read+0x74/0x94
kernfs_fop_read_iter+0xb0/0x1d0
new_sync_read+0xf0/0x184
vfs_read+0x154/0x1f0
ksys_read+0x70/0x100
__arm64_sys_read+0x24/0x30
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0x68/0x124
do_el0_svc+0x30/0x9c
el0_svc+0x54/0x110
el0t_64_sync_handler+0xa4/0x130
el0t_64_sync+0x1a0/0x1a4
other info that might help us debug this:
Chain exists of:
&desc->request_mutex --> rtc_pcf85063:560:(&config->regmap)->lock -->
i2c_register_adapter
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(i2c_register_adapter);
lock(rtc_pcf85063:560:(&config->regmap)-
>lock);
lock(i2c_register_adapter);
lock(&desc->request_mutex);
*** DEADLOCK ***
4 locks held by xxxxxxx/2238:
#0: ffff000015a64488 (&of->mutex){+.+.}-{3:3}, at:
kernfs_fop_read_iter+0x74/0x1d0
#1: ffff0000119e2400 (kn->active#58){.+.+}-{0:0}, at:
kernfs_fop_read_iter+0x7c/0x1d0
#2: ffff0000119a26e8 (&at24->lock){+.+.}-{3:3}, at:
at24_read+0x8c/0x2c4
#3: ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
i2c_adapter_lock_bus+0x2c/0x3c
stack backtrace:
CPU: 1 PID: 2238 Comm: xxxxxxx Tainted: G O
5.15.71+git8e43aee #1
Hardware name: Siemens PXC5.E24 (DT)
Call trace:
dump_backtrace+0x0/0x1d4
show_stack+0x20/0x2c
dump_stack_lvl+0x8c/0xb8
dump_stack+0x18/0x34
print_circular_bug+0x1f8/0x200
check_noncircular+0x130/0x144
__lock_acquire+0x12a4/0x20a0
lock_acquire.part.0+0xe0/0x230
lock_acquire+0x68/0x84
__mutex_lock+0xa8/0x4d0
mutex_lock_nested+0x48/0x54
__setup_irq+0xbc/0x8bc
request_threaded_irq+0xf4/0x1b4
devm_request_threaded_irq+0x88/0x104
lpi2c_runtime_resume+0x70/0xe4
pm_generic_runtime_resume+0x34/0x50
__genpd_runtime_resume+0x38/0x90
genpd_runtime_resume+0xa0/0x304
__rpm_callback+0x50/0x1b0
rpm_callback+0x74/0x80
rpm_resume+0x448/0x6e0
__pm_runtime_resume+0x50/0xc0
lpi2c_imx_xfer+0x60/0xa5c
__i2c_transfer+0x174/0xa80
i2c_transfer+0x68/0x130
regmap_i2c_read+0x64/0xb0
_regmap_raw_read+0x114/0x440
regmap_raw_read+0x19c/0x28c
regmap_bulk_read+0x1b8/0x244
at24_read+0x14c/0x2c4
nvmem_reg_read+0x2c/0x54
bin_attr_nvmem_read+0x8c/0xbc
sysfs_kf_bin_read+0x74/0x94
kernfs_fop_read_iter+0xb0/0x1d0
new_sync_read+0xf0/0x184
vfs_read+0x154/0x1f0
ksys_read+0x70/0x100
__arm64_sys_read+0x24/0x30
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0x68/0x124
do_el0_svc+0x30/0x9c
el0_svc+0x54/0x110
el0t_64_sync_handler+0xa4/0x130
el0t_64_sync+0x1a0/0x1a4
So this doesn't look like an end of the story yet, unfortunately.
--
Alexander Sverdlin
Siemens AG
www.siemens.com
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-05-15 12:04 ` Sverdlin, Alexander
@ 2023-05-15 12:32 ` Alexander Stein
2023-05-15 12:37 ` Sverdlin, Alexander
0 siblings, 1 reply; 14+ messages in thread
From: Alexander Stein @ 2023-05-15 12:32 UTC (permalink / raw)
To: Sverdlin, Alexander
Cc: linux-imx, kernel, s.hauer, festevam, shawnguo, linux-kernel,
linux-arm-kernel, linux-i2c, aisheng.dong
Hi Alexander,
Am Montag, 15. Mai 2023, 14:04:10 CEST schrieb Sverdlin, Alexander:
> Hello Alexander!
>
> On Mon, 2023-05-15 at 11:11 +0200, Alexander Stein wrote:
>
> > > [ 22.503179] other info that might help us debug this:
> > > [ 22.503179]
> > > [ 22.503183] Chain exists of:
> > > [ 22.503183] prepare_lock --> rtc_pcf85063:594:(&config-
> > >
> > > >regmap)->lock
> > >
> > > --> i2c_register_adapter
> > > [ 22.503183]
> > > [ 22.503207] Possible unsafe locking scenario:
> > > [ 22.503207]
> > > [ 22.503210] CPU0 CPU1
> > > [ 22.503213] ---- ----
> > > [ 22.503216] lock(i2c_register_adapter);
> > > [ 22.503225]
> > > lock(rtc_pcf85063:594:(&config-
> > >
> > > > regmap)->lock);
> > >
> > >
> > > [ 22.503235]
> > > lock(i2c_register_adapter);
> > > [ 22.503244] lock(prepare_lock);
> > > [ 22.503253]
> > > [ 22.503253] *** DEADLOCK ***
> > >
> > > Now lpi2c_runtime_resume will call into clk_prepare() which also
> > > calls
> > > clk_prepare_lock() (identical to clk_get_rate).
> > >
> > > Best regards,
> > > Alexader
> > >
> > >
> > > > pm_runtime_set_autosuspend_delay(&pdev->dev,
> > > > I2C_PM_TIMEOUT);
> > > > pm_runtime_use_autosuspend(&pdev->dev);
> > > > pm_runtime_get_noresume(&pdev->dev);
> >
> >
> > With commit fa39065833db ("i2c: imx-lpi2c: avoid taking clk_prepare
> > mutex in
> > PM callbacks") in place, the additional deadlock warning regarding
> > runtime
> > resume is gone.
> > So only the ordering issue needs to be addressed.
>
>
> Unfortunately with both your (backported) and my patches applied I've
> got a 3rd warning:
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.15.71+git8e43aee #1 Tainted: G O
> ------------------------------------------------------
> xxxxxxx/2238 is trying to acquire lock:
> ffff0000040bda40 (&desc->request_mutex){+.+.}-{3:3}, at:
> __setup_irq+0xbc/0x8bc
>
> but task is already holding lock:
> ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus+0x2c/0x3c
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #5 (i2c_register_adapter){+.+.}-{3:3}:
> lock_acquire+0x68/0x84
> rt_mutex_lock_nested+0x88/0xe0
> i2c_adapter_lock_bus+0x2c/0x3c
> i2c_transfer+0x58/0x130
> regmap_i2c_read+0x64/0xb0
> _regmap_raw_read+0x114/0x440
> _regmap_bus_read+0x4c/0x84
> _regmap_read+0x6c/0x270
> regmap_read+0x54/0x80
> pcf85063_probe+0xec/0x4cc
> i2c_device_probe+0x10c/0x350
> really_probe+0xc4/0x470
> __driver_probe_device+0x11c/0x190
> driver_probe_device+0x48/0x110
> __device_attach_driver+0xc4/0x160
> bus_for_each_drv+0x80/0xe0
> __device_attach+0xb0/0x1f0
> device_initial_probe+0x1c/0x2c
> bus_probe_device+0xa4/0xb0
> device_add+0x398/0x8ac
> device_register+0x28/0x40
> i2c_new_client_device+0x144/0x290
> of_i2c_register_devices+0x18c/0x230
> i2c_register_adapter+0x1dc/0x6b0
> __i2c_add_numbered_adapter+0x68/0xbc
> i2c_add_adapter+0xb0/0xe0
> lpi2c_imx_probe+0x3a4/0x670
> platform_probe+0x70/0xec
> really_probe+0xc4/0x470
> __driver_probe_device+0x11c/0x190
> driver_probe_device+0x48/0x110
> __device_attach_driver+0xc4/0x160
> bus_for_each_drv+0x80/0xe0
> __device_attach+0xb0/0x1f0
> device_initial_probe+0x1c/0x2c
> bus_probe_device+0xa4/0xb0
> deferred_probe_work_func+0xb8/0x110
> process_one_work+0x27c/0x6c4
> worker_thread+0x7c/0x450
> kthread+0x168/0x17c
> ret_from_fork+0x10/0x20
>
> -> #4 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
> lock_acquire+0x68/0x84
> __mutex_lock+0xa8/0x4d0
> mutex_lock_nested+0x48/0x54
> regmap_lock_mutex+0x1c/0x30
> regmap_read+0x44/0x80
> pcf85063_clkout_recalc_rate+0x34/0x80
> __clk_register+0x520/0x880
> devm_clk_register+0x64/0xc4
> pcf85063_probe+0x24c/0x4cc
> i2c_device_probe+0x10c/0x350
> really_probe+0xc4/0x470
> __driver_probe_device+0x11c/0x190
> driver_probe_device+0x48/0x110
> __device_attach_driver+0xc4/0x160
> bus_for_each_drv+0x80/0xe0
> __device_attach+0xb0/0x1f0
> device_initial_probe+0x1c/0x2c
> bus_probe_device+0xa4/0xb0
> device_add+0x398/0x8ac
> device_register+0x28/0x40
> i2c_new_client_device+0x144/0x290
> of_i2c_register_devices+0x18c/0x230
> i2c_register_adapter+0x1dc/0x6b0
> __i2c_add_numbered_adapter+0x68/0xbc
> i2c_add_adapter+0xb0/0xe0
> lpi2c_imx_probe+0x3a4/0x670
> platform_probe+0x70/0xec
> really_probe+0xc4/0x470
> __driver_probe_device+0x11c/0x190
> driver_probe_device+0x48/0x110
> __device_attach_driver+0xc4/0x160
> bus_for_each_drv+0x80/0xe0
> __device_attach+0xb0/0x1f0
> device_initial_probe+0x1c/0x2c
> bus_probe_device+0xa4/0xb0
> deferred_probe_work_func+0xb8/0x110
> process_one_work+0x27c/0x6c4
> worker_thread+0x7c/0x450
> kthread+0x168/0x17c
> ret_from_fork+0x10/0x20
>
> -> #3 (prepare_lock){+.+.}-{3:3}:
> lock_acquire+0x68/0x84
> __mutex_lock+0xa8/0x4d0
> mutex_lock_nested+0x48/0x54
> clk_prepare_lock+0x50/0xb0
> clk_prepare+0x28/0x50
> fec_runtime_resume+0x3c/0xe0
> pm_generic_runtime_resume+0x34/0x50
> __genpd_runtime_resume+0x38/0x90
> genpd_runtime_resume+0xa0/0x304
> __rpm_callback+0x50/0x1b0
> rpm_callback+0x40/0x80
> rpm_resume+0x448/0x6e0
> __pm_runtime_resume+0x50/0xc0
> fec_enet_mdio_read+0x48/0x190
> __mdiobus_read+0x48/0xb0
> mdiobus_read_nested+0x48/0x70
> mv88e6xxx_smi_dual_direct_read+0x2c/0x50
> mv88e6xxx_read+0x64/0xf0
> mv88e6xxx_g1_read+0x28/0x34
> mv88e6xxx_g1_irq_thread_work+0x50/0x17c
> mv88e6xxx_irq_poll+0x28/0x50
> kthread_worker_fn+0x100/0x480
> kthread+0x168/0x17c
> ret_from_fork+0x10/0x20
>
> -> #2 (&bus->mdio_lock/2){+.+.}-{3:3}:
> lock_acquire+0x68/0x84
> __mutex_lock+0xa8/0x4d0
> mutex_lock_nested+0x48/0x54
> mdiobus_read_nested+0x38/0x70
> mv88e6xxx_smi_dual_direct_read+0x2c/0x50
> mv88e6xxx_read+0x64/0xf0
> mv88e6xxx_port_read+0x24/0x30
> mv88e6xxx_probe+0x250/0x7f0
> mdio_probe+0x3c/0x80
> really_probe+0xc4/0x470
> __driver_probe_device+0x11c/0x190
> driver_probe_device+0x48/0x110
> __device_attach_driver+0xc4/0x160
> bus_for_each_drv+0x80/0xe0
> __device_attach+0xb0/0x1f0
> device_initial_probe+0x1c/0x2c
> bus_probe_device+0xa4/0xb0
> deferred_probe_work_func+0xb8/0x110
> process_one_work+0x27c/0x6c4
> worker_thread+0x7c/0x450
> kthread+0x168/0x17c
> ret_from_fork+0x10/0x20
>
> -> #1 (&chip->reg_lock){+.+.}-{3:3}:
> lock_acquire+0x68/0x84
> __mutex_lock+0xa8/0x4d0
> mutex_lock_nested+0x48/0x54
> mv88e6xxx_g1_irq_bus_lock+0x24/0x30
> __setup_irq+0x6e0/0x8bc
> request_threaded_irq+0xf4/0x1b4
> mv88e6xxx_g2_irq_setup+0x1f0/0x2b4
> mv88e6xxx_probe+0x480/0x7f0
> mdio_probe+0x3c/0x80
> really_probe+0xc4/0x470
> __driver_probe_device+0x11c/0x190
> driver_probe_device+0x48/0x110
> __device_attach_driver+0xc4/0x160
> bus_for_each_drv+0x80/0xe0
> __device_attach+0xb0/0x1f0
> device_initial_probe+0x1c/0x2c
> bus_probe_device+0xa4/0xb0
> deferred_probe_work_func+0xb8/0x110
> process_one_work+0x27c/0x6c4
> worker_thread+0x7c/0x450
> kthread+0x168/0x17c
> ret_from_fork+0x10/0x20
>
> -> #0 (&desc->request_mutex){+.+.}-{3:3}:
> __lock_acquire+0x12a4/0x20a0
> lock_acquire.part.0+0xe0/0x230
> lock_acquire+0x68/0x84
> __mutex_lock+0xa8/0x4d0
> mutex_lock_nested+0x48/0x54
> __setup_irq+0xbc/0x8bc
> request_threaded_irq+0xf4/0x1b4
> devm_request_threaded_irq+0x88/0x104
> lpi2c_runtime_resume+0x70/0xe4
This looks like the NXP downstream kernel, requesting the IRQ from within
runtime resume.
> pm_generic_runtime_resume+0x34/0x50
> __genpd_runtime_resume+0x38/0x90
> genpd_runtime_resume+0xa0/0x304
> __rpm_callback+0x50/0x1b0
> rpm_callback+0x74/0x80
> rpm_resume+0x448/0x6e0
> __pm_runtime_resume+0x50/0xc0
> lpi2c_imx_xfer+0x60/0xa5c
> __i2c_transfer+0x174/0xa80
> i2c_transfer+0x68/0x130
> regmap_i2c_read+0x64/0xb0
> _regmap_raw_read+0x114/0x440
> regmap_raw_read+0x19c/0x28c
> regmap_bulk_read+0x1b8/0x244
> at24_read+0x14c/0x2c4
> nvmem_reg_read+0x2c/0x54
> bin_attr_nvmem_read+0x8c/0xbc
> sysfs_kf_bin_read+0x74/0x94
> kernfs_fop_read_iter+0xb0/0x1d0
> new_sync_read+0xf0/0x184
> vfs_read+0x154/0x1f0
> ksys_read+0x70/0x100
> __arm64_sys_read+0x24/0x30
> invoke_syscall+0x50/0x120
> el0_svc_common.constprop.0+0x68/0x124
> do_el0_svc+0x30/0x9c
> el0_svc+0x54/0x110
> el0t_64_sync_handler+0xa4/0x130
> el0t_64_sync+0x1a0/0x1a4
>
> other info that might help us debug this:
>
> Chain exists of:
> &desc->request_mutex --> rtc_pcf85063:560:(&config->regmap)->lock -->
> i2c_register_adapter
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(i2c_register_adapter);
> lock(rtc_pcf85063:560:(&config->regmap)-
>
> >lock);
>
> lock(i2c_register_adapter);
> lock(&desc->request_mutex);
>
> *** DEADLOCK ***
>
> 4 locks held by xxxxxxx/2238:
> #0: ffff000015a64488 (&of->mutex){+.+.}-{3:3}, at:
> kernfs_fop_read_iter+0x74/0x1d0
> #1: ffff0000119e2400 (kn->active#58){.+.+}-{0:0}, at:
> kernfs_fop_read_iter+0x7c/0x1d0
> #2: ffff0000119a26e8 (&at24->lock){+.+.}-{3:3}, at:
> at24_read+0x8c/0x2c4
> #3: ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
> i2c_adapter_lock_bus+0x2c/0x3c
>
> stack backtrace:
> CPU: 1 PID: 2238 Comm: xxxxxxx Tainted: G O
> 5.15.71+git8e43aee #1
> Hardware name: Siemens PXC5.E24 (DT)
> Call trace:
> dump_backtrace+0x0/0x1d4
> show_stack+0x20/0x2c
> dump_stack_lvl+0x8c/0xb8
> dump_stack+0x18/0x34
> print_circular_bug+0x1f8/0x200
> check_noncircular+0x130/0x144
> __lock_acquire+0x12a4/0x20a0
> lock_acquire.part.0+0xe0/0x230
> lock_acquire+0x68/0x84
> __mutex_lock+0xa8/0x4d0
> mutex_lock_nested+0x48/0x54
> __setup_irq+0xbc/0x8bc
> request_threaded_irq+0xf4/0x1b4
> devm_request_threaded_irq+0x88/0x104
> lpi2c_runtime_resume+0x70/0xe4
It seems your (possible) deadlock is triggered along devm_request_irq() during
resume.
As mainline just enables the clocks, there is nothing we can do here. Your
patch still is sensible, can you send a new version with the review addressed?
Thanks.
Best regards,
Alexander
> pm_generic_runtime_resume+0x34/0x50
> __genpd_runtime_resume+0x38/0x90
> genpd_runtime_resume+0xa0/0x304
> __rpm_callback+0x50/0x1b0
> rpm_callback+0x74/0x80
> rpm_resume+0x448/0x6e0
> __pm_runtime_resume+0x50/0xc0
> lpi2c_imx_xfer+0x60/0xa5c
> __i2c_transfer+0x174/0xa80
> i2c_transfer+0x68/0x130
> regmap_i2c_read+0x64/0xb0
> _regmap_raw_read+0x114/0x440
> regmap_raw_read+0x19c/0x28c
> regmap_bulk_read+0x1b8/0x244
> at24_read+0x14c/0x2c4
> nvmem_reg_read+0x2c/0x54
> bin_attr_nvmem_read+0x8c/0xbc
> sysfs_kf_bin_read+0x74/0x94
> kernfs_fop_read_iter+0xb0/0x1d0
> new_sync_read+0xf0/0x184
> vfs_read+0x154/0x1f0
> ksys_read+0x70/0x100
> __arm64_sys_read+0x24/0x30
> invoke_syscall+0x50/0x120
> el0_svc_common.constprop.0+0x68/0x124
> do_el0_svc+0x30/0x9c
> el0_svc+0x54/0x110
> el0t_64_sync_handler+0xa4/0x130
> el0t_64_sync+0x1a0/0x1a4
>
> So this doesn't look like an end of the story yet, unfortunately.
>
> --
> Alexander Sverdlin
> Siemens AG
> www.siemens.com
--
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
http://www.tq-group.com/
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-05-15 12:32 ` Alexander Stein
@ 2023-05-15 12:37 ` Sverdlin, Alexander
0 siblings, 0 replies; 14+ messages in thread
From: Sverdlin, Alexander @ 2023-05-15 12:37 UTC (permalink / raw)
To: alexander.stein
Cc: linux-imx, kernel, s.hauer, festevam, linux-kernel, shawnguo,
linux-arm-kernel, linux-i2c, aisheng.dong
Hello Alexander!
On Mon, 2023-05-15 at 14:32 +0200, Alexander Stein wrote:
> > stack backtrace:
> > CPU: 1 PID: 2238 Comm: xxxxxxx Tainted: G O
> > 5.15.71+git8e43aee #1
> > Hardware name: Siemens PXC5.E24 (DT)
> > Call trace:
> > dump_backtrace+0x0/0x1d4
> > show_stack+0x20/0x2c
> > dump_stack_lvl+0x8c/0xb8
> > dump_stack+0x18/0x34
> > print_circular_bug+0x1f8/0x200
> > check_noncircular+0x130/0x144
> > __lock_acquire+0x12a4/0x20a0
> > lock_acquire.part.0+0xe0/0x230
> > lock_acquire+0x68/0x84
> > __mutex_lock+0xa8/0x4d0
> > mutex_lock_nested+0x48/0x54
> > __setup_irq+0xbc/0x8bc
> > request_threaded_irq+0xf4/0x1b4
> > devm_request_threaded_irq+0x88/0x104
> > lpi2c_runtime_resume+0x70/0xe4
>
> It seems your (possible) deadlock is triggered along
> devm_request_irq() during
> resume.
You are right! Thank you for looking into this!
> As mainline just enables the clocks, there is nothing we can do here.
> Your
> patch still is sensible, can you send a new version with the review
> addressed?
Sure, I'll do!
--
Alexander Sverdlin
Siemens AG
www.siemens.com
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate
2023-04-21 13:48 ` Alexander Stein
` (2 preceding siblings ...)
2023-05-15 9:11 ` Alexander Stein
@ 2023-05-15 13:11 ` Sverdlin, Alexander
3 siblings, 0 replies; 14+ messages in thread
From: Sverdlin, Alexander @ 2023-05-15 13:11 UTC (permalink / raw)
To: alexander.stein, linux-imx
Cc: kernel, s.hauer, festevam, shawnguo, linux-kernel,
linux-arm-kernel, linux-i2c, aisheng.dong
Hello Alexander,
On Fri, 2023-04-21 at 15:48 +0200, Alexander Stein wrote:
> > + lpi2c_imx->clk_change_nb.notifier_call =
> > lpi2c_imx_clk_change_cb;
> > + ret = devm_clk_notifier_register(&pdev->dev, lpi2c_imx-
> > >clks[0].clk,
> > + &lpi2c_imx-
> > >clk_change_nb);
> > + if (ret)
> > + return dev_err_probe(&pdev->dev, ret,
> > + "can't register peripheral
> > clock
> notifier\n");
> > + lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk);
> > + if (!lpi2c_imx->rate_per) {
> > + dev_err(&pdev->dev, "can't get I2C peripheral clock
> rate\n");
> > + return -EINVAL;
> > + }
> > +
>
> I would switch the order of the calls to devm_clk_notifier_register()
> and
> clk_get_rate(). AFAICS this looks like a possible lost update. The
> notifier
> might change rate_per before the (old) value from clk_get_rate is
> actually
> assigned.
just swapping would not be enough I believe, in the case update event
happens between clk_get_rate() and devm_clk_notifier_register(). I'll
think about it...
--
Alexander Sverdlin
Siemens AG
www.siemens.com
^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2023-05-15 13:13 UTC | newest]
Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-03-10 13:08 [PATCH v3] i2c: lpi2c: cache peripheral clock rate A. Sverdlin
2023-04-21 13:48 ` Alexander Stein
2023-04-21 13:59 ` Marc Kleine-Budde
2023-04-24 7:03 ` Alexander Stein
2023-04-30 7:05 ` Wolfram Sang
2023-05-02 6:50 ` Alexander Stein
2023-05-02 7:03 ` Marc Kleine-Budde
2023-04-21 14:10 ` Sverdlin, Alexander
2023-05-15 9:11 ` Alexander Stein
2023-05-15 12:04 ` Sverdlin, Alexander
2023-05-15 12:32 ` Alexander Stein
2023-05-15 12:37 ` Sverdlin, Alexander
2023-05-15 13:11 ` Sverdlin, Alexander
2023-04-24 8:08 ` Alexander Stein
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