linux-kernel - [PATCH 5.17 249/772] drm/vc4: txp: Dont set TXP_VSTART_AT

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Message-Id: <20220607164956.364650024@linuxfoundation.org>
Date:   Tue,  7 Jun 2022 18:57:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Maxime Ripard <maxime@...no.tech>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 249/772] drm/vc4: txp: Dont set TXP_VSTART_AT_EOF

From: Maxime Ripard <maxime@...no.tech>

[ Upstream commit 234998df929f14d00cbf2f1e81a7facb69fd9266 ]

The TXP_VSTART_AT_EOF will generate a second VSTART signal to the HVS.
However, the HVS waits for VSTART to enable the FIFO and will thus start
filling the FIFO before the start of the frame.

This leads to corruption at the beginning of the first frame, and
content from the previous frame at the beginning of the next frames.

Since one VSTART is enough, let's get rid of it.

Fixes: 008095e065a8 ("drm/vc4: Add support for the transposer block")
Signed-off-by: Maxime Ripard <maxime@...no.tech>
Acked-by: Thomas Zimmermann <tzimmermann@...e.de>
Link: https://lore.kernel.org/r/20220328153659.2382206-3-maxime@cerno.tech
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/vc4/vc4_txp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
index 9809ca3e2945..ace2d03649ba 100644
--- a/drivers/gpu/drm/vc4/vc4_txp.c
+++ b/drivers/gpu/drm/vc4/vc4_txp.c
@@ -298,7 +298,7 @@ static void vc4_txp_connector_atomic_commit(struct drm_connector *conn,
 	if (WARN_ON(i == ARRAY_SIZE(drm_fmts)))
 		return;
 
-	ctrl = TXP_GO | TXP_VSTART_AT_EOF | TXP_EI |
+	ctrl = TXP_GO | TXP_EI |
 	       VC4_SET_FIELD(0xf, TXP_BYTE_ENABLE) |
 	       VC4_SET_FIELD(txp_fmts[i], TXP_FORMAT);
 
-- 
2.35.1