[Intel-gfx] [PATCH 2/2] drm/i915: Add support for Displayport compliance test 4.2.2.8

[Todd Previte]

Adds support for the test 4.2.2.8 EDID read on IRQ_HPD event after
Branch Device Detection in the Displayport Link CTS Core 1.2 rev1.1.
This test checks to see that the source device reads the EDID from
the attached sink device upon detection of a downstream port. A short
pulse is generated by the sink device to indicate a status change in
the downstream ports to which the source device must respond by
reading the EDID from the attached sink.

Signed-off-by: Todd Previte <tprevite at gmail.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 7e0d3a8..c27c30a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4015,6 +4015,14 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
 		return;
 	}
 
+	/* Check for downstream port status changes
+	   Displayport Link CTS 1.2a rev1.1 4.2.2.8
+	*/
+	if (link_status[2] & DP_DOWNSTREAM_PORT_STATUS_CHANGED) {
+		/* Read EDID as required by 4.2.2.8 */
+		edid_read = drm_get_edid(connector, adapter);
+	}
+
 	if (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count)) {
 		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
 			      intel_encoder->base.name);
-- 
1.9.1