[PATCH 4/5] drm/i915: Displayport - Add function for executing a single iteration of clock recovery

Todd Previte
2014-04-08T17:48:14Z

Adds a function to execute a single iteration of the clock recovery
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/i915_reg.h | 6 ++++++
drivers/gpu/drm/i915/intel_dp.c | 30 +++++++++++++++++++++++++++++-
2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 0f0d549..eebc4f2 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5304,6 +5304,12 @@ enum punit_power_well {
#define DP_TP_CTL_SCRAMBLE_DISABLE (1<<7)

#define DP_TRAINING_PATTERN_MASK_1P2 0x7
+#define DP_CLOCK_RECOVERY_COMPLETE 0x0
+#define DP_CLOCK_RECOVERY_FAILED 0x1
+#define DP_LINK_STATUS_READ_FAILED 0x2
+#define DP_CHANNEL_EQUALIZATION_COMPLETE 0x0
+#define DP_CHANNEL_EQUALIZATION_FAILED 0x1
+#define DP_SYMBOL_LOCK_FAILED 0x1

/* DisplayPort Transport Status */
#define DP_TP_STATUS_A 0x64044
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 1209de8..6baa26c 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2466,7 +2466,7 @@ intel_dp_set_training_pattern(uint8_t training_pattern,
reg_value = I915_READ(ctrl_reg);

// Check DPCD revision to enable TP3
- if (intel_dp->dpcd[0] >= 12)
+ if (intel_dp->dpcd[DP_DPCD_REV] >= 0x12)
tp_mask = DP_TRAINING_PATTERN_MASK_1P2;

// Mask selection above ensures TP3 does not get enabled for < DP 1.2
@@ -2850,6 +2850,34 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
DP_TRAINING_PATTERN_DISABLE);
}

+// State-based link training functions
+// FIXME: Remove these comments before commit!
+uint32_t intel_dp_exec_clock_recovery(struct intel_dp *intel_dp)
+{
+ uint32_t clock_recovery_status = DP_CLOCK_RECOVERY_FAILED;
+ uint8_t link_status[DP_LINK_STATUS_SIZE];
+
+ // Set the training pattern for clock recovery
+ intel_dp_set_training_pattern(DP_TRAINING_PATTERN_1, intel_dp);
+
+ // Wait for clock recovery time period to expire
+ drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
+
+ // Check link status
+ if (!intel_dp_get_link_status(intel_dp, link_status)) {
+ clock_recovery_status = DP_LINK_STATUS_READ_FAILED;
+ goto exit;
+ }
+
+ // Verify clock recovery is successful
+ if (intel_dp_verify_link_status(DP_LINK_TRAINING_STATE_CLOCK_REC,
+ intel_dp->lane_count, link_status))
+ clock_recovery_status = DP_CLOCK_RECOVERY_COMPLETE;
+
+exit:
+ return clock_recovery_status;
+}
+
static void
intel_dp_link_down(struct intel_dp *intel_dp)
{
--
1.8.3.2