[PATCH] drm/radeon/kms: retry aux transactions if there are status flags

[alexdeucher at gmail.com]

From: Alex Deucher <alexander.deucher at amd.com>

If there are error flags in the aux status, retry the transaction.
This makes aux much more reliable, especially on llano systems.

Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
Cc: stable at kernel.org
---
 drivers/gpu/drm/radeon/atombios_dp.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
index 4da2388..79e8ebc 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -129,7 +129,9 @@ static int radeon_dp_aux_native_write(struct radeon_connector *radeon_connector,
 	for (retry = 0; retry < 4; retry++) {
 		ret = radeon_process_aux_ch(dig_connector->dp_i2c_bus,
 					    msg, msg_bytes, NULL, 0, delay, &ack);
-		if (ret < 0)
+		if (ret == -EBUSY)
+			continue;
+		else if (ret < 0)
 			return ret;
 		if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK)
 			return send_bytes;
@@ -160,7 +162,9 @@ static int radeon_dp_aux_native_read(struct radeon_connector *radeon_connector,
 	for (retry = 0; retry < 4; retry++) {
 		ret = radeon_process_aux_ch(dig_connector->dp_i2c_bus,
 					    msg, msg_bytes, recv, recv_bytes, delay, &ack);
-		if (ret < 0)
+		if (ret == -EBUSY)
+			continue;
+		else if (ret < 0)
 			return ret;
 		if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK)
 			return ret;
@@ -236,7 +240,9 @@ int radeon_dp_i2c_aux_ch(struct i2c_adapter *adapter, int mode,
 	for (retry = 0; retry < 4; retry++) {
 		ret = radeon_process_aux_ch(auxch,
 					    msg, msg_bytes, reply, reply_bytes, 0, &ack);
-		if (ret < 0) {
+		if (ret == -EBUSY)
+			continue;
+		else if (ret < 0) {
 			DRM_DEBUG_KMS("aux_ch failed %d\n", ret);
 			return ret;
 		}
-- 
1.7.1.1