Re: [PATCH 1/3] drm/vc4: Set PPF scaling when the source image is only vertically scaled

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Wed, 24 Oct 2018 12:05:03 +0200
Boris Brezillon <boris.brezillon@bootlin.com> wrote:

> The source image might be only vertically scaled, and in this case
> ->is_unity will be false, but we'd still have to force ->x_scaling[0]  
> to VC4_SCALING_PPF for YUV conversion to work properly.
> 
> Let's replace the ->is_unity test by->x_scaling[0] == VC4_SCALING_NONE
> to cope with that.
> 
> Fixes: 658d8cbd07da ("drm/vc4: Fix the "no scaling" case on multi-planar YUV formats")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
> ---
>  drivers/gpu/drm/vc4/vc4_plane.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
> index 60d5ad19cedd..32b7b9f47c5d 100644
> --- a/drivers/gpu/drm/vc4/vc4_plane.c
> +++ b/drivers/gpu/drm/vc4/vc4_plane.c
> @@ -318,7 +318,7 @@ static int vc4_plane_setup_clipping_and_scaling(struct drm_plane_state *state)
>  		 * even on a plane that's otherwise 1:1. Looks like only PPF
>  		 * works in that case, so let's pick that one.
>  		 */
> -		if (vc4_state->is_unity)
> +		if (vc4_state->x_scaling[0] == VC4_SCALING_NONE)
>  			vc4_state->x_scaling[0] = VC4_SCALING_PPF;

Actually, I'm not sure about this patch is needed. According to the
spec, we should not enable the scaler on the Y channel when ->is_unity
is true.
I tested it, and it seems to work if we just leave x_scaling[0] to
VC4_SCALING_NONE.

Eric, do you remember why you did that?