[PATCH v2 2/2] drm/vc4: Prefer PPF over TPZ when dst >= 2/3 src

[Boris Brezillon <boris.brezillon@xxxxxxxxxxx>]

The HVS spec recommends using PPF when the downscaling ratio is
between 2/3 and 1. Let's modify vc4_get_scaling_mode() to follow this
recommendation.

Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
Reviewed-by: Eric Anholt <eric@xxxxxxxxxx>
---
Changes in v2:
- Add Eric's R-b
---
 drivers/gpu/drm/vc4/vc4_plane.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index 6caa678edcff..1728fb7d00ba 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -129,12 +129,12 @@ static const struct hvs_format *vc4_get_hvs_format(u32 drm_format)
 
 static enum vc4_scaling_mode vc4_get_scaling_mode(u32 src, u32 dst)
 {
-	if (dst > src)
+	if (dst == src)
+		return VC4_SCALING_NONE;
+	if (3 * dst >= 2 * src)
 		return VC4_SCALING_PPF;
-	else if (dst < src)
-		return VC4_SCALING_TPZ;
 	else
-		return VC4_SCALING_NONE;
+		return VC4_SCALING_TPZ;
 }
 
 static bool plane_enabled(struct drm_plane_state *state)
-- 
2.17.1

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