[Intel-gfx] [PATCH 2/5] drm/i915: Read test values for lane_count and link_rate

[Shubhangi Shrivastava]

During automated test request for link training we are supposed to
read the TEST_LANE_COUNT and TEST_LINK_RATE dpcd registers and use
respective values in the next link training. This patch adds
reading and updating of these values.

Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani at intel.com>
Signed-off-by: Shubhangi Shrivastava <shubhangi.shrivastava at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 2a14603..0402a4b 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4045,9 +4045,34 @@ intel_dp_get_sink_irq_esi(struct intel_dp *intel_dp, u8 *sink_irq_vector)
 	return true;
 }
 
+/*
+ * This function reads TEST_LANE_COUNT & TEST_LINK_RATE and updates
+ * them to cached dpcd values, thus the new values are implicitly
+ * used by rest of the code without need to be aware of the change.
+ */
 static uint8_t intel_dp_autotest_link_training(struct intel_dp *intel_dp)
 {
 	uint8_t test_result = DP_TEST_ACK;
+	uint8_t dpcd_val, ret;
+
+	ret = intel_dp_dpcd_read_wake(&intel_dp->aux,
+				      DP_TEST_LANE_COUNT,
+				      &dpcd_val, 1);
+
+	/* update values only if read returned 1 byte */
+	if (ret == 1) {
+		dpcd_val &= DP_MAX_LANE_COUNT_MASK;
+		intel_dp->dpcd[DP_MAX_LANE_COUNT] &= ~(DP_MAX_LANE_COUNT_MASK);
+		intel_dp->dpcd[DP_MAX_LANE_COUNT] |= dpcd_val;
+	}
+
+	ret = intel_dp_dpcd_read_wake(&intel_dp->aux,
+				      DP_TEST_LINK_RATE,
+				      &dpcd_val, 1);
+
+	if (ret == 1)
+		intel_dp->dpcd[DP_MAX_LINK_RATE] = dpcd_val;
+
 	return test_result;
 }
 
-- 
2.6.1