[PATCH] drm: Check actual format for legacy pageflip.

[Mario Kleiner]

On Thu, Jan 7, 2021 at 6:57 PM Daniel Vetter <daniel at ffwll.ch> wrote:

> On Sat, Jan 02, 2021 at 04:31:36PM +0100, Mario Kleiner wrote:
> > On Sat, Jan 2, 2021 at 3:02 PM Bas Nieuwenhuizen
> > <bas at basnieuwenhuizen.nl> wrote:
> > >
> > > With modifiers one can actually have different format_info structs
> > > for the same format, which now matters for AMDGPU since we convert
> > > implicit modifiers to explicit modifiers with multiple planes.
> > >
> > > I checked other drivers and it doesn't look like they end up triggering
> > > this case so I think this is safe to relax.
> > >
> > > Signed-off-by: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
> > > Fixes: 816853f9dc40 ("drm/amd/display: Set new format info for
> converted metadata.")
> > > ---
> > >  drivers/gpu/drm/drm_plane.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> > > index e6231947f987..f5085990cfac 100644
> > > --- a/drivers/gpu/drm/drm_plane.c
> > > +++ b/drivers/gpu/drm/drm_plane.c
> > > @@ -1163,7 +1163,7 @@ int drm_mode_page_flip_ioctl(struct drm_device
> *dev,
> > >         if (ret)
> > >                 goto out;
> > >
> > > -       if (old_fb->format != fb->format) {
> > > +       if (old_fb->format->format != fb->format->format) {
> >
> > This was btw. the original way before Ville made it more strict about
> > 4 years ago, to catch issues related to tiling, and more complex
> > layouts, like the dcc tiling/retiling introduced by your modifier
> > patches. That's why I hope my alternative patch is a good solution for
> > atomic drivers while keeping the strictness for potential legacy
> > drivers.
>
> Yeah this doesn't work in full generality, because hw might need to do a
> full modeset to do a full modeset to reallocate resources (like scanout
> fifo space) if the format changes.
>
> But for atomic drivers that should be caught in ->atomic_check, which
> should result in -EINVAL, so should do the right thing. So it should be
> all good, but imo needs a comment to explain what's going on:
>
>         /*
>          * Only check the FOURCC format code, excluding modifiers. This is
>          * enough for all legacy drivers. Atomic drivers have their own
>          * checks in their ->atomic_check implementation, which will
>          * return -EINVAL if any hw or driver constraint is violated due
>          * to modifier changes.
>          */
>
> Also can you pls cc: intel-gfx to get this vetted by the intel-gfx ci?
>
> With that:
>
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
>
Ah, my "atomic expert", posting simultaneously with myself :). Happy new
year. Opinions on my variant, just replied a minute ago?

thanks,
-mario

>
> > -mario
> >
> > >                 DRM_DEBUG_KMS("Page flip is not allowed to change
> frame buffer format.\n");
> > >                 ret = -EINVAL;
> > >                 goto out;
> > > --
> > > 2.29.2
> > >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
>
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