Clarifies the clock recovery loop limit comment that 80
max_cr_tries for pre-DP1.4 devices was chosen as a very
tolerant upper bound.
Assumptions made:
- DP1.4 syncs should be smarter so they won't need more
than 10 tries
- pre-DP1.4 syncs should be compliant enough to not need
that many tries (80) but we should tolerate any that may
trigger this corner case
Cc: Dhinakaran Pandiyan <dhinakaran.pandi...@intel.com>
Cc: Rodrigo Vivi <rodrigo.v...@intel.com>
Cc: Marc Herbert <marc.herb...@intel.com>
Suggested-by: Marc Herbert <marc.herb...@intel.com>
Signed-off-by: Nathan Ciobanu <nathan.d.ciob...@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 07e128c7443c..a9f40985a621 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -172,10 +172,12 @@ static bool intel_dp_link_max_vswing_reached(struct
intel_dp *intel_dp)
}
/*
- * DP 1.4 spec clock recovery retries defined but
- * for devices pre-DP 1.4 we set the retry limit
- * to 4 (voltage levels) x 4 (preemphasis levels) x
- * x 5 (same voltage retries) = 80 (max iterations)
+ * The DP 1.4 spec defines the max clock recovery retries value
+ * as 10 but for pre-DP 1.4 devices we set a very tolerant
+ * retry limit of 80 (4 voltage levels x 4 preemphasis levels x
+ * x 5 identical voltage retries). Since the previous specs didn't
+ * define a limit and created the possibility of an infinite loop
+ * we want to prevent any sync from triggering that corner case.
*/
if (intel_dp->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
max_cr_tries = 10;
--
1.9.1
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