backlight: pwm_bl: Use gpiod_get_value_cansleep() to get initial state
diff mbox series

Message ID 20190127145054.3770-1-wens@csie.org
State New
Headers show
Series
  • backlight: pwm_bl: Use gpiod_get_value_cansleep() to get initial state
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Commit Message

Chen-Yu Tsai Jan. 27, 2019, 2:50 p.m. UTC
gpiod_get_value() gives out a warning if access to the underlying gpiochip
requires sleeping, which is common for I2C based chips:

    WARNING: CPU: 0 PID: 77 at drivers/gpio/gpiolib.c:2500 gpiod_get_value+0xd0/0x100
    Modules linked in:
    CPU: 0 PID: 77 Comm: kworker/0:2 Not tainted 4.14.0-rc3-00589-gf32897915d48-dirty #90
    Hardware name: Allwinner sun4i/sun5i Families
    Workqueue: events deferred_probe_work_func
    [<c010ec50>] (unwind_backtrace) from [<c010b784>] (show_stack+0x10/0x14)
    [<c010b784>] (show_stack) from [<c0797224>] (dump_stack+0x88/0x9c)
    [<c0797224>] (dump_stack) from [<c0125b08>] (__warn+0xe8/0x100)
    [<c0125b08>] (__warn) from [<c0125bd0>] (warn_slowpath_null+0x20/0x28)
    [<c0125bd0>] (warn_slowpath_null) from [<c037069c>] (gpiod_get_value+0xd0/0x100)
    [<c037069c>] (gpiod_get_value) from [<c03778d0>] (pwm_backlight_probe+0x238/0x508)
    [<c03778d0>] (pwm_backlight_probe) from [<c0411a2c>] (platform_drv_probe+0x50/0xac)
    [<c0411a2c>] (platform_drv_probe) from [<c0410224>] (driver_probe_device+0x238/0x2e8)
    [<c0410224>] (driver_probe_device) from [<c040e820>] (bus_for_each_drv+0x44/0x94)
    [<c040e820>] (bus_for_each_drv) from [<c040ff0c>] (__device_attach+0xb0/0x114)
    [<c040ff0c>] (__device_attach) from [<c040f4f8>] (bus_probe_device+0x84/0x8c)
    [<c040f4f8>] (bus_probe_device) from [<c040f944>] (deferred_probe_work_func+0x50/0x14c)
    [<c040f944>] (deferred_probe_work_func) from [<c013be84>] (process_one_work+0x1ec/0x414)
    [<c013be84>] (process_one_work) from [<c013ce5c>] (worker_thread+0x2b0/0x5a0)
    [<c013ce5c>] (worker_thread) from [<c0141908>] (kthread+0x14c/0x154)
    [<c0141908>] (kthread) from [<c0107ab0>] (ret_from_fork+0x14/0x24)

This was missed in commit 0c9501f823a4 ("backlight: pwm_bl: Handle gpio
that can sleep"). The code was then moved to a separate function in
commit 7613c922315e ("backlight: pwm_bl: Move the checks for initial power
state to a separate function").

The only usage of gpiod_get_value() is during the probe stage, which is
safe to sleep in. Switch to gpiod_get_value_cansleep().

Fixes: 0c9501f823a4 ("backlight: pwm_bl: Handle gpio that can sleep")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
 drivers/video/backlight/pwm_bl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Maxime Ripard Jan. 28, 2019, 10:38 a.m. UTC | #1
On Sun, Jan 27, 2019 at 10:50:54PM +0800, Chen-Yu Tsai wrote:
> gpiod_get_value() gives out a warning if access to the underlying gpiochip
> requires sleeping, which is common for I2C based chips:
> 
>     WARNING: CPU: 0 PID: 77 at drivers/gpio/gpiolib.c:2500 gpiod_get_value+0xd0/0x100
>     Modules linked in:
>     CPU: 0 PID: 77 Comm: kworker/0:2 Not tainted 4.14.0-rc3-00589-gf32897915d48-dirty #90
>     Hardware name: Allwinner sun4i/sun5i Families
>     Workqueue: events deferred_probe_work_func
>     [<c010ec50>] (unwind_backtrace) from [<c010b784>] (show_stack+0x10/0x14)
>     [<c010b784>] (show_stack) from [<c0797224>] (dump_stack+0x88/0x9c)
>     [<c0797224>] (dump_stack) from [<c0125b08>] (__warn+0xe8/0x100)
>     [<c0125b08>] (__warn) from [<c0125bd0>] (warn_slowpath_null+0x20/0x28)
>     [<c0125bd0>] (warn_slowpath_null) from [<c037069c>] (gpiod_get_value+0xd0/0x100)
>     [<c037069c>] (gpiod_get_value) from [<c03778d0>] (pwm_backlight_probe+0x238/0x508)
>     [<c03778d0>] (pwm_backlight_probe) from [<c0411a2c>] (platform_drv_probe+0x50/0xac)
>     [<c0411a2c>] (platform_drv_probe) from [<c0410224>] (driver_probe_device+0x238/0x2e8)
>     [<c0410224>] (driver_probe_device) from [<c040e820>] (bus_for_each_drv+0x44/0x94)
>     [<c040e820>] (bus_for_each_drv) from [<c040ff0c>] (__device_attach+0xb0/0x114)
>     [<c040ff0c>] (__device_attach) from [<c040f4f8>] (bus_probe_device+0x84/0x8c)
>     [<c040f4f8>] (bus_probe_device) from [<c040f944>] (deferred_probe_work_func+0x50/0x14c)
>     [<c040f944>] (deferred_probe_work_func) from [<c013be84>] (process_one_work+0x1ec/0x414)
>     [<c013be84>] (process_one_work) from [<c013ce5c>] (worker_thread+0x2b0/0x5a0)
>     [<c013ce5c>] (worker_thread) from [<c0141908>] (kthread+0x14c/0x154)
>     [<c0141908>] (kthread) from [<c0107ab0>] (ret_from_fork+0x14/0x24)
> 
> This was missed in commit 0c9501f823a4 ("backlight: pwm_bl: Handle gpio
> that can sleep"). The code was then moved to a separate function in
> commit 7613c922315e ("backlight: pwm_bl: Move the checks for initial power
> state to a separate function").
> 
> The only usage of gpiod_get_value() is during the probe stage, which is
> safe to sleep in. Switch to gpiod_get_value_cansleep().
> 
> Fixes: 0c9501f823a4 ("backlight: pwm_bl: Handle gpio that can sleep")
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>

Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>

Maxime
Daniel Thompson Jan. 28, 2019, 11:05 a.m. UTC | #2
On Sun, Jan 27, 2019 at 10:50:54PM +0800, Chen-Yu Tsai wrote:
> gpiod_get_value() gives out a warning if access to the underlying gpiochip
> requires sleeping, which is common for I2C based chips:
> 
>     WARNING: CPU: 0 PID: 77 at drivers/gpio/gpiolib.c:2500 gpiod_get_value+0xd0/0x100
>     Modules linked in:
>     CPU: 0 PID: 77 Comm: kworker/0:2 Not tainted 4.14.0-rc3-00589-gf32897915d48-dirty #90
>     Hardware name: Allwinner sun4i/sun5i Families
>     Workqueue: events deferred_probe_work_func
>     [<c010ec50>] (unwind_backtrace) from [<c010b784>] (show_stack+0x10/0x14)
>     [<c010b784>] (show_stack) from [<c0797224>] (dump_stack+0x88/0x9c)
>     [<c0797224>] (dump_stack) from [<c0125b08>] (__warn+0xe8/0x100)
>     [<c0125b08>] (__warn) from [<c0125bd0>] (warn_slowpath_null+0x20/0x28)
>     [<c0125bd0>] (warn_slowpath_null) from [<c037069c>] (gpiod_get_value+0xd0/0x100)
>     [<c037069c>] (gpiod_get_value) from [<c03778d0>] (pwm_backlight_probe+0x238/0x508)
>     [<c03778d0>] (pwm_backlight_probe) from [<c0411a2c>] (platform_drv_probe+0x50/0xac)
>     [<c0411a2c>] (platform_drv_probe) from [<c0410224>] (driver_probe_device+0x238/0x2e8)
>     [<c0410224>] (driver_probe_device) from [<c040e820>] (bus_for_each_drv+0x44/0x94)
>     [<c040e820>] (bus_for_each_drv) from [<c040ff0c>] (__device_attach+0xb0/0x114)
>     [<c040ff0c>] (__device_attach) from [<c040f4f8>] (bus_probe_device+0x84/0x8c)
>     [<c040f4f8>] (bus_probe_device) from [<c040f944>] (deferred_probe_work_func+0x50/0x14c)
>     [<c040f944>] (deferred_probe_work_func) from [<c013be84>] (process_one_work+0x1ec/0x414)
>     [<c013be84>] (process_one_work) from [<c013ce5c>] (worker_thread+0x2b0/0x5a0)
>     [<c013ce5c>] (worker_thread) from [<c0141908>] (kthread+0x14c/0x154)
>     [<c0141908>] (kthread) from [<c0107ab0>] (ret_from_fork+0x14/0x24)
> 
> This was missed in commit 0c9501f823a4 ("backlight: pwm_bl: Handle gpio
> that can sleep"). The code was then moved to a separate function in
> commit 7613c922315e ("backlight: pwm_bl: Move the checks for initial power
> state to a separate function").
> 
> The only usage of gpiod_get_value() is during the probe stage, which is
> safe to sleep in. Switch to gpiod_get_value_cansleep().
> 
> Fixes: 0c9501f823a4 ("backlight: pwm_bl: Handle gpio that can sleep")
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>


Acked-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

> ---
>  drivers/video/backlight/pwm_bl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index feb90764a811..53b8ceea9bde 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -435,7 +435,7 @@ static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
>  	 */
>  
>  	/* if the enable GPIO is disabled, do not enable the backlight */
> -	if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
> +	if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
>  		return FB_BLANK_POWERDOWN;
>  
>  	/* The regulator is disabled, do not enable the backlight */
> -- 
> 2.20.1
>
Lee Jones Jan. 30, 2019, 1:36 p.m. UTC | #3
On Sun, 27 Jan 2019, Chen-Yu Tsai wrote:

> gpiod_get_value() gives out a warning if access to the underlying gpiochip
> requires sleeping, which is common for I2C based chips:
> 
>     WARNING: CPU: 0 PID: 77 at drivers/gpio/gpiolib.c:2500 gpiod_get_value+0xd0/0x100
>     Modules linked in:
>     CPU: 0 PID: 77 Comm: kworker/0:2 Not tainted 4.14.0-rc3-00589-gf32897915d48-dirty #90
>     Hardware name: Allwinner sun4i/sun5i Families
>     Workqueue: events deferred_probe_work_func
>     [<c010ec50>] (unwind_backtrace) from [<c010b784>] (show_stack+0x10/0x14)
>     [<c010b784>] (show_stack) from [<c0797224>] (dump_stack+0x88/0x9c)
>     [<c0797224>] (dump_stack) from [<c0125b08>] (__warn+0xe8/0x100)
>     [<c0125b08>] (__warn) from [<c0125bd0>] (warn_slowpath_null+0x20/0x28)
>     [<c0125bd0>] (warn_slowpath_null) from [<c037069c>] (gpiod_get_value+0xd0/0x100)
>     [<c037069c>] (gpiod_get_value) from [<c03778d0>] (pwm_backlight_probe+0x238/0x508)
>     [<c03778d0>] (pwm_backlight_probe) from [<c0411a2c>] (platform_drv_probe+0x50/0xac)
>     [<c0411a2c>] (platform_drv_probe) from [<c0410224>] (driver_probe_device+0x238/0x2e8)
>     [<c0410224>] (driver_probe_device) from [<c040e820>] (bus_for_each_drv+0x44/0x94)
>     [<c040e820>] (bus_for_each_drv) from [<c040ff0c>] (__device_attach+0xb0/0x114)
>     [<c040ff0c>] (__device_attach) from [<c040f4f8>] (bus_probe_device+0x84/0x8c)
>     [<c040f4f8>] (bus_probe_device) from [<c040f944>] (deferred_probe_work_func+0x50/0x14c)
>     [<c040f944>] (deferred_probe_work_func) from [<c013be84>] (process_one_work+0x1ec/0x414)
>     [<c013be84>] (process_one_work) from [<c013ce5c>] (worker_thread+0x2b0/0x5a0)
>     [<c013ce5c>] (worker_thread) from [<c0141908>] (kthread+0x14c/0x154)
>     [<c0141908>] (kthread) from [<c0107ab0>] (ret_from_fork+0x14/0x24)
> 
> This was missed in commit 0c9501f823a4 ("backlight: pwm_bl: Handle gpio
> that can sleep"). The code was then moved to a separate function in
> commit 7613c922315e ("backlight: pwm_bl: Move the checks for initial power
> state to a separate function").
> 
> The only usage of gpiod_get_value() is during the probe stage, which is
> safe to sleep in. Switch to gpiod_get_value_cansleep().
> 
> Fixes: 0c9501f823a4 ("backlight: pwm_bl: Handle gpio that can sleep")
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>
> ---
>  drivers/video/backlight/pwm_bl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks.

Patch
diff mbox series

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index feb90764a811..53b8ceea9bde 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -435,7 +435,7 @@  static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 	 */
 
 	/* if the enable GPIO is disabled, do not enable the backlight */
-	if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
+	if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
 		return FB_BLANK_POWERDOWN;
 
 	/* The regulator is disabled, do not enable the backlight */