[Intel-gfx] [PATCH] drm/i915: preserve other DP_TEST_SINK bits.

[Rodrigo Vivi]

Sink crc was implemented based on dp 1.1 spec that had all TEST_SINK bits
reserved reading all 0s. But when reviewing my latest changes on sink crc
Todd warned me that on new specs we have other valid bits on this reg that we
might want to preserve.

Cc: Todd Previte <tprevite at gmail.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index b8699b0..7d5fa2f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3821,8 +3821,9 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
 	if (!(buf & DP_TEST_CRC_SUPPORTED))
 		return -ENOTTY;
 
+	drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf);
 	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK,
-			       DP_TEST_SINK_START) < 0)
+				buf | DP_TEST_SINK_START) < 0)
 		return -EIO;
 
 	drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC, &buf);
@@ -3841,7 +3842,10 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
 	if (drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_CRC_R_CR, crc, 6) < 0)
 		return -EIO;
 
-	drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK, 0);
+	drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf);
+	drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK,
+			buf & ~DP_TEST_SINK_START);
+
 	return 0;
 }
 
-- 
1.9.3