[PATCH 5/5] drm/i915: Displayport - Add function to execute a single iteration of channel equalization

Todd Previte
2014-04-08T17:48:18Z

Adds a function to execute a single iteration of the channel equalization
sequence for Displayport. This is functionality required to establish more
fine-grained control over the Displayport interface, both for operational
reliability and compliance testing.

Signed-off-by: Todd Previte <tprevite@gmail.com>
---
drivers/gpu/drm/i915/intel_dp.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 6baa26c..66dbda6 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2878,6 +2878,37 @@ exit:
return clock_recovery_status;
}

+uint32_t intel_dp_exec_channel_equalization(struct intel_dp *intel_dp)
+{
+ uint32_t channel_equalization_status = DP_CHANNEL_EQUALIZATION_FAILED;
+ uint8_t link_status[DP_LINK_STATUS_SIZE];
+
+ // Set the correct training pattern
+ if (intel_dp->dpcd[DP_DPCD_REV] >= 0x12)
+ intel_dp_set_training_pattern(DP_TRAINING_PATTERN_2, intel_dp);
+ else
+ intel_dp_set_training_pattern(DP_TRAINING_PATTERN_2, intel_dp);
+
+ // Wait for channel equalization time period to expire
+ drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
+
+ // Check link status
+ if (!intel_dp_get_link_status(intel_dp, link_status)) {
+ channel_equalization_status = DP_LINK_STATUS_READ_FAILED;
+ goto exit;
+ }
+
+ // Verify that both CR is still valid and CE is successful
+ if (intel_dp_verify_link_status(DP_LINK_TRAINING_STATE_CLOCK_REC,
+ intel_dp->lane_count, link_status) &&
+ intel_dp_verify_link_status(DP_LINK_TRAINING_STATE_CHANNEL_EQ,
+ intel_dp->lane_count, link_status))
+ channel_equalization_status = DP_CHANNEL_EQUALIZATION_COMPLETE;
+
+exit:
+ return channel_equalization_status;
+}
+
static void
intel_dp_link_down(struct intel_dp *intel_dp)
{
--
1.8.3.2