[PATCH v2 04/21] drm/i915/dp: Sanitize intel_dp_get_link_train_fallback_values()

Imre Deak
2024-05-20T18:58:34Z

Reduce the indentation in intel_dp_get_link_train_fallback_values() by
adding separate helpers to reduce the link rate and lane count. Also
simplify things by passing crtc_state to the function.

This also prepares for later patches in the patchset adding a limitation
on how the link params are reduced.

Signed-off-by: Imre Deak <imre.deak@intel.com>
---
.../drm/i915/display/intel_dp_link_training.c | 82 ++++++++++++-------
1 file changed, 51 insertions(+), 31 deletions(-)

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 4db293f256896..edc970036866a 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -1109,11 +1109,37 @@ static bool intel_dp_can_link_train_fallback_for_edp(struct intel_dp *intel_dp,
return true;
}

+static int reduce_link_rate(struct intel_dp *intel_dp, int current_rate)
+{
+ int rate_index;
+ int new_rate;
+
+ rate_index = intel_dp_rate_index(intel_dp->common_rates,
+ intel_dp->num_common_rates,
+ current_rate);
+
+ if (rate_index <= 0)
+ return -1;
+
+ new_rate = intel_dp_common_rate(intel_dp, rate_index - 1);
+
+ return new_rate;
+}
+
+static int reduce_lane_count(struct intel_dp *intel_dp, int current_lane_count)
+{
+ if (current_lane_count > 1)
+ return current_lane_count >> 1;
+
+ return -1;
+}
+
static int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
- int link_rate, u8 lane_count)
+ const struct intel_crtc_state *crtc_state)
{
struct drm_i915_private *i915 = dp_to_i915(intel_dp);
- int index;
+ int new_link_rate;
+ int new_lane_count;

/*
* TODO: Enable fallback on MST links once MST link compute can handle
@@ -1131,36 +1157,32 @@ static int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
return 0;
}

- index = intel_dp_rate_index(intel_dp->common_rates,
- intel_dp->num_common_rates,
- link_rate);
- if (index > 0) {
- if (intel_dp_is_edp(intel_dp) &&
- !intel_dp_can_link_train_fallback_for_edp(intel_dp,
- intel_dp_common_rate(intel_dp, index - 1),
- lane_count)) {
- drm_dbg_kms(&i915->drm,
- "Retrying Link training for eDP with same parameters\n");
- return 0;
- }
- intel_dp->link.max_rate = intel_dp_common_rate(intel_dp, index - 1);
- intel_dp->link.max_lane_count = lane_count;
- } else if (lane_count > 1) {
- if (intel_dp_is_edp(intel_dp) &&
- !intel_dp_can_link_train_fallback_for_edp(intel_dp,
- intel_dp_max_common_rate(intel_dp),
- lane_count >> 1)) {
- drm_dbg_kms(&i915->drm,
- "Retrying Link training for eDP with same parameters\n");
- return 0;
- }
- intel_dp->link.max_rate = intel_dp_max_common_rate(intel_dp);
- intel_dp->link.max_lane_count = lane_count >> 1;
- } else {
+ new_lane_count = crtc_state->lane_count;
+ new_link_rate = reduce_link_rate(intel_dp, crtc_state->port_clock);
+ if (new_link_rate < 0) {
+ new_lane_count = reduce_lane_count(intel_dp, crtc_state->lane_count);
+ new_link_rate = intel_dp_max_common_rate(intel_dp);
+ }
+
+ if (new_lane_count < 0) {
drm_err(&i915->drm, "Link Training Unsuccessful\n");
return -1;
}

+ if (intel_dp_is_edp(intel_dp) &&
+ !intel_dp_can_link_train_fallback_for_edp(intel_dp, new_link_rate, new_lane_count)) {
+ drm_dbg_kms(&i915->drm,
+ "Retrying Link training for eDP with same parameters\n");
+ return 0;
+ }
+
+ drm_dbg_kms(&i915->drm, "Reducing link parameters from %dx%d to %dx%d\n",
+ crtc_state->lane_count, crtc_state->port_clock,
+ new_lane_count, new_link_rate);
+
+ intel_dp->link.max_rate = new_link_rate;
+ intel_dp->link.max_lane_count = new_lane_count;
+
return 0;
}

@@ -1178,9 +1200,7 @@ static void intel_dp_schedule_fallback_link_training(struct intel_dp *intel_dp,
lt_dbg(intel_dp, DP_PHY_DPRX,
"Link Training failed with HOBL active, not enabling it from now on\n");
intel_dp->hobl_failed = true;
- } else if (intel_dp_get_link_train_fallback_values(intel_dp,
- crtc_state->port_clock,
- crtc_state->lane_count)) {
+ } else if (intel_dp_get_link_train_fallback_values(intel_dp, crtc_state)) {
return;
}

--
2.43.3