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

[Alex Deucher]

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

> ---
>  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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