[Intel-gfx] [PATCH v2 2/6] drm/i915: Simplify the link training functions
Imre Deak
imre.deak at intel.com
Thu Sep 24 18:48:01 UTC 2020
Split the prepare, link training, fallback-handling steps into their own
functions for clarity and as a preparation for the upcoming LTTPR
changes.
While at it also:
- Unexport and inline intel_dp_set_idle_link_train(), which is used at a
single place.
- Add some documentation to functions that are exported or that can use
a better description about which part of the LT sequence they
implement.
v2: (Ville)
- Unexport/inline intel_dp_set_idle_link_train()
- Make the documentation of
intel_dp_prepare_link_train()/intel_dp_stop_link_train() more accurate
wrt. HW specific details.
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
drivers/gpu/drm/i915/display/intel_dp.c | 6 --
drivers/gpu/drm/i915/display/intel_dp.h | 1 -
.../drm/i915/display/intel_dp_link_training.c | 90 ++++++++++++++-----
3 files changed, 70 insertions(+), 27 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index bba9669e0e57..b21f42193a11 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4508,12 +4508,6 @@ intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
intel_dp->set_link_train(intel_dp, dp_train_pat);
}
-void intel_dp_set_idle_link_train(struct intel_dp *intel_dp)
-{
- if (intel_dp->set_idle_link_train)
- intel_dp->set_idle_link_train(intel_dp);
-}
-
static void
intel_dp_link_down(struct intel_encoder *encoder,
const struct intel_crtc_state *old_crtc_state)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
index 08a1c0aa8b94..ca8319d6c63c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -95,7 +95,6 @@ intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
u8 dp_train_pat);
void
intel_dp_set_signal_levels(struct intel_dp *intel_dp);
-void intel_dp_set_idle_link_train(struct intel_dp *intel_dp);
void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
u8 *link_bw, u8 *rate_select);
bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
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 0e1472b1f868..78b0f165fadd 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -146,14 +146,13 @@ static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
return true;
}
-/* Enable corresponding port and start training pattern 1 */
-static bool
-intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
+/*
+ * Prepare link training by configuring the link parameters. On DDI platforms
+ * also enable the port here.
+ */
+static void intel_dp_prepare_link_train(struct intel_dp *intel_dp)
{
struct drm_i915_private *i915 = dp_to_i915(intel_dp);
- u8 voltage;
- int voltage_tries, cr_tries, max_cr_tries;
- bool max_vswing_reached = false;
u8 link_config[2];
u8 link_bw, rate_select;
@@ -187,6 +186,16 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
intel_dp->DP |= DP_PORT_EN;
+}
+
+/* Perform the link training clock recovery phase using training pattern 1. */
+static bool
+intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
+{
+ struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+ u8 voltage;
+ int voltage_tries, cr_tries, max_cr_tries;
+ bool max_vswing_reached = false;
/* clock recovery */
if (!intel_dp_reset_link_train(intel_dp,
@@ -309,6 +318,10 @@ static u32 intel_dp_training_pattern(struct intel_dp *intel_dp)
return DP_TRAINING_PATTERN_2;
}
+/*
+ * Perform the link training channel equalization phase using one of training
+ * pattern 2, 3 or 4 depending on the source and sink capabilities.
+ */
static bool
intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
{
@@ -373,12 +386,27 @@ intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
"Channel equalization failed 5 times\n");
}
- intel_dp_set_idle_link_train(intel_dp);
+ if (intel_dp->set_idle_link_train)
+ intel_dp->set_idle_link_train(intel_dp);
return channel_eq;
-
}
+/**
+ * intel_dp_stop_link_train - stop link training
+ * @intel_dp: DP struct
+ *
+ * Stop the link training of the @intel_dp port, disabling the test pattern
+ * symbol generation on the port and disabling the training pattern in
+ * the sink's DPCD.
+ *
+ * What symbols are output on the port after this point is
+ * platform specific: On DDI/VLV/CHV platforms it will be the idle pattern
+ * with the pipe being disabled, on older platforms it's HW specific if/how an
+ * idle pattern is generated, as the pipe is already enabled here for those.
+ *
+ * This function must be called after intel_dp_start_link_train().
+ */
void intel_dp_stop_link_train(struct intel_dp *intel_dp)
{
intel_dp->link_trained = true;
@@ -387,30 +415,37 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
DP_TRAINING_PATTERN_DISABLE);
}
-void
-intel_dp_start_link_train(struct intel_dp *intel_dp)
+static bool
+intel_dp_link_train(struct intel_dp *intel_dp)
{
struct intel_connector *intel_connector = intel_dp->attached_connector;
+ bool ret = false;
+
+ intel_dp_prepare_link_train(intel_dp);
if (!intel_dp_link_training_clock_recovery(intel_dp))
- goto failure_handling;
+ goto out;
+
if (!intel_dp_link_training_channel_equalization(intel_dp))
- goto failure_handling;
+ goto out;
- drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
- "[CONNECTOR:%d:%s] Link Training Passed at Link Rate = %d, Lane count = %d",
- intel_connector->base.base.id,
- intel_connector->base.name,
- intel_dp->link_rate, intel_dp->lane_count);
- return;
+ ret = true;
- failure_handling:
+out:
drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
- "[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
+ "[CONNECTOR:%d:%s] Link Training %s at Link Rate = %d, Lane count = %d",
intel_connector->base.base.id,
intel_connector->base.name,
+ ret ? "passed" : "failed",
intel_dp->link_rate, intel_dp->lane_count);
+ return ret;
+}
+
+static void intel_dp_schedule_fallback_link_training(struct intel_dp *intel_dp)
+{
+ struct intel_connector *intel_connector = intel_dp->attached_connector;
+
if (intel_dp->hobl_active) {
drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
"Link Training failed with HOBL active, not enabling it from now on");
@@ -424,3 +459,18 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
/* Schedule a Hotplug Uevent to userspace to start modeset */
schedule_work(&intel_connector->modeset_retry_work);
}
+
+/**
+ * intel_dp_start_link_train - start link training
+ * @intel_dp: DP struct
+ *
+ * Start the link training of the @intel_dp port, scheduling a fallback
+ * retraining with reduced link rate/lane parameters if the link training
+ * fails.
+ * After calling this function intel_dp_stop_link_train() must be called.
+ */
+void intel_dp_start_link_train(struct intel_dp *intel_dp)
+{
+ if (!intel_dp_link_train(intel_dp))
+ intel_dp_schedule_fallback_link_training(intel_dp);
+}
--
2.25.1
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