Re: [PATCH 2/4] drm/amdgpu/display: don't assert in set backlight function

[Alex Deucher <alexdeucher@gmail.com>]

On Thu, Mar 4, 2021 at 1:33 PM Kazlauskas, Nicholas
<nicholas.kazlauskas@amd.com> wrote:
>
> On 2021-03-04 12:41 p.m., Alex Deucher wrote:
> > It just spams the logs.
> >
> > Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>
> This series in general looks reasonable to me:
> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
>
> > ---
> >   drivers/gpu/drm/amd/display/dc/core/dc_link.c | 1 -
> >   1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> > index fa9a62dc174b..974b70f21837 100644
> > --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> > +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> > @@ -2614,7 +2614,6 @@ bool dc_link_set_backlight_level(const struct dc_link *link,
> >                       if (pipe_ctx->plane_state == NULL)
> >                               frame_ramp = 0;
> >               } else {
> > -                     ASSERT(false);
>
> Just a comment on what's actually going on here with this warning:
>
> Technically we can't apply the backlight level without a plane_state in
> the context but the panel is also off anyway.
>
> I think there might be a bug here when the panel turns on and we're not
> applying values set when it was off but I don't think anyone's reported
> this as an issue.
>
> I'm not entirely sure if the value gets cached and reapplied with the
> correct value later, but it's something to keep in mind.

It doesn't.  I have additional patches here to cache it:
https://cgit.freedesktop.org/~agd5f/linux/log/?h=backlight_wip

Alex

>
> Regards,
> Nicholas Kazlauskas
>
> >                       return false;
> >               }
> >
> >
>
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