drm/i915: debugfs: Add support for probing DP sink CRC.

This debugfs interface will allow intel-gpu-tools test case
to verify if screen has been updated properly on cases like PSR.

v2: Accepted all Daniel's suggestions:
    * grab modeset lock
    * loop over connector and check DPMS on
    * return errors
    * use _eDP1 suffix for easy future extension
    * don't cache crc_supported neither latest crc
    * return crc as a full array and read it at once with aux.
    * use 0 to turn TEST_SINK off.
    * split the drm_helpers definitions in another patch.

v3: Accepted 2 Damien's suggestion: remove h from printf hexa
    and return ENODEV when eDP not present instead of EAGAIN.

v4: Accepted 2 Jani' s suggestion: 1 path for unlock and remove
    _retry from aux read.

v5: removing last missing useless _retry (by Damien)

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1920,6 +1920,44 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
 	return 0;
 }
 
+static int i915_sink_crc(struct seq_file *m, void *data)
+{
+	struct drm_info_node *node = m->private;
+	struct drm_device *dev = node->minor->dev;
+	struct intel_encoder *encoder;
+	struct intel_connector *connector;
+	struct intel_dp *intel_dp = NULL;
+	int ret;
+	u8 crc[6];
+
+	drm_modeset_lock_all(dev);
+	list_for_each_entry(connector, &dev->mode_config.connector_list,
+			    base.head) {
+
+		if (connector->base.dpms != DRM_MODE_DPMS_ON)
+			continue;
+
+		encoder = to_intel_encoder(connector->base.encoder);
+		if (encoder->type != INTEL_OUTPUT_EDP)
+			continue;
+
+		intel_dp = enc_to_intel_dp(&encoder->base);
+
+		ret = intel_dp_sink_crc(intel_dp, crc);
+		if (ret)
+			goto out;
+
+		seq_printf(m, "%02x%02x%02x%02x%02x%02x\n",
+			   crc[0], crc[1], crc[2],
+			   crc[3], crc[4], crc[5]);
+		goto out;
+	}
+	ret = -ENODEV;
+out:
+	drm_modeset_unlock_all(dev);
+	return ret;
+}
+
 static int i915_energy_uJ(struct seq_file *m, void *data)
 {
 	struct drm_info_node *node = m->private;
@@ -3276,6 +3314,7 @@ static const struct drm_info_list i915_debugfs_list[] = {
 	{"i915_dpio", i915_dpio_info, 0},
 	{"i915_llc", i915_llc, 0},
 	{"i915_edp_psr_status", i915_edp_psr_status, 0},
+	{"i915_sink_crc_eDP1", i915_sink_crc, 0},
 	{"i915_energy_uJ", i915_energy_uJ, 0},
 	{"i915_pc8_status", i915_pc8_status, 0},
 	{"i915_power_domain_info", i915_power_domain_info, 0},

drivers/gpu/drm/i915/intel_dp.c

@@ -2922,6 +2922,35 @@ intel_dp_probe_oui(struct intel_dp *intel_dp)
 	edp_panel_vdd_off(intel_dp, false);
 }
 
+int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
+{
+	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	struct drm_device *dev = intel_dig_port->base.base.dev;
+	struct intel_crtc *intel_crtc =
+		to_intel_crtc(intel_dig_port->base.base.crtc);
+	u8 buf[1];
+
+	if (!intel_dp_aux_native_read(intel_dp, DP_TEST_SINK_MISC, buf, 1))
+		return -EAGAIN;
+
+	if (!(buf[0] & DP_TEST_CRC_SUPPORTED))
+		return -ENOTTY;
+
+	if (!intel_dp_aux_native_write_1(intel_dp, DP_TEST_SINK,
+					 DP_TEST_SINK_START))
+		return -EAGAIN;
+
+	/* Wait 2 vblanks to be sure we will have the correct CRC value */
+	intel_wait_for_vblank(dev, intel_crtc->pipe);
+	intel_wait_for_vblank(dev, intel_crtc->pipe);
+
+	if (!intel_dp_aux_native_read(intel_dp, DP_TEST_CRC_R_CR, crc, 6))
+		return -EAGAIN;
+
+	intel_dp_aux_native_write_1(intel_dp, DP_TEST_SINK, 0);
+	return 0;
+}
+
 static bool
 intel_dp_get_sink_irq(struct intel_dp *intel_dp, u8 *sink_irq_vector)
 {

drivers/gpu/drm/i915/intel_drv.h

@@ -738,6 +738,7 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
 void intel_dp_encoder_destroy(struct drm_encoder *encoder);
 void intel_dp_check_link_status(struct intel_dp *intel_dp);
+int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc);
 bool intel_dp_compute_config(struct intel_encoder *encoder,
 			     struct intel_crtc_config *pipe_config);
 bool intel_dp_is_edp(struct drm_device *dev, enum port port);