[Intel-gfx] [PATCH] drm/i915/dp: wait on timeout before retry

[Arun R Murthy]

On linktraining error/timeout before retry need to wait for 400usec as
per the DP CTS spec1.2
The patch with commit id
74ebf294a1dd816bdc248ac733009a8915d59eb5
drm/i915: Add a delay in Displayport AUX transactions for
compliance testing
removes this delay mentioning the hardware already meets this
requirement, but as per the spec the delay mentioned in the spec
specifies how long to wait for the receiver response before timeout. So
the delay here to wait for timeout and not a delay after timeout. The DP
spec specifies a delay after timeout and hence adding this delay.

Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 2bc119374555..a1fef1645d6a 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -286,13 +286,9 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 			/*
 			 * DP CTS 1.2 Core Rev 1.1, 4.2.1.1 & 4.2.1.2
 			 *   400us delay required for errors and timeouts
-			 *   Timeout errors from the HW already meet this
-			 *   requirement so skip to next iteration
 			 */
-			if (status & DP_AUX_CH_CTL_TIME_OUT_ERROR)
-				continue;
-
-			if (status & DP_AUX_CH_CTL_RECEIVE_ERROR) {
+			if (status & (DP_AUX_CH_CTL_RECEIVE_ERROR |
+						DP_AUX_CH_CTL_TIME_OUT_ERROR)) {
 				usleep_range(400, 500);
 				continue;
 			}
-- 
2.25.1