[PATCH 2/2] drm/i915/backlight: Make ext_pwm_disable_backlight() call intel_backlight_set_pwm_level()

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Sun, 2021-11-21 at 12:00 +0100, Hans de Goede 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 at redhat.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);
>  }

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat