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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Philipp Zabel <p.zabel@pengutronix.de>,
        Andrey Gusakov <andrey.gusakov@cogentembedded.com>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.9 58/86] drm/bridge: tc358767: fix AUXDATAn registers access
Date:   Fri,  2 Feb 2018 17:58:18 +0100
Message-Id: <20180202140827.826456609@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrey Gusakov <andrey.gusakov@cogentembedded.com>


[ Upstream commit 9217c1abbc145a77d65c476cf2004a3df02104c7 ]

First four bytes should go to DP0_AUXWDATA0. Due to bug if
len > 4 first four bytes was writen to DP0_AUXWDATA1 and all
data get shifted by 4 bytes. Fix it.

Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Andrey Gusakov <andrey.gusakov@cogentembedded.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1510073785-16108-6-git-send-email-andrey.gusakov@cogentembedded.com
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/bridge/tc358767.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -318,7 +318,7 @@ static ssize_t tc_aux_transfer(struct dr
 				tmp = (tmp << 8) | buf[i];
 			i++;
 			if (((i % 4) == 0) || (i == size)) {
-				tc_write(DP0_AUXWDATA(i >> 2), tmp);
+				tc_write(DP0_AUXWDATA((i - 1) >> 2), tmp);
 				tmp = 0;
 			}
 		}