[Intel-gfx] [PATCH 5/9] drm/i915: Update the EDID automated compliance test function

[Todd Previte]

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

Signed-off-by: Todd Previte <tprevite at gmail.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 89 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 88 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5d7b7f3..e69cdad 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -41,6 +41,13 @@
 
 #define DP_LINK_CHECK_TIMEOUT	(10 * 1000)
 
+/* Compliance test status bits  */
+#define  INTEL_DP_EDID_OK		(0<<0)
+#define  INTEL_DP_EDID_CORRUPT		(1<<0)
+#define  INTEL_DP_RESOLUTION_PREFERRED	(1<<2)
+#define  INTEL_DP_RESOLUTION_STANDARD	(1<<3)
+#define  INTEL_DP_RESOLUTION_FAILSAFE	(1<<4)
+
 struct dp_link_dpll {
 	int link_bw;
 	struct dpll dpll;
@@ -3764,9 +3771,76 @@ static uint8_t intel_dp_autotest_video_pattern(struct intel_dp *intel_dp)
 	return test_result;
 }
 
+static bool intel_dp_compute_edid_checksum(uint8_t *edid_data,
+					   uint8_t *edid_checksum)
+{
+	uint32_t byte_total = 0;
+	uint8_t i = 0;
+	bool edid_ok = true;
+
+	/* Don't include last byte (the checksum) in the computation */
+	for (i = 0; i < EDID_LENGTH - 2; i++)
+		byte_total += edid_data[i];
+
+	*edid_checksum = 256 - (byte_total % 256);
+
+	if (*edid_checksum != edid_data[EDID_LENGTH - 1]) {
+		DRM_DEBUG_KMS("Invalid EDID checksum %02x, should be %02x\n",
+			      edid_data[EDID_LENGTH - 40 - 1], *edid_checksum);
+		edid_ok = false;
+	}
+
+	return edid_ok;
+}
+
 static uint8_t intel_dp_autotest_edid(struct intel_dp *intel_dp)
 {
-	uint8_t test_result = DP_TEST_NAK;
+	struct drm_connector *connector = &intel_dp->attached_connector->base;
+	struct i2c_adapter *adapter = &intel_dp->aux.ddc;
+	struct edid *edid_read = NULL;
+	uint8_t *edid_data = NULL;
+	uint8_t test_result = DP_TEST_NAK, checksum = 0;
+	uint32_t ret = 0;
+
+	intel_dp->aux.i2c_nack_count = 0;
+	intel_dp->aux.i2c_defer_count = 0;
+
+
+	edid_read = drm_get_edid(connector, adapter);
+
+	if (edid_read == NULL) {
+		/* 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_EDID_CORRUPT |
+						 INTEL_DP_RESOLUTION_FAILSAFE;
+	} else {
+		edid_data = (uint8_t *) edid_read;
+
+		if (intel_dp_compute_edid_checksum(edid_data, &checksum)) {
+			ret = drm_dp_dpcd_write(&intel_dp->aux,
+						DP_TEST_EDID_CHECKSUM,
+						&edid_read->checksum, 1);
+			test_result = DP_TEST_ACK |
+				      DP_TEST_EDID_CHECKSUM_WRITE;
+			intel_dp->compliance_test_data =
+				INTEL_DP_EDID_OK |
+				INTEL_DP_RESOLUTION_PREFERRED;
+		} else {
+			/* Invalid checksum - EDID corruption detection */
+			intel_dp->compliance_test_data =
+				INTEL_DP_EDID_CORRUPT |
+				INTEL_DP_RESOLUTION_FAILSAFE;
+		}
+	}
+
+	/* Set test active flag here so userspace doesn't interrupt things */
+	intel_dp->compliance_testing_active = 1;
+
 	return test_result;
 }
 
@@ -3781,6 +3855,7 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 	uint8_t response = DP_TEST_NAK;
 	uint8_t rxdata = 0;
 	int status = 0;
+	int failsafe_counter = 0;
 
 	status = drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_REQUEST, &rxdata, 1);
 	if (status <= 0) {
@@ -3816,6 +3891,18 @@ update_status:
 				   &response, 1);
 	if (status <= 0)
 		DRM_DEBUG_KMS("Could not write test response to sink\n");
+
+	/* Failsafe check on compliance testing flag */
+	while (intel_dp->compliance_testing_active) {
+		usleep_range(100, 150);
+		failsafe_counter++;
+		/*
+		   If userspace still hasn't responded after 20 iterations,
+		   chances are it's not going to, so clear the flag and move on
+		*/
+		if (failsafe_counter > 20)
+			intel_dp->compliance_testing_active = 0;
+	}
 }
 
 static int
-- 
1.9.1