[PATCH] drm/i915: Add delay when checking link status

[Mika Kahola]

When we receive short hotplug detection we try to do link training twice
with the same voltage swing and pre-emphasis values. When we check link
status we realize that channel equalization is not ok and we retrain the
link. However, we end up retraining the link with the very same parameters
as we did in the first time. This patch introduces a small 1ms delay to let
things settle before we go and check the status of DP link.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100367
Signed-off-by: Mika Kahola <mika.kahola at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index bca4ac1..badd631 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4331,6 +4331,9 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
 			DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
 	}
 
+	/* give ~1ms time before checking link status */
+	usleep_range(1000, 1100);
+
 	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 	intel_dp_check_link_status(intel_dp);
 	drm_modeset_unlock(&dev->mode_config.connection_mutex);
-- 
2.7.4