[PATCH 3/6] drm/vc4: txp: Force alpha to be 0xff if it's disabled

[Maxime Ripard]

If we use a format that has padding instead of the alpha component (such
as XRGB8888), it appears that the Transposer will fill the padding to 0,
disregarding what was stored in the input buffer padding.

This leads to issues with IGT, since it will set the padding to 0xff,
but will then compare the CRC of the two frames which will thus fail.
Another nice side effect is that it is now possible to just use the
buffer as ARGB.

Fixes: 008095e065a8 ("drm/vc4: Add support for the transposer block")
Signed-off-by: Maxime Ripard <maxime at cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_txp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
index ace2d03649ba..5b4dd644214f 100644
--- a/drivers/gpu/drm/vc4/vc4_txp.c
+++ b/drivers/gpu/drm/vc4/vc4_txp.c
@@ -304,6 +304,8 @@ static void vc4_txp_connector_atomic_commit(struct drm_connector *conn,
 
 	if (fb->format->has_alpha)
 		ctrl |= TXP_ALPHA_ENABLE;
+	else
+		ctrl |= TXP_ALPHA_INVERT;
 
 	gem = drm_fb_cma_get_gem_obj(fb, 0);
 	TXP_WRITE(TXP_DST_PTR, gem->paddr + fb->offsets[0]);
-- 
2.35.1