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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Thu, 15 Jul 2021 12:10:01 -0400
Message-ID: <CADnq5_OA-em2jM-vmwaM7xxycOS-18EPC0r_myb7REy9b4h_vA@mail.gmail.com>
Subject: Re: [PATCH] drm/amd/display: Fix 10bit 4K display on CIK GPUs
To:     Liviu Dudau <liviu@dudau.co.uk>
Cc:     Harry Wentland <harry.wentland@amd.com>,
        Mario Kleiner <mario.kleiner.de@gmail.com>,
        Leo Li <sunpeng.li@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        LKML <linux-kernel@vger.kernel.org>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
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On Wed, Jul 14, 2021 at 4:15 AM Liviu Dudau <liviu@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@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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