Re: [PATCH v5 3/5] drm/dp: Don't read back backlight mode in drm_edp_backlight_enable()

[Doug Anderson]

Hi,

On Fri, Nov 5, 2021 at 11:34 AM Lyude Paul <lyude@xxxxxxxxxx> wrote:
>
> As it turns out, apparently some machines will actually leave additional
> backlight functionality like dynamic backlight control on before the OS
> loads. Currently we don't take care to disable unsupported features when
> writing back the backlight mode, which can lead to some rather strange
> looking behavior when adjusting the backlight.
>
> So, let's fix this by just not reading back the current backlight mode on
> initial enable. I don't think there should really be any downsides to this,
> and this will ensure we don't leave any unsupported functionality enabled.
>
> This should fix at least one (but not all) of the issues seen with DPCD
> backlight support on fi-bdw-samus
>
> v5:
> * Just avoid reading back DPCD register - Doug Anderson
>
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
> Fixes: 867cf9cd73c3 ("drm/dp: Extract i915's eDP backlight code into DRM helpers")
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 40 ++++++++++-----------------------
>  1 file changed, 12 insertions(+), 28 deletions(-)

You forgot to CC me on this one! ;-)

This looks good to me now, so FWIW:

Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>