[Intel-gfx] [PATCH] drm/i915: Update intel_dp_hpd_pulse() to check link status for non-MST operation

[Todd Previte]

Update the hot plug function to handle the SST case. Instead of placing
the SST case within the long/short pulse block, it is now handled after
determining that MST mode is not in use. This way, the topology management
layer can handle any MST-related operations while SST operations are still
correctly handled afterwards.

This patch also corrects the problem of SST mode only being handled in the
case of a short (0.5ms - 1.0ms) HPD pulse. For compliance testing purposes
both short and long pulses are used by the different tests, thus both cases
need to be addressed for SST.

This patch replaces [PATCH 10/10] drm/i915: Fix intel_dp_hot_plug() in the
previous compliance testing patch sequence. Review feedback on that patch
indicated that updating intel_dp_hot_plug() was not the correct place for
the test handler.

For the SST case, the main stream is disabled for long HPD pulses as this
generally indicates either a connect/disconnect event or link failure. For
a number of case in compliance testing, the source is required to disable
the main link upon detection of a long HPD.

V2:
- N/A
V3:
- Place the SST mode link status check into the mst_fail case
- Remove obsolete comment regarding SST mode operation
- Removed an erroneous line of code that snuck in during rebasing
V4:
- Added a disable of the main stream (DP transport) for the long pulse case
  for SST to support compliance testing

Signed-off-by: Todd PRevite <tprevite at gmail.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 080cc23..2460d14 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4618,16 +4618,6 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
 			if (intel_dp_check_mst_status(intel_dp) == -EINVAL)
 				goto mst_fail;
 		}
-
-		if (!intel_dp->is_mst) {
-			/*
-			 * we'll check the link status via the normal hot plug path later -
-			 * but for short hpds we should check it now
-			 */
-			drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
-			intel_dp_check_link_status(intel_dp);
-			drm_modeset_unlock(&dev->mode_config.connection_mutex);
-		}
 	}
 
 	ret = IRQ_HANDLED;
@@ -4639,6 +4629,21 @@ mst_fail:
 		DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n", intel_dp->is_mst, intel_dp->mst_mgr.mst_state);
 		intel_dp->is_mst = false;
 		drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
+	} else {
+		/* SST mode - handle short/long pulses here */
+		drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+		/* Clear compliance testing flags/data here to prevent
+		 * false detection in userspace */
+		intel_dp->compliance_test_data = 0;
+		intel_dp->compliance_testing_active = 0;
+		/* For a long pulse in SST mode, disable the main link */
+		if (long_hpd) {
+			I915_WRITE(DP_TP_CTL(intel_dig_port->port),
+					      ~DP_TP_CTL_ENABLE);
+		}
+		intel_dp_check_link_status(intel_dp);
+		drm_modeset_unlock(&dev->mode_config.connection_mutex);
+		ret = IRQ_HANDLED;
 	}
 put_power:
 	intel_display_power_put(dev_priv, power_domain);
-- 
1.9.1