On Fri, 9 Nov 2018 11:26:32 +0100
Boris Brezillon <boris.brezillon@xxxxxxxxxxx> wrote:
> For the YUV conversion to work properly, ->x_scaling[1] should never
> be set to VC4_SCALING_NONE, but vc4_get_scaling_mode() might return
> VC4_SCALING_NONE if the horizontal scaling ratio exactly matches the
> horizontal subsampling factor. Add a test to turn VC4_SCALING_NONE
> into VC4_SCALING_PPF when that happens.
>
> The old ->x_scaling[0] adjustment is dropped as I couldn't find any
> mention to this constraint in the spec and it's proven to be
> unnecessary (I tested various multi-planar YUV formats with scaling
> disabled, and all of them worked fine without this adjustment).
>
> Fixes: fc04023fafec ("drm/vc4: Add support for YUV planes.")
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
> Reviewed-by: Eric Anholt <eric@xxxxxxxxxx>
Series queued to drm-misc-next.
> ---
> Changes in v2:
> - Remove the the ->x_scaling[0] = VC4_SCALING_PPF
> assignment when ->is_unity is true and update the comment
> - Add Eric's R-b
> ---
> drivers/gpu/drm/vc4/vc4_plane.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
> index 98fae4daa08c..6caa678edcff 100644
> --- a/drivers/gpu/drm/vc4/vc4_plane.c
> +++ b/drivers/gpu/drm/vc4/vc4_plane.c
> @@ -341,12 +341,14 @@ static int vc4_plane_setup_clipping_and_scaling(struct drm_plane_state *state)
> vc4_get_scaling_mode(vc4_state->src_h[1],
> vc4_state->crtc_h);
>
> - /* YUV conversion requires that horizontal scaling be enabled,
> - * even on a plane that's otherwise 1:1. Looks like only PPF
> - * works in that case, so let's pick that one.
> + /* YUV conversion requires that horizontal scaling be enabled
> + * on the UV plane even if vc4_get_scaling_mode() returned
> + * VC4_SCALING_NONE (which can happen when the down-scaling
> + * ratio is 0.5). Let's force it to VC4_SCALING_PPF in this
> + * case.
> */
> - if (vc4_state->is_unity)
> - vc4_state->x_scaling[0] = VC4_SCALING_PPF;
> + if (vc4_state->x_scaling[1] == VC4_SCALING_NONE)
> + vc4_state->x_scaling[1] = VC4_SCALING_PPF;
> } else {
> vc4_state->is_yuv = false;
> vc4_state->x_scaling[1] = VC4_SCALING_NONE;
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