On Tue, Aug 11, 2020 at 04:26:31PM -0400, Alyssa Rosenzweig wrote:
> The AFBC decoder used in the Rockchip VOP assumes the use of the
> YUV-like colourspace transform (YTR). YTR is lossless for RGB(A)
> buffers, which covers the RGBA8 and RGB565 formats supported in
> vop_convert_afbc_format. Use of YTR is signaled with the
> AFBC_FORMAT_MOD_YTR modifier, which prior to this commit was missing. As
> such, a producer would have to generate buffers that do not use YTR,
> which the VOP would erroneously decode as YTR, leading to severe visual
> corruption.
>
> The upstream AFBC support was developed against a captured frame, which
> failed to exercise modifier support. Prior to bring-up of AFBC in Mesa
> (in the Panfrost driver), no open userspace respected modifier
> reporting. As such, this change is not expected to affect broken
> userspaces.
>
> Tested on RK3399 with Panfrost and Weston.
>
> Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/rockchip/rockchip_drm_vop.h | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> index 4a2099cb5..857d97cdc 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.h
> @@ -17,9 +17,20 @@
>
> #define NUM_YUV2YUV_COEFFICIENTS 12
>
> +/* AFBC supports a number of configurable modes. Relevant to us is block size
> + * (16x16 or 32x8), storage modifiers (SPARSE, SPLIT), and the YUV-like
> + * colourspace transform (YTR). 16x16 SPARSE mode is always used. SPLIT mode
> + * could be enabled via the hreg_block_split register, but is not currently
> + * handled. The colourspace transform is implicitly always assumed by the
> + * decoder, so consumers must use this transform as well.
> + *
> + * Failure to match modifiers will cause errors displaying AFBC buffers
> + * produced by conformant AFBC producers, including Mesa.
> + */
> #define ROCKCHIP_AFBC_MOD \
> DRM_FORMAT_MOD_ARM_AFBC( \
> AFBC_FORMAT_MOD_BLOCK_SIZE_16x16 | AFBC_FORMAT_MOD_SPARSE \
> + | AFBC_FORMAT_MOD_YTR \
> )
>
> enum vop_data_format {
> --
> 2.28.0
>
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
