[PATCH] drm/amd/display: Reject non-zero src_y and src_x for video planes

[Kazlauskas, Nicholas]

On 2021-04-22 7:20 p.m., Harry Wentland wrote:
> [Why]
> This hasn't been well tested and leads to complete system hangs on DCN1
> based systems, possibly others.
> 
> The system hang can be reproduced by gesturing the video on the YouTube
> Android app on ChromeOS into full screen.
> 
> [How]
> Reject atomic commits with non-zero drm_plane_state.src_x or src_y values.
> 
> Signed-off-by: Harry Wentland <harry.wentland at amd.com>
> Change-Id: I5e951f95fc87c86517b9ea6e094d73603184f00b

Drop the Change-ID on submit.

> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 4b3b9599aaf7..99fd555ebb91 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -2825,6 +2825,13 @@ static int fill_dc_scaling_info(const struct drm_plane_state *state,
>   	scaling_info->src_rect.x = state->src_x >> 16;
>   	scaling_info->src_rect.y = state->src_y >> 16;
>   
> +
> +	if (state->fb &&
> +	    state->fb->format->format == DRM_FORMAT_NV12 &&
> +	    (scaling_info->src_rect.x != 0 ||
> +	     scaling_info->src_rect.y != 0))
> +		return -EINVAL;
> +

Would like to see a comment in the source code similar to what's 
explained in the commit message so if people skim through the code they 
understand some of the background on this.

I'd also like to know if this is generic across all DCN or specific to 
DCN1. For now at least we can disable it generically I think.

With the commit message updated and source commented this patch is:

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>

>   	scaling_info->src_rect.width = state->src_w >> 16;
>   	if (scaling_info->src_rect.width == 0)
>   		return -EINVAL;
>