@@ -877,9 +877,19 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
DP_AUX_CH_CTL_TIME_OUT_ERROR |
DP_AUX_CH_CTL_RECEIVE_ERROR);
- if (status & (DP_AUX_CH_CTL_TIME_OUT_ERROR |
- DP_AUX_CH_CTL_RECEIVE_ERROR))
+ if (status & DP_AUX_CH_CTL_TIME_OUT_ERROR) {
+ DRM_DEBUG_DRIVER("HW timeout detected on AUX transaction\n");
+ }
+
+ /* 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_RECEIVE_ERROR) {
+ usleep_range(400, 500);
continue;
+ }
if (status & DP_AUX_CH_CTL_DONE)
break;
}
The Displayport Link Layer Compliance Testing Specification 1.2 rev 1.1 specifies that repeated AUX transactions after a failure (no response / invalid response) must have a minimum delay of 400us before the resend can occur. Tests 4.2.1.1 and 4.2.1.2 are two tests that require this specifically. Also, the check for DP_AUX_CH_CTL_TIME_OUT_ERROR has been moved out into a separate case. As of now, the only action taken is to log the error, since the HW will have already waited the required amount of time for the transaction to complete. V2: - Changed udelay() to usleep_range() V3: - Removed extraneous check for timeout - Updated comment to reflect this change V4: - Reformatted a comment V5: - Added separate check for HW timeout on AUX transactions. A message is logged upon detection of this case. Signed-off-by: Todd Previte <tprevite@gmail.com> --- drivers/gpu/drm/i915/intel_dp.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)