[PATCH 4/5] drm/i915/hdcp: Read Rxcaps for robustibility

[Suraj Kandpal]

We see some monitors and docks report incorrect hdcp version
and capability in first few reads so we read rx_caps three times
before we conclude the monitor's or docks HDCP capability

Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 22 ++++++++++++--------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
index 9161252ca4dd..5c41c54df6c2 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
@@ -656,20 +656,24 @@ int intel_dp_hdcp2_capable(struct intel_connector *connector,
 {
 	struct drm_dp_aux *aux;
 	u8 rx_caps[3];
-	int ret;
+	int ret, i;
 
 	aux = intel_dp_hdcp_get_aux(connector, true);
 
 	*capable = false;
-	ret = drm_dp_dpcd_read(aux,
-			       DP_HDCP_2_2_REG_RX_CAPS_OFFSET,
-			       rx_caps, HDCP_2_2_RXCAPS_LEN);
-	if (ret != HDCP_2_2_RXCAPS_LEN)
-		return ret >= 0 ? -EIO : ret;
+	for (i = 0; i < 3; i++) {
+		ret = drm_dp_dpcd_read(aux,
+				       DP_HDCP_2_2_REG_RX_CAPS_OFFSET,
+				       rx_caps, HDCP_2_2_RXCAPS_LEN);
+		if (ret != HDCP_2_2_RXCAPS_LEN)
+			return ret >= 0 ? -EIO : ret;
 
-	if (rx_caps[0] == HDCP_2_2_RX_CAPS_VERSION_VAL &&
-	    HDCP_2_2_DP_HDCP_CAPABLE(rx_caps[2]))
-		*capable = true;
+		if (rx_caps[0] == HDCP_2_2_RX_CAPS_VERSION_VAL &&
+		    HDCP_2_2_DP_HDCP_CAPABLE(rx_caps[2])) {
+			*capable = true;
+			break;
+		}
+	}
 
 	return 0;
 }
-- 
2.25.1