From 0d71068835e2610576d369d6d4cbf90e0f802a71 Mon Sep 17 00:00:00 2001 From: Paulo Zanoni Date: Fri, 29 Jun 2012 16:03:34 -0300 Subject: [PATCH] drm/i915: try to train DP even harder While debugging Haswell link train failures I observed that we never try the maximum voltage configuration more than once consecutively. We start the training, the monitor keeps telling us to increase the voltage, then when we reach the maximum we just go back to the start (because of the "memset" above "voltage_tries = 0"). When we reach this point, we keep alternating between the maximum and the minimum voltages until we give up. The DP spec suggests that we should try the same voltage 5 times before giving up. This patch makes us try the maximum voltage at least 5 times before going back to the minimum voltages. This patch does not fix any particular bug I'm aware of. Signed-off-by: Paulo Zanoni Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/intel_dp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 2bc1505132c3..0a56b9ab0f58 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -1771,7 +1771,7 @@ intel_dp_start_link_train(struct intel_dp *intel_dp) for (i = 0; i < intel_dp->lane_count; i++) if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0) break; - if (i == intel_dp->lane_count) { + if (i == intel_dp->lane_count && voltage_tries == 5) { ++loop_tries; if (loop_tries == 5) { DRM_DEBUG_KMS("too many full retries, give up\n"); -- 2.20.1