drm/dp: Make sink count DP 1.2 aware

Signed-off-by: NAdam Jackson <ajax@redhat.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -2101,13 +2101,12 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 	/* If we're HPD-aware, SINK_COUNT changes dynamically */
 	hpd = !!(intel_dp->downstream_ports[0] & DP_DS_PORT_HPD);
 	if (hpd) {
-		uint8_t sink_count;
+		uint8_t reg;
 		if (!intel_dp_aux_native_read_retry(intel_dp, DP_SINK_COUNT,
-						    &sink_count, 1))
+						    &reg, 1))
 			return connector_status_unknown;
-		sink_count &= DP_SINK_COUNT_MASK;
-		return sink_count ? connector_status_connected
-				  : connector_status_disconnected;
+		return DP_GET_SINK_COUNT(reg) ? connector_status_connected
+					      : connector_status_disconnected;
 	}
 
 	/* If no HPD, poke DDC gently */

include/drm/drm_dp_helper.h

@@ -221,7 +221,8 @@
 # define DP_PSR_FRAME_CAPTURE		    (1 << 3)
 
 #define DP_SINK_COUNT			    0x200
-# define DP_SINK_COUNT_MASK		    (31 << 0)
+/* prior to 1.2 bit 7 was reserved mbz */
+# define DP_GET_SINK_COUNT(x)		    ((((x) & 0x80) >> 1) | ((x) & 0x3f))
 # define DP_SINK_CP_READY		    (1 << 6)
 
 #define DP_DEVICE_SERVICE_IRQ_VECTOR	    0x201