On Sun, 21 Nov 2021, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > At least the Bay Trail LPSS PWM controller used with DSI panels on many > Bay Trail tablets seems to leave the PWM pin in whatever state it was > (high or low) ATM that the PWM gets disabled. Combined with some panels > not having a separate backlight-enable pin this leads to the backlight > sometimes staying on while it should not (when the pin was high during > PWM-disabling). > > First calling intel_backlight_set_pwm_level() will ensure that the pin > is always low (or high for inverted brightness panels) since the passed > in duty-cycle is 0% (or 100%) when the PWM gets disabled fixing the > backlight sometimes staying on. > > With the exception of ext_pwm_disable_backlight() all other > foo_disable_backlight() functions call intel_backlight_set_pwm_level() > already before disabling the backlight, so this change also aligns > ext_pwm_disable_backlight() with all the other disable() functions. > > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> I'll take your word for it. Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx> > --- > drivers/gpu/drm/i915/display/intel_backlight.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c > index 03cd730c926a..2758a2f6c093 100644 > --- a/drivers/gpu/drm/i915/display/intel_backlight.c > +++ b/drivers/gpu/drm/i915/display/intel_backlight.c > @@ -421,6 +421,8 @@ static void ext_pwm_disable_backlight(const struct drm_connector_state *old_conn > struct intel_connector *connector = to_intel_connector(old_conn_state->connector); > struct intel_panel *panel = &connector->panel; > > + intel_backlight_set_pwm_level(old_conn_state, level); > + > panel->backlight.pwm_state.enabled = false; > pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state); > } -- Jani Nikula, Intel Open Source Graphics Center
