From dec9ced122899372a8baf20291e5f0abf5314f47 Mon Sep 17 00:00:00 2001
From: Paul Cercueil <paul@crapouillou.net>
Date: Fri, 3 Jul 2020 16:13:41 +0200
Subject: drm/dbi: Fix SPI Type 1 (9-bit) transfer
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Git-commit: 900ab59e2621053b009f707f80b2c19ce0af5dee
Patch-mainline: v5.8
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322

The function mipi_dbi_spi1_transfer() will transfer its payload as 9-bit
data, the 9th (MSB) bit being the data/command bit. In order to do that,
it unpacks the 8-bit values into 16-bit values, then sets the 9th bit if
the byte corresponds to data, clears it otherwise. The 7 MSB are
padding. The array of now 16-bit values is then passed to the SPI core
for transfer.

This function was broken since its introduction, as the length of the
SPI transfer was set to the payload size before its conversion, but the
payload doubled in size due to the 8-bit -> 16-bit conversion.

Fixes: 02dd95fe3169 ("drm/tinydrm: Add MIPI DBI support")
Cc: <stable@vger.kernel.org> # 5.4+
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200703141341.1266263-1-paul@crapouillou.net
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/drm_mipi_dbi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
index bb27c82757f1..bf7888ad9ad4 100644
--- a/drivers/gpu/drm/drm_mipi_dbi.c
+++ b/drivers/gpu/drm/drm_mipi_dbi.c
@@ -923,7 +923,7 @@ static int mipi_dbi_spi1_transfer(struct mipi_dbi *dbi, int dc,
 			}
 		}
 
-		tr.len = chunk;
+		tr.len = chunk * 2;
 		len -= chunk;
 
 		ret = spi_sync(spi, &m);
-- 
2.28.0