[Intel-gfx] [PATCH] drm/i915/dp: Poll for DDI Idle status to be 0 after enabling DDI Buf

[Manasi Navare]

The Bspec sequence expects us to poll for DDI Idle status
to be 0 (not idle) with a timeout of 600usecs after enabling the
DDI BUF CTL. But currently in the driver we just wait for 600usecs
without polling so add that.

Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
---
 drivers/gpu/drm/i915/display/intel_ddi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index ca7bb2294d2b..de7e15de0bc5 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -4023,7 +4023,11 @@ static void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp)
 	intel_de_write(dev_priv, DDI_BUF_CTL(port), intel_dp->DP);
 	intel_de_posting_read(dev_priv, DDI_BUF_CTL(port));
 
-	udelay(600);
+	if (wait_for_us(!(intel_de_read(dev_priv, DDI_BUF_CTL(port)) &
+			  DDI_BUF_IS_IDLE),
+			600))
+		drm_err(&dev_priv->drm, "DDI port:%c buffer idle\n",
+			port_name(port));
 }
 
 static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
-- 
2.19.1