[PATCH 1/4] drm/i915: Add support for DP link training compliance

[Manasi Navare]

This patch adds support to handle automated DP compliance
link training test requests. This patch has been tested with
Unigraf DPR-120 DP Compliance device for testing Link
Training Compliance.
After we get a short pulse Compliance test request, test
request values are read and hotplug uevent is sent in order
to trigger another modeset during which the pipe is configured
and link is retrained and enabled for link parameters requested
by the test.

v3:
* Validate the test link rate and lane count as soon as
the erquest comes (Jani Nikula)
v2:
* Validate the test lane count before using it in
intel_dp_compute_config (Jani Nikula)
Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 60 ++++++++++++++++++++++++++++++++++++----
 drivers/gpu/drm/i915/intel_drv.h |  2 ++
 2 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index e80d620..3e76b63 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1613,6 +1613,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 	/* Conveniently, the link BW constants become indices with a shift...*/
 	int min_clock = 0;
 	int max_clock;
+	int link_rate_index;
 	int bpp, mode_rate;
 	int link_avail, link_clock;
 	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
@@ -1654,6 +1655,15 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
 		return false;
 
+	/* Use values requested by Compliance Test Request */
+	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
+		link_rate_index = intel_dp_link_rate_index(intel_dp,
+							   common_rates,
+							   drm_dp_bw_code_to_link_rate(intel_dp->compliance.test_link_rate));
+		if (link_rate_index >= 0)
+			min_clock = max_clock = link_rate_index;
+		min_lane_count = max_lane_count = intel_dp->compliance.test_lane_count;
+	}
 	DRM_DEBUG_KMS("DP link computation with max lane count %i "
 		      "max bw %d pixel clock %iKHz\n",
 		      max_lane_count, common_rates[max_clock],
@@ -3920,7 +3930,42 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
 
 static uint8_t intel_dp_autotest_link_training(struct intel_dp *intel_dp)
 {
-	uint8_t test_result = DP_TEST_ACK;
+	uint8_t test_result = DP_TEST_NAK;
+	int status = 0;
+	int min_lane_count = 1;
+	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
+	int link_rate_index;
+	/* (DP CTS 1.2)
+	 * 4.3.1.11
+	 */
+	/* Read the TEST_LANE_COUNT and TEST_LINK_RTAE fields (DP CTS 3.1.4) */
+	status = drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_LANE_COUNT,
+				  &intel_dp->compliance.test_lane_count);
+
+	if (status <= 0) {
+		DRM_DEBUG_KMS("Lane count read failed\n");
+		return 0;
+	}
+	intel_dp->compliance.test_lane_count &= DP_MAX_LANE_COUNT_MASK;
+	/* Validate the requested lane count */
+	if (intel_dp->compliance.test_lane_count < min_lane_count ||
+	    intel_dp->compliance.test_lane_count > intel_dp->max_sink_lane_count)
+		return test_result;
+
+	status = drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_LINK_RATE,
+				   &intel_dp->compliance.test_link_rate);
+	if (status <= 0) {
+		DRM_DEBUG_KMS("Link Rate read failed\n");
+		return 0;
+	}
+	/* Validate the requested link rate */
+	link_rate_index = intel_dp_link_rate_index(intel_dp,
+						   common_rates,
+						   drm_dp_bw_code_to_link_rate(intel_dp->compliance.test_link_rate));
+	if (link_rate_index < 0)
+		return test_result;
+
+	test_result = DP_TEST_ACK;
 	return test_result;
 }
 
@@ -4135,9 +4180,8 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 	if (!intel_dp->lane_count)
 		return;
 
-	/* if link training is requested we should perform it always */
-	if ((intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) ||
-	    (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {
+	/* Retrain if Channel EQ or CR not ok */
+	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);
 
@@ -4162,6 +4206,7 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 intel_dp_short_pulse(struct intel_dp *intel_dp)
 {
 	struct drm_device *dev = intel_dp_to_dev(intel_dp);
+	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
 	u8 sink_irq_vector = 0;
 	u8 old_sink_count = intel_dp->sink_count;
 	bool ret;
@@ -4195,7 +4240,7 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 				   sink_irq_vector);
 
 		if (sink_irq_vector & DP_AUTOMATED_TEST_REQUEST)
-			DRM_DEBUG_DRIVER("Test request in short pulse not handled\n");
+			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");
 	}
@@ -4203,6 +4248,11 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 	intel_dp_check_link_status(intel_dp);
 	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
+		DRM_DEBUG_KMS("Link Training Compliance Test requested\n");
+		/* Send a Hotplug Uevent to userspace to start modeset */
+		drm_kms_helper_hotplug_event(intel_encoder->base.dev);
+	}
 
 	return true;
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 0cec001..1586a02 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -894,6 +894,8 @@ struct intel_dp_compliance {
 	unsigned long test_type;
 	struct intel_dp_compliance_data test_data;
 	bool test_active;
+	u8 test_link_rate;
+	u8 test_lane_count;
 };
 
 struct intel_dp {
-- 
1.9.1