linux-kernel - [PATCH AUTOSEL 6.5 03/36] drm: bridge: samsung-dsim: Drain command transfer FIFO before transfer

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Message-Id: <20230908192848.3462476-3-sashal@kernel.org>
Date:   Fri,  8 Sep 2023 15:28:14 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Marek Vasut <marex@...x.de>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Sasha Levin <sashal@...nel.org>, inki.dae@...sung.com,
        m.szyprowski@...sung.com, andrzej.hajda@...el.com,
        neil.armstrong@...aro.org, rfoss@...nel.org, airlied@...il.com,
        daniel@...ll.ch, dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.5 03/36] drm: bridge: samsung-dsim: Drain command transfer FIFO before transfer

From: Marek Vasut <marex@...x.de>

[ Upstream commit 14806c6415820b1c4bc317655c40784d050a2edb ]

Wait until the command transfer FIFO is empty before loading in the next
command. The previous behavior where the code waited until command transfer
FIFO was not full suffered from transfer corruption, where the last command
in the FIFO could be overwritten in case the FIFO indicates not full, but
also does not have enough space to store another transfer yet.

Signed-off-by: Marek Vasut <marex@...x.de>
Reviewed-by: Jagan Teki <jagan@...rulasolutions.com>
Tested-by: Jagan Teki <jagan@...rulasolutions.com> # imx8mm-icore
Link: https://patchwork.freedesktop.org/patch/msgid/20230615201511.565923-1-marex@denx.de
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 73ec60757dbcb..9e253af69c7a1 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1009,7 +1009,7 @@ static int samsung_dsim_wait_for_hdr_fifo(struct samsung_dsim *dsi)
 	do {
 		u32 reg = samsung_dsim_read(dsi, DSIM_FIFOCTRL_REG);
 
-		if (!(reg & DSIM_SFR_HEADER_FULL))
+		if (reg & DSIM_SFR_HEADER_EMPTY)
 			return 0;
 
 		if (!cond_resched())
-- 
2.40.1