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Revert "drm/i915: Try harder to complete DP training pattern 1"
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This reverts commit 2477367.

If (for whatever reason) the DP sink device never asks for the maximal
voltage level, we never don't hit the check that should bail us out
after 5 retries of the same voltage. Which leads to an endless loop in
the DP link training code, which hangs the driver.

Now some more DP link training experiments on eDP panels seem to
indicate that our training algorithm isn't robust enough anyway and
needs more work. Hence for 3.7-fixes, let's just revert the regressing
commit instead of trying to apply more duct-tape.

Reported-by: Oleksij Rempel <bug-track@fisher-privat.net>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
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Daniel Vetter committed Oct 16, 2012
1 parent e751823 commit b06fbda
Showing 1 changed file with 10 additions and 5 deletions.
15 changes: 10 additions & 5 deletions drivers/gpu/drm/i915/intel_dp.c
Original file line number Diff line number Diff line change
Expand Up @@ -1798,7 +1798,8 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
break;
if (i == intel_dp->lane_count && voltage_tries == 5) {
if (++loop_tries == 5) {
++loop_tries;
if (loop_tries == 5) {
DRM_DEBUG_KMS("too many full retries, give up\n");
break;
}
Expand All @@ -1808,11 +1809,15 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
}

/* Check to see if we've tried the same voltage 5 times */
if ((intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK) != voltage) {
voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;
voltage_tries = 0;
} else
if ((intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK) == voltage) {
++voltage_tries;
if (voltage_tries == 5) {
DRM_DEBUG_KMS("too many voltage retries, give up\n");
break;
}
} else
voltage_tries = 0;
voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;

/* Compute new intel_dp->train_set as requested by target */
intel_get_adjust_train(intel_dp, link_status);
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