drm/i915: Implement the intel_dp_autotest_edid function for DP EDID complaince tests

Updates the EDID compliance test function to perform the analyze and react to
the EDID data read as a result of a hot plug event. The results of this
analysis are handed off to userspace so that the userspace app can set the
display mode appropriately for the test result/response.

The compliance_test_active flag now appears at the end of the individual
test handling functions. This is so that the kernel-side operations can
be completed without the risk of interruption from the userspace app
that is polling on that flag.

V2:
- Addressed mailing list feedback
- Removed excess debug messages
- Removed extraneous comments
- Fixed formatting issues (line length > 80)
- Updated the debug message in compute_edid_checksum to output hex values
  instead of decimal
V3:
- Addressed more list feedback
- Added the test_active flag to the autotest function
- Removed test_active flag from handler
- Added failsafe check on the compliance test active flag
  at the end of the test handler
- Fixed checkpatch.pl issues
V4:
- Removed the checksum computation function and its use as it has been
  rendered superfluous by changes to the core DRM EDID functions
- Updated to use the raw header corruption detection mechanism
- Moved the declaration of the test_data variable here
V5:
- Update test active flag variable name to match the change in the
  first patch of the series.
- Relocated the test active flag declaration and initialization
  to this patch
V6:
- Updated to use the new flag for raw EDID header corruption
- Removed the extra EDID read from the autotest function
- Added the edid_checksum variable to struct intel_dp so that the
  autotest function can write it to the sink device
- Moved the update to the hpd_pulse function to another patch
- Removed extraneous constants
V7:
- Fixed erroneous placement of the checksum assignment. In some cases
  such as when the EDID read fails and is NULL, this causes a NULL ptr
  dereference in the kernel. Bad news. Fixed now.
V8:
- Updated to support the kfree() on the EDID data added previously
V9:
- Updated for the long_hpd flag propagation
V10:
- Updated to use actual checksum from the EDID read that occurs during
  normal hot plug path execution
- Removed variables from intel_dp struct that are no longer needed
- Updated the patch subject to more closely match the nature and contents
  of the patch
- Fixed formatting problem (long line)
V11:
- Removed extra debug messages
- Updated comments to be more informative
- Removed extra variable
V12:
- Removed the 4 bit offset of the resolution setting in compliance data
- Changed to DRM_DEBUG_KMS instead of DRM_DEBUG_DRIVER

Signed-off-by: Todd Previte <tprevite@gmail.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -41,6 +41,12 @@
 
 #define DP_LINK_CHECK_TIMEOUT	(10 * 1000)
 
+/* Compliance test status bits  */
+#define INTEL_DP_RESOLUTION_SHIFT_MASK	0
+#define INTEL_DP_RESOLUTION_PREFERRED	(1 << INTEL_DP_RESOLUTION_SHIFT_MASK)
+#define INTEL_DP_RESOLUTION_STANDARD	(2 << INTEL_DP_RESOLUTION_SHIFT_MASK)
+#define INTEL_DP_RESOLUTION_FAILSAFE	(3 << INTEL_DP_RESOLUTION_SHIFT_MASK)
+
 struct dp_link_dpll {
 	int link_bw;
 	struct dpll dpll;
@@ -4079,6 +4085,39 @@ static uint8_t intel_dp_autotest_video_pattern(struct intel_dp *intel_dp)
 static uint8_t intel_dp_autotest_edid(struct intel_dp *intel_dp)
 {
 	uint8_t test_result = DP_TEST_NAK;
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	struct drm_connector *connector = &intel_connector->base;
+
+	if (intel_connector->detect_edid == NULL ||
+	    connector->edid_corrupt == 1 ||
+	    intel_dp->aux.i2c_defer_count > 6) {
+		/* Check EDID read for NACKs, DEFERs and corruption
+		 * (DP CTS 1.2 Core r1.1)
+		 *    4.2.2.4 : Failed EDID read, I2C_NAK
+		 *    4.2.2.5 : Failed EDID read, I2C_DEFER
+		 *    4.2.2.6 : EDID corruption detected
+		 * Use failsafe mode for all cases
+		 */
+		if (intel_dp->aux.i2c_nack_count > 0 ||
+			intel_dp->aux.i2c_defer_count > 0)
+			DRM_DEBUG_KMS("EDID read had %d NACKs, %d DEFERs\n",
+				      intel_dp->aux.i2c_nack_count,
+				      intel_dp->aux.i2c_defer_count);
+		intel_dp->compliance_test_data = INTEL_DP_RESOLUTION_FAILSAFE;
+	} else {
+		if (!drm_dp_dpcd_write(&intel_dp->aux,
+					DP_TEST_EDID_CHECKSUM,
+					&intel_connector->detect_edid->checksum,
+					1));
+			DRM_DEBUG_KMS("Failed to write EDID checksum\n");
+
+		test_result = DP_TEST_ACK | DP_TEST_EDID_CHECKSUM_WRITE;
+		intel_dp->compliance_test_data = INTEL_DP_RESOLUTION_STANDARD;
+	}
+
+	/* Set test active flag here so userspace doesn't interrupt things */
+	intel_dp->compliance_test_active = 1;
+
 	return test_result;
 }
 
@@ -4094,7 +4133,10 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 	uint8_t rxdata = 0;
 	int status = 0;
 
+	intel_dp->compliance_test_active = 0;
 	intel_dp->compliance_test_type = 0;
+	intel_dp->compliance_test_data = 0;
+
 	intel_dp->aux.i2c_nack_count = 0;
 	intel_dp->aux.i2c_defer_count = 0;
 

drivers/gpu/drm/i915/intel_drv.h

@@ -740,6 +740,8 @@ struct intel_dp {
 
 	/* Displayport compliance testing */
 	unsigned long compliance_test_type;
+	unsigned long compliance_test_data;
+	bool compliance_test_active;
 };
 
 struct intel_digital_port {