Radeon regression fix

[Brad Campbell]

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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