[PATCH 1/5] dmr/i915: Displayport - Add a function to set the training pattern

Todd Previte
2014-04-08T17:47:57Z

Adds a function to set the training pattern 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 | 2 ++
drivers/gpu/drm/i915/intel_dp.c | 70 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 72 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index adcb9c7..0f0d549 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5303,6 +5303,8 @@ enum punit_power_well {
#define DP_TP_CTL_LINK_TRAIN_NORMAL (3<<8)
#define DP_TP_CTL_SCRAMBLE_DISABLE (1<<7)

+#define DP_TRAINING_PATTERN_MASK_1P2 0x7
+
/* DisplayPort Transport Status */
#define DP_TP_STATUS_A 0x64044
#define DP_TP_STATUS_B 0x64144
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 6f767e5..64c9803 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2356,6 +2356,76 @@ intel_dp_set_signal_levels(struct intel_dp *intel_dp, uint32_t *DP)
*DP = (*DP & ~mask) | signal_levels;
}

+uint32_t
+intel_dp_set_training_pattern(uint8_t training_pattern,
+ struct intel_dp *intel_dp)
+{
+ 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;
+ enum port port = intel_dig_port->port;
+ uint8_t buf[sizeof(intel_dp->train_set) + 1];
+ int ret, len;
+
+ uint32_t reg_value, ctrl_reg, tp_select = 0;
+ uint32_t tp_mask = DP_TRAINING_PATTERN_MASK;
+
+ if (HAS_DDI(dev))
+ ctrl_reg = DP_TP_CTL(port);
+ else
+ ctrl_reg = intel_dp->output_reg;
+
+ reg_value = I915_READ(ctrl_reg);
+
+ // Check DPCD revision to enable TP3
+ if (intel_dp->dpcd[0] >= 12)
+ tp_mask = DP_TRAINING_PATTERN_MASK_1P2;
+
+ // Mask selection above ensures TP3 does not get enabled for < DP 1.2
+ switch (training_pattern & tp_mask) {
+ case DP_TRAINING_PATTERN_DISABLE:
+ tp_select = DP_TP_CTL_LINK_TRAIN_NORMAL;
+ break;
+ case DP_TRAINING_PATTERN_1:
+ tp_select = DP_TP_CTL_LINK_TRAIN_PAT1;
+ break;
+ case DP_TRAINING_PATTERN_2:
+ tp_select = DP_TP_CTL_LINK_TRAIN_PAT2;
+ break;
+ case DP_TRAINING_PATTERN_3:
+ tp_select = DP_TP_CTL_LINK_TRAIN_PAT3;
+ break;
+ }
+
+ if (HAS_DDI(dev) || (HAS_PCH_CPT(dev) && (IS_GEN7(dev) || port != PORT_A))) {
+ reg_value &= ~(tp_mask << 8);
+ reg_value |= tp_select;
+ }
+ else {
+ reg_value &= ~(tp_mask << 28);
+ reg_value |= tp_select << 20;
+ }
+
+ I915_WRITE(ctrl_reg, reg_value);
+ POSTING_READ(ctrl_reg);
+
+ buf[0] = training_pattern;
+ if ((training_pattern & tp_mask) ==
+ DP_TRAINING_PATTERN_DISABLE) {
+ /* don't write DP_TRAINING_LANEx_SET on disable */
+ len = 1;
+ } else {
+ /* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
+ memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
+ len = intel_dp->lane_count + 1;
+ }
+
+ ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
+ buf, len);
+
+ return ret == len;
+}
+
static bool
intel_dp_set_link_train(struct intel_dp *intel_dp,
uint32_t *DP,
--
1.8.3.2