drm/vc4: txp: Force alpha to be 0xff if it's disabled

[ Upstream commit 5453343a88ede8b12812fced81ecd24cb888ccc3 ]

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@cerno.tech>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20220328153659.2382206-4-maxime@cerno.tech
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
index d4e750cf3c0281d5ccdeda84f1318b7f3f6016ff..f8fa09dfea5da48c393559b609278cadb86b40b1 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_txp.c
+++ b/drivers/gpu/drm/vc4/vc4_txp.c
@@ -301,6 +301,12 @@ static void vc4_txp_connector_atomic_commit(struct drm_connector *conn,
 
        if (fb->format->has_alpha)
                ctrl |= TXP_ALPHA_ENABLE;
+       else
+               /*
+                * If TXP_ALPHA_ENABLE isn't set and TXP_ALPHA_INVERT is, the
+                * hardware will force the output padding to be 0xff.
+                */
+               ctrl |= TXP_ALPHA_INVERT;
 
        gem = drm_fb_cma_get_gem_obj(fb, 0);
        TXP_WRITE(TXP_DST_PTR, gem->paddr + fb->offsets[0]);