Reuse existing DP link training values i.e. voltage swing
and pre-emphasis levels, if DP port that we are connected
to hasn't changed. If we are unable to re-initialize DP
link, the fallback is to reset the link training values,
and restart.
modified: intel_dp.c
modified: intel_drv.h
---
drivers/gpu/drm/i915/intel_dp.c | 75 +++++++++++++++++++++++++++++++++++-----
drivers/gpu/drm/i915/intel_drv.h | 2 ++
2 files changed, 69 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 868a07b..c40d64a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3286,6 +3286,25 @@ intel_dp_reset_link_train(struct intel_dp *intel_dp, uint32_t *DP,
}
static bool
+intel_dp_reuse_link_train(struct intel_dp *intel_dp, uint32_t *DP,
+ uint8_t dp_train_pat)
+{
+ struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+ struct drm_device *dev = intel_dig_port->base.base.dev;
+ struct drm_i915_private *dev_priv = dev->dev_private;
+
+ intel_dp_set_signal_levels(intel_dp, DP);
+
+ I915_WRITE(intel_dp->output_reg, *DP);
+ POSTING_READ(intel_dp->output_reg);
+
+ drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
+ intel_dp->train_set, intel_dp->lane_count);
+
+ return intel_dp_set_link_train(intel_dp, DP, dp_train_pat);
+}
+
+static bool
intel_dp_update_link_train(struct intel_dp *intel_dp, uint32_t *DP,
const uint8_t link_status[DP_LINK_STATUS_SIZE])
{
@@ -3348,6 +3367,8 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
int voltage_tries, loop_tries;
uint32_t DP = intel_dp->DP;
uint8_t link_config[2];
+ uint8_t link_status[DP_LINK_STATUS_SIZE];
+ bool reuse_train_set = false;
if (HAS_DDI(dev))
intel_ddi_prepare_link_retrain(encoder);
@@ -3365,20 +3386,36 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
DP |= DP_PORT_EN;
- /* clock recovery */
- if (!intel_dp_reset_link_train(intel_dp, &DP,
- DP_TRAINING_PATTERN_1 |
- DP_LINK_SCRAMBLING_DISABLE)) {
- DRM_ERROR("failed to enable link training\n");
- return;
+ /*
+ * check if DP connector has changed. Reset voltage swing and
+ * pre-emphasis levels if that's the case.
+ */
+ if (intel_dp->connector_changed) {
+ /* reset link training values */
+ DRM_DEBUG_KMS("resetting link train set\n");
+ if (!intel_dp_reset_link_train(intel_dp, &DP,
+ DP_TRAINING_PATTERN_1 |
+ DP_LINK_SCRAMBLING_DISABLE)) {
+ DRM_ERROR("failed to enable link training\n");
+ return;
+ }
+ reuse_train_set = false;
+ }
+ else {
+ DRM_DEBUG_KMS("reusing current link train set\n");
+ if (!intel_dp_reuse_link_train(intel_dp, &DP,
+ DP_TRAINING_PATTERN_1 |
+ DP_LINK_SCRAMBLING_DISABLE)) {
+ DRM_DEBUG_KMS("unable to set known link training values\n");
+ return;
+ }
+ reuse_train_set = true;
}
voltage = 0xff;
voltage_tries = 0;
loop_tries = 0;
for (;;) {
- uint8_t link_status[DP_LINK_STATUS_SIZE];
-
drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
if (!intel_dp_get_link_status(intel_dp, link_status)) {
DRM_ERROR("failed to get link status\n");
@@ -3389,6 +3426,20 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
DRM_DEBUG_KMS("clock recovery OK\n");
break;
}
+ /*
+ * if we used previously trained voltage and pre-emphasis values
+ * and we don't get clock recovery, reset link training values
+ */
+ if (reuse_train_set) {
+ DRM_DEBUG_KMS("clock recovery not ok, resetting DP train set\n");
+ if (!intel_dp_reset_link_train(intel_dp, &DP,
+ DP_TRAINING_PATTERN_1 |
+ DP_LINK_SCRAMBLING_DISABLE)) {
+ DRM_ERROR("failed to enable link training\n");
+ return;
+ }
+ reuse_train_set = false;
+ }
/* Check to see if we've tried the max voltage */
for (i = 0; i < intel_dp->lane_count; i++)
@@ -4076,6 +4127,14 @@ intel_dp_detect(struct drm_connector *connector, bool force)
connector->base.id, connector->name);
intel_dp_unset_edid(intel_dp);
+ if (connector->base.id != intel_dp->connector_id) {
+ intel_dp->connector_id = connector->base.id;
+ DRM_DEBUG_KMS("DP connector changed\n");
+ intel_dp->connector_changed = true;
+ }
+ else
+ intel_dp->connector_changed = false;
+
if (intel_dp->is_mst) {
/* MST devices are disconnected from a monitor POV */
if (intel_encoder->type != INTEL_OUTPUT_EDP)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 1de8e20..2877226 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -648,6 +648,8 @@ struct intel_dp {
bool has_aux_irq,
int send_bytes,
uint32_t aux_clock_divider);
+ uint32_t connector_id;
+ bool connector_changed;
};
struct intel_digital_port {
--
1.9.1
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