[Intel-gfx] [PATCHv2] drm/i915/dp: wait on timeout before retry

[Arun R Murthy <arun.r.murthy@intel.com>]

On linktraining error/timeout before retry need to wait for 400usec as
per the DP CTS spec1.2

The patch with commit 74ebf294a1dd ("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.

v2: fixed checkpatch errors and warnings

Signed-off-by: Arun R Murthy <arun.r.murthy@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..3fcff3995009 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