[PATCH 07/10] drm/i915: Support EDID compliance tests with the intel_dp_autotest_edid() function

[Todd Previte <tprevite@gmail.com>]

Updates the EDID compliance test function to perform the EDID read as
required by the tests. This read needs to take place in the kernel for
reasons of speed and efficiency. The results of the EDID read operations
are handed off to userspace so that the userspace app can set the display
mode appropriately for the test 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

Signed-off-by: Todd Previte <tprevite@gmail.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 47 +++++++++++++++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_drv.h |  4 ++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index f70d20e..033b0ef 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/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	4
+#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;
@@ -3994,6 +4000,35 @@ 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;
+	uint32_t ret = 0;
+
+	if (intel_dp->compliance_edid_invalid ||
+	    intel_dp->aux.i2c_defer_count > 6) {
+		/* Check for NACKs/DEFERs, use failsafe if detected
+		 *  (DP CTS 1.2 Core Rev 1.1, 4.2.2.4, 4.2.2.5)
+		 */
+		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 {
+		ret = drm_dp_dpcd_write(&intel_dp->aux,
+					DP_TEST_EDID_CHECKSUM,
+					&intel_dp->compliance_edid_checksum, 1);
+		if (ret <= 0)
+			DRM_DEBUG_DRIVER("Failed to write EDID checksum\n");
+		else
+			DRM_DEBUG_DRIVER("EDID checksum written to sink\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;
 }
 
@@ -4010,7 +4045,10 @@ 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;
 
@@ -4137,11 +4175,18 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
 
 	/* Displayport Link CTS Core 1.2 rev1.1 EDID testing
 	 * 4.2.2.1 - EDID read required for all HPD events
-	 */
+	 * Also used for 4.2.2.3, 4.2.2.4 4.2.2.5 and 4.2.2.6
+	 *   - compliance_edid_invalid flag used for 4.2.2.6
+	 *   - compliance_edid_checksum used for 4.2.2.3
+	*/
+	intel_dp->compliance_edid_invalid = 0;
 	edid_read = drm_get_edid(connector, adapter);
 	if (!edid_read || connector->edid_header_corrupt == 1) {
 		DRM_DEBUG_DRIVER("Invalid EDID detected\n");
+		intel_dp->compliance_edid_invalid = 1;
+		intel_dp->compliance_edid_checksum = 0;
 	} else {
+		intel_dp->compliance_edid_checksum = edid_read->checksum;
 		kfree(edid_read);
 	}
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index accf08b..73ced46 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -742,6 +742,10 @@ struct intel_dp {
 
 	/* Displayport compliance testing */
 	unsigned long compliance_test_type;
+	unsigned long compliance_test_data;
+	bool compliance_test_active;
+	bool compliance_edid_invalid;
+	uint8_t compliance_edid_checksum;
 };
 
 struct intel_digital_port {
-- 
1.9.1

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