[Intel-gfx] [PATCH 03/11] drm/i915: Move the DPCD read further up in intel_dp_check_link_status()

[Todd Previte]

Move the DPCD read to the top and check for an interrupt from the sink to catch
Displayport automated testing requests necessary to support Displayport
compliance testing. The checks for active connectors and link status are moved
below the check for the interrupt.

The main reason for doing this is to make sure that a test request isn't missed.
Checking for the status of the encoder/crtc isn't necessary for some test cases
(AUX channel tests are one example) and without moving the check for the
interrupt, these tests may not execute if one of those checks fails.
Additionally, if reading the DPCD fails, regardless of whether or not testing is
happening, there's no way to train the link since configurations and status
can't be read, nor can link training parameters be written.

V1:
- This is the second part of the single-patch split previously
  mentioned.

Signed-off-by: Todd Previte <tprevite at gmail.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 30cd433..23184b0 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3913,13 +3913,26 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
 		drm_dp_dpcd_writeb(&intel_dp->aux,
 				   DP_DEVICE_SERVICE_IRQ_VECTOR,
 				   sink_irq_vector);
-
 		if (sink_irq_vector & DP_AUTOMATED_TEST_REQUEST)
 			intel_dp_handle_test_request(intel_dp);
 		if (sink_irq_vector & (DP_CP_IRQ | DP_SINK_SPECIFIC_IRQ))
 			DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
 	}
 
+	if (!intel_encoder->connectors_active)
+		return;
+
+	if (WARN_ON(!intel_encoder->base.crtc))
+		return;
+
+	if (!to_intel_crtc(intel_encoder->base.crtc)->active)
+		return;
+
+	/* Try to read receiver status if the link appears to be up */
+	if (!intel_dp_get_link_status(intel_dp, link_status)) {
+		return;
+	}
+
 	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