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 <[email protected]> Cc: Rodrigo Vivi <[email protected]> Cc: Marc Herbert <[email protected]> Suggested-by: Marc Herbert <[email protected]> Signed-off-by: Nathan Ciobanu <[email protected]> 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 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
