[PATCH AUTOSEL 5.2 02/70] drm/bridge: tc358767: Increase AUX transfer length limit

Sasha Levin sashal at kernel.org
Tue Sep 24 16:44:41 UTC 2019

From: Andrey Smirnov <andrew.smirnov at gmail.com>

[ Upstream commit e0655feaec62d5139b6b13a7b1bbb1ab8f1c2d83 ]

According to the datasheet tc358767 can transfer up to 16 bytes via
its AUX channel, so the artificial limit of 8 appears to be too
low. However only up to 15-bytes seem to be actually supported and
trying to use 16-byte transfers results in transfers failing
sporadically (with bogus status in case of I2C transfers), so limit it
to 15.

Signed-off-by: Andrey Smirnov <andrew.smirnov at gmail.com>
Reviewed-by: Andrzej Hajda <a.hajda at samsung.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
Cc: Andrzej Hajda <a.hajda at samsung.com>
Cc: Laurent Pinchart <Laurent.pinchart at ideasonboard.com>
Cc: Tomi Valkeinen <tomi.valkeinen at ti.com>
Cc: Andrey Gusakov <andrey.gusakov at cogentembedded.com>
Cc: Philipp Zabel <p.zabel at pengutronix.de>
Cc: Cory Tusar <cory.tusar at zii.aero>
Cc: Chris Healy <cphealy at gmail.com>
Cc: Lucas Stach <l.stach at pengutronix.de>
Cc: dri-devel at lists.freedesktop.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Andrzej Hajda <a.hajda at samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190619052716.16831-9-andrew.smirnov@gmail.com
Signed-off-by: Sasha Levin <sashal at kernel.org>
 drivers/gpu/drm/bridge/tc358767.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index f59a51e19dab0..d515c7cebb9c4 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -293,7 +293,7 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
 			       struct drm_dp_aux_msg *msg)
 	struct tc_data *tc = aux_to_tc(aux);
-	size_t size = min_t(size_t, 8, msg->size);
+	size_t size = min_t(size_t, DP_AUX_MAX_PAYLOAD_BYTES - 1, msg->size);
 	u8 request = msg->request & ~DP_AUX_I2C_MOT;
 	u8 *buf = msg->buffer;
 	u32 tmp = 0;

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