Re: [Intel-gfx] [PATCH 2/2] drm/i915/backlight: Make ext_pwm_disable_backlight() call intel_backlight_set_pwm_level()

[Jani Nikula <jani.nikula@linux.intel.com>]

On Sun, 21 Nov 2021, Hans de Goede <hdegoede@redhat.com> 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@redhat.com>

I'll take your word for it.

Acked-by: Jani Nikula <jani.nikula@intel.com>


> ---
>  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