[PATCH 1/7] drm/msm/dpu: fix the comment on the RGB UBWC plane count

From: Dmitry Baryshkov

Date: Wed Nov 04 2026 - 11:49:07 EST


The comment above the num_planes adjustment for RGB UBWC formats says
that the uAPI leaves plane[1] empty, but the uAPI has nothing to do with
it: an RGB UBWC framebuffer has a single plane, with the metadata in
front of the data. The empty slot is in the DPU layout, which follows
the SSPP SRC0-3 address registers. The RGB metadata is fetched through
SRC2 and SRC1 is not used, so num_planes has to cover slot 2. Say so.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/msm/disp/dpu1/dpu_formats.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_formats.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_formats.c
index 590922c4f69b..a8e9a69834af 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_formats.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_formats.c
@@ -126,7 +126,7 @@ static int _dpu_format_populate_plane_sizes_ubwc(
if (!meta)
return 0;

- /* uAPI leaves plane[1] empty and plane[2] as meta */
+ /* RGB metadata is fetched through SRC2, SRC1 stays unused */
layout->num_planes += 1;

rgb_meta_stride = DIV_ROUND_UP(fb->width, 16);

--
2.47.3