[Intel-gfx] [PATCH 2/2] drm/i915/dg2: update link training for 128b/132b

Jani Nikula
2021-10-11T18:22:02Z

The 128b/132b channel coding link training uses more straightforward TX
FFE preset values. Reuse voltage tries and max vswing for retry logic.

The delays for 128b/132b are still all wrong, but this is regardless a
step forward.

v2: Fix UHBR rate checks, use intel_dp_is_uhbr() helper

v3:
- Rebase
- Modify intel_dp_adjust_request_changed() and
intel_dp_link_max_vswing_reached() to take 128b/132b into
account. (Ville)

v4:
- Train request printing for TX FFE (Ville)
- Log 8b/10b vs. 128b/132b (Ville)
- Add helper for per-lane max vswing / tx ffe (Ville)
- Name functions with tx_ffe/vswing instead of 128b132b/8b10b

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
drivers/gpu/drm/i915/display/intel_ddi.c | 18 ++-
.../drm/i915/display/intel_dp_link_training.c | 152 ++++++++++++++----
2 files changed, 134 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index 3f7bbeb3e3cd..59428ce4f8c1 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -1338,13 +1338,20 @@ static int translate_signal_level(struct intel_dp *intel_dp,
return 0;
}

-static int intel_ddi_dp_level(struct intel_dp *intel_dp, int lane)
+static int intel_ddi_dp_level(struct intel_dp *intel_dp,
+ const struct intel_crtc_state *crtc_state,
+ int lane)
{
u8 train_set = intel_dp->train_set[lane];
- u8 signal_levels = train_set & (DP_TRAIN_VOLTAGE_SWING_MASK |
- DP_TRAIN_PRE_EMPHASIS_MASK);

- return translate_signal_level(intel_dp, signal_levels);
+ if (intel_dp_is_uhbr(crtc_state)) {
+ return train_set & DP_TX_FFE_PRESET_VALUE_MASK;
+ } else {
+ u8 signal_levels = train_set & (DP_TRAIN_VOLTAGE_SWING_MASK |
+ DP_TRAIN_PRE_EMPHASIS_MASK);
+
+ return translate_signal_level(intel_dp, signal_levels);
+ }
}

int intel_ddi_level(struct intel_encoder *encoder,
@@ -1362,7 +1369,8 @@ int intel_ddi_level(struct intel_encoder *encoder,
if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI))
level = intel_ddi_hdmi_level(encoder, trans);
else
- level = intel_ddi_dp_level(enc_to_intel_dp(encoder), lane);
+ level = intel_ddi_dp_level(enc_to_intel_dp(encoder), crtc_state,
+ lane);

if (drm_WARN_ON_ONCE(&i915->drm, level >= n_entries))
level = n_entries - 1;
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 1d4bcb91cd3b..fda9f15ea7e9 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -304,11 +304,33 @@ static bool has_per_lane_signal_levels(struct intel_dp *intel_dp,
return !intel_dp_phy_is_downstream_of_source(intel_dp, dp_phy);
}

-static u8 intel_dp_get_lane_adjust_train(struct intel_dp *intel_dp,
- const struct intel_crtc_state *crtc_state,
- enum drm_dp_phy dp_phy,
- const u8 link_status[DP_LINK_STATUS_SIZE],
- int lane)
+
+/* 128b/132b */
+static u8 intel_dp_get_lane_adjust_tx_ffe_preset(struct intel_dp *intel_dp,
+ const struct intel_crtc_state *crtc_state,
+ enum drm_dp_phy dp_phy,
+ const u8 link_status[DP_LINK_STATUS_SIZE],
+ int lane)
+{
+ u8 tx_ffe = 0;
+
+ if (has_per_lane_signal_levels(intel_dp, dp_phy)) {
+ lane = min(lane, crtc_state->lane_count - 1);
+ tx_ffe = drm_dp_get_adjust_tx_ffe_preset(link_status, lane);
+ } else {
+ for (lane = 0; lane < crtc_state->lane_count; lane++)
+ tx_ffe = max(tx_ffe, drm_dp_get_adjust_tx_ffe_preset(link_status, lane));
+ }
+
+ return tx_ffe;
+}
+
+/* 8b/10b */
+static u8 intel_dp_get_lane_adjust_vswing_preemph(struct intel_dp *intel_dp,
+ const struct intel_crtc_state *crtc_state,
+ enum drm_dp_phy dp_phy,
+ const u8 link_status[DP_LINK_STATUS_SIZE],
+ int lane)
{
u8 v = 0;
u8 p = 0;
@@ -340,6 +362,20 @@ static u8 intel_dp_get_lane_adjust_train(struct intel_dp *intel_dp,
return v | p;
}

+static u8 intel_dp_get_lane_adjust_train(struct intel_dp *intel_dp,
+ const struct intel_crtc_state *crtc_state,
+ enum drm_dp_phy dp_phy,
+ const u8 link_status[DP_LINK_STATUS_SIZE],
+ int lane)
+{
+ if (intel_dp_is_uhbr(crtc_state))
+ return intel_dp_get_lane_adjust_tx_ffe_preset(intel_dp, crtc_state,
+ dp_phy, link_status, lane);
+ else
+ return intel_dp_get_lane_adjust_vswing_preemph(intel_dp, crtc_state,
+ dp_phy, link_status, lane);
+}
+
#define TRAIN_REQ_FMT "%d/%d/%d/%d"
#define _TRAIN_REQ_VSWING_ARGS(link_status, lane) \
(drm_dp_get_adjust_request_voltage((link_status), (lane)) >> DP_TRAIN_VOLTAGE_SWING_SHIFT)
@@ -355,6 +391,13 @@ static u8 intel_dp_get_lane_adjust_train(struct intel_dp *intel_dp,
_TRAIN_REQ_PREEMPH_ARGS(link_status, 1), \
_TRAIN_REQ_PREEMPH_ARGS(link_status, 2), \
_TRAIN_REQ_PREEMPH_ARGS(link_status, 3)
+#define _TRAIN_REQ_TX_FFE_ARGS(link_status, lane) \
+ drm_dp_get_adjust_tx_ffe_preset((link_status), (lane))
+#define TRAIN_REQ_TX_FFE_ARGS(link_status) \
+ _TRAIN_REQ_TX_FFE_ARGS(link_status, 0), \
+ _TRAIN_REQ_TX_FFE_ARGS(link_status, 1), \
+ _TRAIN_REQ_TX_FFE_ARGS(link_status, 2), \
+ _TRAIN_REQ_TX_FFE_ARGS(link_status, 3)

void
intel_dp_get_adjust_train(struct intel_dp *intel_dp,
@@ -367,14 +410,23 @@ intel_dp_get_adjust_train(struct intel_dp *intel_dp,
char phy_name[10];
int lane;

- drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s][%s] lanes: %d, "
- "vswing request: " TRAIN_REQ_FMT ", "
- "pre-emphasis request: " TRAIN_REQ_FMT "\n",
- encoder->base.base.id, encoder->base.name,
- intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)),
- crtc_state->lane_count,
- TRAIN_REQ_VSWING_ARGS(link_status),
- TRAIN_REQ_PREEMPH_ARGS(link_status));
+ if (intel_dp_is_uhbr(crtc_state)) {
+ drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s][%s] 128b/132b, lanes: %d, "
+ "TX FFE request: " TRAIN_REQ_FMT "\n",
+ encoder->base.base.id, encoder->base.name,
+ intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)),
+ crtc_state->lane_count,
+ TRAIN_REQ_TX_FFE_ARGS(link_status));
+ } else {
+ drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s][%s] 8b/10b, lanes: %d, "
+ "vswing request: " TRAIN_REQ_FMT ", "
+ "pre-emphasis request: " TRAIN_REQ_FMT "\n",
+ encoder->base.base.id, encoder->base.name,
+ intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)),
+ crtc_state->lane_count,
+ TRAIN_REQ_VSWING_ARGS(link_status),
+ TRAIN_REQ_PREEMPH_ARGS(link_status));
+ }

for (lane = 0; lane < 4; lane++)
intel_dp->train_set[lane] =
@@ -464,6 +516,13 @@ intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
_TRAIN_SET_PREEMPH_ARGS((train_set)[1]), \
_TRAIN_SET_PREEMPH_ARGS((train_set)[2]), \
_TRAIN_SET_PREEMPH_ARGS((train_set)[3])
+#define _TRAIN_SET_TX_FFE_ARGS(train_set) \
+ ((train_set) & DP_TX_FFE_PRESET_VALUE_MASK), ""
+#define TRAIN_SET_TX_FFE_ARGS(train_set) \
+ _TRAIN_SET_TX_FFE_ARGS((train_set)[0]), \
+ _TRAIN_SET_TX_FFE_ARGS((train_set)[1]), \
+ _TRAIN_SET_TX_FFE_ARGS((train_set)[2]), \
+ _TRAIN_SET_TX_FFE_ARGS((train_set)[3])

void intel_dp_set_signal_levels(struct intel_dp *intel_dp,
const struct intel_crtc_state *crtc_state,
@@ -473,14 +532,23 @@ void intel_dp_set_signal_levels(struct intel_dp *intel_dp,
struct drm_i915_private *i915 = to_i915(encoder->base.dev);
char phy_name[10];

- drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s][%s] lanes: %d, "
- "vswing levels: " TRAIN_SET_FMT ", "
- "pre-emphasis levels: " TRAIN_SET_FMT "\n",
- encoder->base.base.id, encoder->base.name,
- intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)),
- crtc_state->lane_count,
- TRAIN_SET_VSWING_ARGS(intel_dp->train_set),
- TRAIN_SET_PREEMPH_ARGS(intel_dp->train_set));
+ if (intel_dp_is_uhbr(crtc_state)) {
+ drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s][%s] 128b/132b, lanes: %d, "
+ "TX FFE presets: " TRAIN_SET_FMT "\n",
+ encoder->base.base.id, encoder->base.name,
+ intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)),
+ crtc_state->lane_count,
+ TRAIN_SET_TX_FFE_ARGS(intel_dp->train_set));
+ } else {
+ drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s][%s] 8b/10b, lanes: %d, "
+ "vswing levels: " TRAIN_SET_FMT ", "
+ "pre-emphasis levels: " TRAIN_SET_FMT "\n",
+ encoder->base.base.id, encoder->base.name,
+ intel_dp_phy_name(dp_phy, phy_name, sizeof(phy_name)),
+ crtc_state->lane_count,
+ TRAIN_SET_VSWING_ARGS(intel_dp->train_set),
+ TRAIN_SET_PREEMPH_ARGS(intel_dp->train_set));
+ }

if (intel_dp_phy_is_downstream_of_source(intel_dp, dp_phy))
encoder->set_signal_levels(encoder, crtc_state);
@@ -515,7 +583,16 @@ intel_dp_update_link_train(struct intel_dp *intel_dp,
return ret == crtc_state->lane_count;
}

+/* 128b/132b */
+static bool intel_dp_lane_max_tx_ffe_reached(u8 train_set_lane)
+{
+ return (train_set_lane & DP_TX_FFE_PRESET_VALUE_MASK) ==
+ DP_TX_FFE_PRESET_VALUE_MASK;
+}
+
/*
+ * 8b/10b
+ *
* FIXME: The DP spec is very confusing here, also the Link CTS spec seems to
* have self contradicting tests around this area.
*
@@ -545,8 +622,15 @@ static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp,
int lane;

for (lane = 0; lane < crtc_state->lane_count; lane++) {
- if (!intel_dp_lane_max_vswing_reached(intel_dp->train_set[lane]))
- return false;
+ u8 train_set_lane = intel_dp->train_set[lane];
+
+ if (intel_dp_is_uhbr(crtc_state)) {
+ if (!intel_dp_lane_max_tx_ffe_reached(train_set_lane))
+ return false;
+ } else {
+ if (!intel_dp_lane_max_vswing_reached(train_set_lane))
+ return false;
+ }
}

return true;
@@ -609,17 +693,24 @@ static void intel_dp_link_training_clock_recovery_delay(struct intel_dp *intel_d
drm_dp_lttpr_link_train_clock_recovery_delay();
}

-static bool intel_dp_adjust_request_changed(int lane_count,
+static bool intel_dp_adjust_request_changed(const struct intel_crtc_state *crtc_state,
const u8 old_link_status[DP_LINK_STATUS_SIZE],
const u8 new_link_status[DP_LINK_STATUS_SIZE])
{
int lane;

- for (lane = 0; lane < lane_count; lane++) {
- u8 old = drm_dp_get_adjust_request_voltage(old_link_status, lane) |
- drm_dp_get_adjust_request_pre_emphasis(old_link_status, lane);
- u8 new = drm_dp_get_adjust_request_voltage(new_link_status, lane) |
- drm_dp_get_adjust_request_pre_emphasis(new_link_status, lane);
+ for (lane = 0; lane < crtc_state->lane_count; lane++) {
+ u8 old, new;
+
+ if (intel_dp_is_uhbr(crtc_state)) {
+ old = drm_dp_get_adjust_tx_ffe_preset(old_link_status, lane);
+ new = drm_dp_get_adjust_tx_ffe_preset(new_link_status, lane);
+ } else {
+ old = drm_dp_get_adjust_request_voltage(old_link_status, lane) |
+ drm_dp_get_adjust_request_pre_emphasis(old_link_status, lane);
+ new = drm_dp_get_adjust_request_voltage(new_link_status, lane) |
+ drm_dp_get_adjust_request_pre_emphasis(new_link_status, lane);
+ }

if (old != new)
return true;
@@ -729,8 +820,7 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp,
return false;
}

- if (!intel_dp_adjust_request_changed(crtc_state->lane_count,
- old_link_status, link_status))
+ if (!intel_dp_adjust_request_changed(crtc_state, old_link_status, link_status))
++voltage_tries;
else
voltage_tries = 1;
--
2.30.2