From c6f93d0184c3928fdc2f28fa7e89f5626595b5f1 Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime@cerno.tech>
Date: Mon, 28 Mar 2022 17:36:56 +0200
Subject: drm/vc4: txp: Force alpha to be 0xff if it's disabled
Git-commit: 5453343a88ede8b12812fced81ecd24cb888ccc3
Patch-mainline: v5.19-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
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
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/vc4/vc4_txp.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
index ace2d03649ba..82beb8c159f2 100644
--- a/drivers/gpu/drm/vc4/vc4_txp.c
+++ b/drivers/gpu/drm/vc4/vc4_txp.c
@@ -304,6 +304,12 @@ 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]);
--
2.38.1