[PATCH v3] drm/i915/dp: Clean up intel_dp_check_mst_status

[Dhinakaran Pandiyan]

Rewriting this code without the goto, I believe, makes it more readable.
One functional change that has been included is the handling of failed ESI
register reads. Instead of disabling MST only for the first failed read, we
now disable MST on subsequent failed reads too. A failed ESI read is
problematic irrespective of whether it is the first or not.

v2: Don't ignore return from _mst_hpd_irq() (James)
v3: Rebased.

Cc: James Ausmus <james.ausmus at intel.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
Reviewed-by: James Ausmus <james.ausmus at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 78 ++++++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 44 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index aa75f55eeb61..1701ee57ea4f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4196,57 +4196,47 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 static int
 intel_dp_check_mst_status(struct intel_dp *intel_dp)
 {
-	bool bret;
+	u8 esi[DP_DPRX_ESI_LEN] = { 0 };
+	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
 
-	if (intel_dp->is_mst) {
-		u8 esi[DP_DPRX_ESI_LEN] = { 0 };
-		int ret = 0;
-		int retry;
+	if (!intel_dp->is_mst)
+		return -EINVAL;
+
+	while (intel_dp_get_sink_irq_esi(intel_dp, esi)) {
+		int ret, retry;
 		bool handled;
-		bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
-go_again:
-		if (bret == true) {
-
-			/* check link status - esi[10] = 0x200c */
-			if (intel_dp->active_mst_links &&
-			    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
-				DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
-				intel_dp_start_link_train(intel_dp);
-				intel_dp_stop_link_train(intel_dp);
-			}
 
-			DRM_DEBUG_KMS("got esi %3ph\n", esi);
-			ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
-
-			if (handled) {
-				for (retry = 0; retry < 3; retry++) {
-					int wret;
-					wret = drm_dp_dpcd_write(&intel_dp->aux,
-								 DP_SINK_COUNT_ESI+1,
-								 &esi[1], 3);
-					if (wret == 3) {
-						break;
-					}
-				}
+		DRM_DEBUG_KMS("ESI %3ph\n", esi);
 
-				bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
-				if (bret == true) {
-					DRM_DEBUG_KMS("got esi2 %3ph\n", esi);
-					goto go_again;
-				}
-			} else
-				ret = 0;
+		/* check link status - esi[10] = 0x200c */
+		if (intel_dp->active_mst_links &&
+		    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
+			intel_dp_start_link_train(intel_dp);
+			intel_dp_stop_link_train(intel_dp);
+		}
 
-			return ret;
-		} else {
-			struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
-			DRM_DEBUG_KMS("failed to get ESI - device may have failed\n");
-			intel_dp->is_mst = false;
-			drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
-			/* send a hotplug event */
-			drm_kms_helper_hotplug_event(intel_dig_port->base.base.dev);
+		ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
+		if (!handled)
+			return 0;
+
+		if (ret)
+			DRM_DEBUG_KMS("error handling MST IRQ_HPD %d\n", ret);
+
+		for (retry = 0; retry < 3; retry++) {
+			int wret;
+
+			wret = drm_dp_dpcd_write(&intel_dp->aux,
+						 DP_SINK_COUNT_ESI + 1, &esi[1],
+						 3);
+			if (wret == 3)
+				break;
 		}
 	}
+
+	DRM_DEBUG_KMS("failed to get ESI - device may have failed\n");
+	intel_dp->is_mst = false;
+	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
+	drm_kms_helper_hotplug_event(intel_dig_port->base.base.dev);
 	return -EINVAL;
 }
 
-- 
2.11.0