Currently when calling pwm_apply_might_sleep in the probe routine
the pwm will be configured with an not fully defined state.
The duty_cycle is not yet set in that moment. There is a final
backlight_update_status call that will have a properly setup state.
However this change in the backlight can create a short flicker if the
backlight was already preinitialised.
We fix the flicker by moving the pwm_apply after the default duty_cycle
can be calculated.
Signed-off-by: Michael Grzeschik <m.grzesc...@pengutronix.de>
---
drivers/video/backlight/pwm_bl.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 237d3d3f3bb1a..5924e0b9f01e7 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -518,13 +518,6 @@ static int pwm_backlight_probe(struct platform_device
*pdev)
if (!state.period && (data->pwm_period_ns > 0))
state.period = data->pwm_period_ns;
- ret = pwm_apply_might_sleep(pb->pwm, &state);
- if (ret) {
- dev_err_probe(&pdev->dev, ret,
- "failed to apply initial PWM state");
- goto err_alloc;
- }
-
memset(&props, 0, sizeof(struct backlight_properties));
if (data->levels) {
@@ -582,6 +575,15 @@ static int pwm_backlight_probe(struct platform_device
*pdev)
pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
pb->scale));
+ state.duty_cycle = compute_duty_cycle(pb, data->dft_brightness, &state);
+
+ ret = pwm_apply_might_sleep(pb->pwm, &state);
+ if (ret) {
+ dev_err_probe(&pdev->dev, ret,
+ "failed to apply initial PWM state");
+ goto err_alloc;
+ }
+
props.type = BACKLIGHT_RAW;
props.max_brightness = data->max_brightness;
bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
---
base-commit: 739a6c93cc755c0daf3a7e57e018a8c61047cd90
change-id: 20250731-blpwm-598ecad93c4d
Best regards,
--
Michael Grzeschik <m.grzesc...@pengutronix.de>
