This patch fixes a regression introduced between 2.6.39 & 3.1-rc1
whereby the displayport AUX channel stopped re-trying commands that
elicited a DEFER response.
Signed-off-by: Brad Campbell <brad@xxxxxxxxxxxxxxx>
diff --git a/drivers/gpu/drm/radeon/atombios_dp.c
b/drivers/gpu/drm/radeon/atombios_dp.c
index 7ad43c6..b8450f4 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -60,11 +60,13 @@ static int radeon_process_aux_ch(struct
radeon_i2c_chan *chan,
int index = GetIndexIntoMasterTable(COMMAND,
ProcessAuxChannelTransaction);
unsigned char *base;
int recv_bytes;
+ int retry_count = 0;
memset(&args, 0, sizeof(args));
base = (unsigned char *)rdev->mode_info.atom_context->scratch;
+retry:
memcpy(base, send, send_bytes);
args.v1.lpAuxRequest = 0;
@@ -79,6 +81,16 @@ static int radeon_process_aux_ch(struct
radeon_i2c_chan *chan,
*ack = args.v1.ucReplyStatus;
+ /* defer */
+ if (args.v1.ucReplyStatus == 0x20){
+ DRM_DEBUG_KMS("dp_aux_ch defer\n");
+ /* 10 is an arbitrary value from the pre-regression patch
+ in practice I've never seen more than one */
+ if (retry_count++ < 10)
+ goto retry;
+ return -EBUSY;
+ }
+
/* timeout */
if (args.v1.ucReplyStatus == 1) {
DRM_DEBUG_KMS("dp_aux_ch timeout\n");
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