[PATCH] drm/amd/display: Fix 10bit 4K display on CIK GPUs

[Alex Deucher]

Applied.  Thanks!

Alex

On Thu, Jul 15, 2021 at 3:40 PM Harry Wentland <harry.wentland at amd.com> wrote:
>
>
>
> On 2021-07-15 3:19 p.m., Mario Kleiner wrote:
> > On Thu, Jul 15, 2021 at 6:10 PM Alex Deucher <alexdeucher at gmail.com> wrote:
> >>
> >> On Wed, Jul 14, 2021 at 4:15 AM Liviu Dudau <liviu at dudau.co.uk> wrote:
> >>>
> >>> Commit 72a7cf0aec0c ("drm/amd/display: Keep linebuffer pixel depth at
> >>> 30bpp for DCE-11.0.") doesn't seems to have fixed 10bit 4K rendering over
> >>> DisplayPort for CIK GPUs. On my machine with a HAWAII GPU I get a broken
> >>> image that looks like it has an effective resolution of 1920x1080 but
> >>> scaled up in an irregular way. Reverting the commit or applying this
> >>> patch fixes the problem on v5.14-rc1.
> >>>
> >>> Fixes: 72a7cf0aec0c ("drm/amd/display: Keep linebuffer pixel depth at 30bpp for DCE-11.0.")
> >>> Signed-off-by: Liviu Dudau <liviu at dudau.co.uk>
> >>
> >> Harry or Mario any ideas?  Maybe we need finer grained DCE version
> >> checking?  I don't remember all of the caveats of this stuff.  DCE11
> >> and older is getting to be pretty old at this point.  I can just apply
> >> this if you don't have any insights.
> >>
> >> Alex
> >>
> >
> > Hi Alex
> >
> > I'd be fine with applying this. As my original commit says, photometer
> > measurements showed that increasing the line buffer depth was only
> > needed for my DCN-1 RavenRidge, not for my DCE-11.2 Polaris11 or a
> > DCE-8.3 cik, so this should probably not cause harm to the increased
> > precision modes.
> >
> > Note that given the hardware and USB-C/DP-HDMI adapters i have, I only
> > tested this on a 2560x1440 at 144 Hz DP monitor with DCN-1, DCE-11.2, and
> > a 2560x1440 at 100 Hz HDMI monitor iirc with DCN-1, DCE-8.3, and i think
> > on a 2880x1800 at 60 Hz MBP Retina eDP panel with DCE-11.2. These are the
> > highest resolution/framerate monitors I have atm.I don't have access
> > to any 4k monitors, so maybe the problem is somehow specific to such
> > high resolutions? Maybe somewhere else in the code something would
> > need to be adapted? Lacking actual hw docs, my coding here is by
> > pattern matching against existing DC code, guessing and testing on my
> > limited hw samples.
> >
> > Acked-by: Mario Kleiner <mario.kleiner.de at gmail.com>
>
> Makes sense.
>
> Reviewed-by: Harry Wentland <harry.wentland at amd.com>
>
> Harry
>
> >
> > -mario
> >
> >>> ---
> >>>  drivers/gpu/drm/amd/display/dc/core/dc_resource.c | 2 +-
> >>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> >>> index a6a67244a322e..1596f6b7fed7c 100644
> >>> --- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> >>> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> >>> @@ -1062,7 +1062,7 @@ bool resource_build_scaling_params(struct pipe_ctx *pipe_ctx)
> >>>          * so use only 30 bpp on DCE_VERSION_11_0. Testing with DCE 11.2 and 8.3
> >>>          * did not show such problems, so this seems to be the exception.
> >>>          */
> >>> -       if (plane_state->ctx->dce_version != DCE_VERSION_11_0)
> >>> +       if (plane_state->ctx->dce_version > DCE_VERSION_11_0)
> >>>                 pipe_ctx->plane_res.scl_data.lb_params.depth = LB_PIXEL_DEPTH_36BPP;
> >>>         else
> >>>                 pipe_ctx->plane_res.scl_data.lb_params.depth = LB_PIXEL_DEPTH_30BPP;
> >>> --
> >>> 2.32.0
> >>>
> >>> _______________________________________________
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> >>> amd-gfx at lists.freedesktop.org
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