[PATCH] drm/i915/display/dp: On AUX xfer timeout restart freshly

[Arun R Murthy]

On AUX transfer timeout, as per DP spec need to retry for 3 times and
has to be restart freshly.

Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 52 ++++++++++-----------
 1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 0c27db8ae4f1..84d5c936177f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -273,30 +273,6 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 	 * it using the same AUX CH simultaneously
 	 */
 
-	/* Try to wait for any previous AUX channel activity */
-	for (try = 0; try < 3; try++) {
-		status = intel_de_read_notrace(i915, ch_ctl);
-		if ((status & DP_AUX_CH_CTL_SEND_BUSY) == 0)
-			break;
-		msleep(1);
-	}
-	/* just trace the final value */
-	trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
-
-	if (try == 3) {
-		const u32 status = intel_de_read(i915, ch_ctl);
-
-		if (status != intel_dp->aux_busy_last_status) {
-			drm_WARN(&i915->drm, 1,
-				 "%s: not started (status 0x%08x)\n",
-				 intel_dp->aux.name, status);
-			intel_dp->aux_busy_last_status = status;
-		}
-
-		ret = -EBUSY;
-		goto out;
-	}
-
 	/* Only 5 data registers! */
 	if (drm_WARN_ON(&i915->drm, send_bytes > 20 || recv_size > 20)) {
 		ret = -E2BIG;
@@ -304,14 +280,34 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 	}
 
 	while ((aux_clock_divider = intel_dp->get_aux_clock_divider(intel_dp, clock++))) {
-		u32 send_ctl = intel_dp->get_aux_send_ctl(intel_dp,
+		/* Must try at least 3 times according to DP spec */
+		for (try = 0; try < 5; try++) {
+			u32 send_ctl = intel_dp->get_aux_send_ctl(intel_dp,
 							  send_bytes,
 							  aux_clock_divider);
 
-		send_ctl |= aux_send_ctl_flags;
+			send_ctl |= aux_send_ctl_flags;
+
+			/* Try to wait for any previous AUX channel activity */
+			/* TODO: if typeC then 4.2ms else 800us for DG2 ass 1.5ms for both cases */
+			ret = __intel_de_wait_for_register(i915, ch_ctl,
+					   DP_AUX_CH_CTL_SEND_BUSY, 0,
+					   800, 6, &status);
+			/* just trace the final value */
+			trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
+
+			if (ret) {
+				if (status != intel_dp->aux_busy_last_status) {
+					drm_WARN(&i915->drm, 1,
+						 "%s: not started (status 0x%08x)\n",
+						 intel_dp->aux.name, status);
+					intel_dp->aux_busy_last_status = status;
+				}
+
+			ret = -EBUSY;
+			goto out;
+			}
 
-		/* Must try at least 3 times according to DP spec */
-		for (try = 0; try < 5; try++) {
 			/* Load the send data into the aux channel data registers */
 			for (i = 0; i < send_bytes; i += 4)
 				intel_de_write(i915, ch_data[i >> 2],
-- 
2.25.1