[PATCH v4] backlight: pwm_bl: Disable PWM on shutdown, suspend and remove

[Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>]

Since commit 00e7e698bff1 ("backlight: pwm_bl: Configure pwm only once
per backlight toggle") calling pwm_backlight_power_off() doesn't disable
the PWM any more. However this is necessary to suspend because PWM
drivers usually refuse to suspend if they are still enabled.

Also adapt shutdown and remove callbacks to disable the PWM for similar
reasons.

Fixes: 00e7e698bff1 ("backlight: pwm_bl: Configure pwm only once per backlight toggle")
Reported-by: Aisheng Dong <aisheng.dong@xxxxxxx>
Tested-by: Aisheng Dong <aisheng.dong@xxxxxxx>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
Hello,

Changes since v3 (available at
https://lore.kernel.org/linux-fbdev/20230926150116.2124384-1-u.kleine-koenig@xxxxxxxxxxxxxx):

 - Fix buildfailure identified by the kernel test robot. (*Sigh*, that's
   what you get if you improve a patch without build testing ...)
 - Fix the Subject to also mention "remove".

Best regards
Uwe

 drivers/video/backlight/pwm_bl.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index a51fbab96368..289bd9ce4d36 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -626,9 +626,14 @@ static void pwm_backlight_remove(struct platform_device *pdev)
 {
 	struct backlight_device *bl = platform_get_drvdata(pdev);
 	struct pwm_bl_data *pb = bl_get_data(bl);
+	struct pwm_state state;
 
 	backlight_device_unregister(bl);
 	pwm_backlight_power_off(pb);
+	pwm_get_state(pb->pwm, &state);
+	state.duty_cycle = 0;
+	state.enabled = false;
+	pwm_apply_state(pb->pwm, &state);
 
 	if (pb->exit)
 		pb->exit(&pdev->dev);
@@ -638,8 +643,13 @@ static void pwm_backlight_shutdown(struct platform_device *pdev)
 {
 	struct backlight_device *bl = platform_get_drvdata(pdev);
 	struct pwm_bl_data *pb = bl_get_data(bl);
+	struct pwm_state state;
 
 	pwm_backlight_power_off(pb);
+	pwm_get_state(pb->pwm, &state);
+	state.duty_cycle = 0;
+	state.enabled = false;
+	pwm_apply_state(pb->pwm, &state);
 }
 
 #ifdef CONFIG_PM_SLEEP
@@ -647,12 +657,24 @@ static int pwm_backlight_suspend(struct device *dev)
 {
 	struct backlight_device *bl = dev_get_drvdata(dev);
 	struct pwm_bl_data *pb = bl_get_data(bl);
+	struct pwm_state state;
 
 	if (pb->notify)
 		pb->notify(pb->dev, 0);
 
 	pwm_backlight_power_off(pb);
 
+	/*
+	 * Note that disabling the PWM doesn't guarantee that the output stays
+	 * at its inactive state. However without the PWM disabled, the PWM
+	 * driver refuses to suspend. So disable here even though this might
+	 * enable the backlight on poorly designed boards.
+	 */
+	pwm_get_state(pb->pwm, &state);
+	state.duty_cycle = 0;
+	state.enabled = false;
+	pwm_apply_state(pb->pwm, &state);
+
 	if (pb->notify_after)
 		pb->notify_after(pb->dev, 0);
 

base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
-- 
2.40.1