Re: [PATCH 03/10] drm/sun4i: Don't pretend to handle ARGB8888 with the frontend

[Chen-Yu Tsai <wens@csie.org>]

On Thu, Mar 22, 2018 at 4:23 PM, Paul Kocialkowski
<paul.kocialkowski@bootlin.com> wrote:
> Hi Chen-Yu,
>
> On Thu, 2018-03-22 at 14:47 +0800, Chen-Yu Tsai wrote:
>> On Wed, Mar 21, 2018 at 11:28 PM, Paul Kocialkowski
>> <paul.kocialkowski@bootlin.com> wrote:
>> > It turns out that the frontend is not capable of preserving the
>> > alpha
>> > component (that is always set to 0xff), so only support XRGB8888
>> > instead.
>> >
>> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
>> > ---
>> >  drivers/gpu/drm/sun4i/sun4i_backend.c  | 4 ++++
>> >  drivers/gpu/drm/sun4i/sun4i_frontend.c | 3 +--
>> >  drivers/gpu/drm/sun4i/sun4i_layer.c    | 4 ++--
>> >  3 files changed, 7 insertions(+), 4 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c
>> > b/drivers/gpu/drm/sun4i/sun4i_backend.c
>> > index b98dafda52f8..274a1db6fa8e 100644
>> > --- a/drivers/gpu/drm/sun4i/sun4i_backend.c
>> > +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
>> > @@ -440,6 +440,10 @@ static bool
>> > sun4i_backend_plane_uses_frontend(struct drm_plane_state *state)
>> >         if (IS_ERR(backend->frontend))
>> >                 return false;
>> >
>> > +       /*
>> > +        * TODO: Don't use the frontend for x2/x4 scaling and allow
>> > RGB formats
>> > +        * with an alpha component then.
>>
>> This and the commit log are kind of conflicting. Is it just the scalar
>> that doesn't
>> work with an alpha component, or the whole frontend?
>
> It's the whole frontend that does not support alpha in its output
> formats. I'm talking about scaling here because that's still the main
> reason to use the frontend. On the other hand, the backend allows
> integer scaling with an alpha component, hence the comment.

I see. I parsed the TODO note incorrectly.

> Do you think I need to rework the comment/commit log?

I think

    Allow integer scaling with alpha using just the backend.

would be slightly clearer.

Thanks
ChenYu

> Thanks for the review,
>
> Paul
>
>> > +        */
>> >         return sun4i_backend_plane_uses_scaler(state);
>> >  }
>> >
>> > diff --git a/drivers/gpu/drm/sun4i/sun4i_frontend.c
>> > b/drivers/gpu/drm/sun4i/sun4i_frontend.c
>> > index ddf6cfa6dd23..3ea925584891 100644
>> > --- a/drivers/gpu/drm/sun4i/sun4i_frontend.c
>> > +++ b/drivers/gpu/drm/sun4i/sun4i_frontend.c
>> > @@ -107,7 +107,7 @@ EXPORT_SYMBOL(sun4i_frontend_update_buffer);
>> >  static int sun4i_frontend_drm_format_to_input_fmt(uint32_t fmt, u32
>> > *val)
>> >  {
>> >         switch (fmt) {
>> > -       case DRM_FORMAT_ARGB8888:
>> > +       case DRM_FORMAT_XRGB8888:
>> >                 *val = 5;
>> >                 return 0;
>> >
>> > @@ -120,7 +120,6 @@ static int
>> > sun4i_frontend_drm_format_to_output_fmt(uint32_t fmt, u32 *val)
>> >  {
>> >         switch (fmt) {
>> >         case DRM_FORMAT_XRGB8888:
>> > -       case DRM_FORMAT_ARGB8888:
>> >                 *val = 2;
>> >                 return 0;
>> >
>> > diff --git a/drivers/gpu/drm/sun4i/sun4i_layer.c
>> > b/drivers/gpu/drm/sun4i/sun4i_layer.c
>> > index eb93df445a10..15238211a61a 100644
>> > --- a/drivers/gpu/drm/sun4i/sun4i_layer.c
>> > +++ b/drivers/gpu/drm/sun4i/sun4i_layer.c
>> > @@ -100,9 +100,9 @@ static void
>> > sun4i_backend_layer_atomic_update(struct drm_plane *plane,
>> >                 sun4i_frontend_update_coord(frontend, plane);
>> >                 sun4i_frontend_update_buffer(frontend, plane);
>> >                 sun4i_frontend_update_formats(frontend, plane,
>> > -                                             DRM_FORMAT_ARGB8888);
>> > +                                             DRM_FORMAT_XRGB8888);
>> >                 sun4i_backend_update_layer_frontend(backend, layer-
>> > >id, plane,
>> > -                                                   DRM_FORMAT_ARGB8
>> > 888);
>> > +                                                   DRM_FORMAT_XRGB8
>> > 888);
>> >                 sun4i_frontend_enable(frontend);
>> >         } else {
>> >                 sun4i_backend_update_layer_formats(backend, layer-
>> > >id, plane);
>> > --
>> > 2.16.2
>> >
>>
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> --
> Paul Kocialkowski, Bootlin (formerly Free Electrons)
> Embedded Linux and kernel engineering
> https://bootlin.com