thunderbolt: Use DP_LOCAL_CAP for maximum bandwidth calculation

The DisplayPort IN adapter DP_LOCAL_CAP holds the aggregated
capabilities and gets updated after graphics side does the DPRX
capabilities read so we should use this to figure out the maximum
possible bandwidth for the DisplayPort tunnel.

While there make the variable name to match better what it is used for
and add kernel-doc comment to the function.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/tunnel.c

@@ -926,12 +926,18 @@ static int tb_dp_activate(struct tb_tunnel *tunnel, bool active)
 	return 0;
 }
 
-/* max_bw is rounded up to next granularity */
+/**
+ * tb_dp_bandwidth_mode_maximum_bandwidth() - Maximum possible bandwidth
+ * @tunnel: DP tunnel to check
+ * @max_bw_rounded: Maximum bandwidth in Mb/s rounded up to the next granularity
+ *
+ * Returns maximum possible bandwidth for this tunnel in Mb/s.
+ */
 static int tb_dp_bandwidth_mode_maximum_bandwidth(struct tb_tunnel *tunnel,
-						  int *max_bw)
+						  int *max_bw_rounded)
 {
 	struct tb_port *in = tunnel->src_port;
-	int ret, rate, lanes, nrd_bw;
+	int ret, rate, lanes, max_bw;
 	u32 cap;
 
 	/*
@@ -947,32 +953,18 @@ static int tb_dp_bandwidth_mode_maximum_bandwidth(struct tb_tunnel *tunnel,
 		return ret;
 
 	rate = tb_dp_cap_get_rate_ext(cap);
-	if (tb_dp_is_uhbr_rate(rate)) {
-		/*
-		 * When UHBR is used there is no reduction in lanes so
-		 * we can use this directly.
-		 */
-		lanes = tb_dp_cap_get_lanes(cap);
-	} else {
-		/*
-		 * If there is no UHBR supported then check the
-		 * non-reduced rate and lanes.
-		 */
-		ret = usb4_dp_port_nrd(in, &rate, &lanes);
-		if (ret)
-			return ret;
-	}
+	lanes = tb_dp_cap_get_lanes(cap);
 
-	nrd_bw = tb_dp_bandwidth(rate, lanes);
+	max_bw = tb_dp_bandwidth(rate, lanes);
 
-	if (max_bw) {
+	if (max_bw_rounded) {
 		ret = usb4_dp_port_granularity(in);
 		if (ret < 0)
 			return ret;
-		*max_bw = roundup(nrd_bw, ret);
+		*max_bw_rounded = roundup(max_bw, ret);
 	}
 
-	return nrd_bw;
+	return max_bw;
 }
 
 static int tb_dp_bandwidth_mode_consumed_bandwidth(struct tb_tunnel *tunnel,
@@ -981,7 +973,7 @@ static int tb_dp_bandwidth_mode_consumed_bandwidth(struct tb_tunnel *tunnel,
 {
 	struct tb_port *out = tunnel->dst_port;
 	struct tb_port *in = tunnel->src_port;
-	int ret, allocated_bw, max_bw;
+	int ret, allocated_bw, max_bw_rounded;
 
 	if (!usb4_dp_port_bandwidth_mode_enabled(in))
 		return -EOPNOTSUPP;
@@ -995,10 +987,10 @@ static int tb_dp_bandwidth_mode_consumed_bandwidth(struct tb_tunnel *tunnel,
 		return ret;
 	allocated_bw = ret;
 
-	ret = tb_dp_bandwidth_mode_maximum_bandwidth(tunnel, &max_bw);
+	ret = tb_dp_bandwidth_mode_maximum_bandwidth(tunnel, &max_bw_rounded);
 	if (ret < 0)
 		return ret;
-	if (allocated_bw == max_bw)
+	if (allocated_bw == max_bw_rounded)
 		allocated_bw = ret;
 
 	if (tb_port_path_direction_downstream(in, out)) {
@@ -1023,17 +1015,18 @@ static int tb_dp_allocated_bandwidth(struct tb_tunnel *tunnel, int *allocated_up
 	 * Otherwise we read it from the DPRX.
 	 */
 	if (usb4_dp_port_bandwidth_mode_enabled(in) && tunnel->bw_mode) {
-		int ret, allocated_bw, max_bw;
+		int ret, allocated_bw, max_bw_rounded;
 
 		ret = usb4_dp_port_allocated_bandwidth(in);
 		if (ret < 0)
 			return ret;
 		allocated_bw = ret;
 
-		ret = tb_dp_bandwidth_mode_maximum_bandwidth(tunnel, &max_bw);
+		ret = tb_dp_bandwidth_mode_maximum_bandwidth(tunnel,
+							     &max_bw_rounded);
 		if (ret < 0)
 			return ret;
-		if (allocated_bw == max_bw)
+		if (allocated_bw == max_bw_rounded)
 			allocated_bw = ret;
 
 		if (tb_port_path_direction_downstream(in, out)) {
@@ -1055,24 +1048,24 @@ static int tb_dp_alloc_bandwidth(struct tb_tunnel *tunnel, int *alloc_up,
 {
 	struct tb_port *out = tunnel->dst_port;
 	struct tb_port *in = tunnel->src_port;
-	int max_bw, ret, tmp;
+	int max_bw_rounded, ret, tmp;
 
 	if (!usb4_dp_port_bandwidth_mode_enabled(in))
 		return -EOPNOTSUPP;
 
-	ret = tb_dp_bandwidth_mode_maximum_bandwidth(tunnel, &max_bw);
+	ret = tb_dp_bandwidth_mode_maximum_bandwidth(tunnel, &max_bw_rounded);
 	if (ret < 0)
 		return ret;
 
 	if (tb_port_path_direction_downstream(in, out)) {
-		tmp = min(*alloc_down, max_bw);
+		tmp = min(*alloc_down, max_bw_rounded);
 		ret = usb4_dp_port_allocate_bandwidth(in, tmp);
 		if (ret)
 			return ret;
 		*alloc_down = tmp;
 		*alloc_up = 0;
 	} else {
-		tmp = min(*alloc_up, max_bw);
+		tmp = min(*alloc_up, max_bw_rounded);
 		ret = usb4_dp_port_allocate_bandwidth(in, tmp);
 		if (ret)
 			return ret;