thunderbolt: Use scale field when allocating USB3 bandwidth

When tunneling aggregated USB3 (20 Gb/s) the bandwidth values that are
programmed to the ADP_USB3_CS_2 go higher than 4096 and that does not
fit anymore to the 12-bit field. Fix this by scaling the value using
the scale field accordingly.

Fixes: 3b1d8d57 ("thunderbolt: Implement USB3 bandwidth negotiation routines")
Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/usb4.c

@@ -2094,18 +2094,30 @@ static int usb4_usb3_port_write_allocated_bandwidth(struct tb_port *port,
 						    int downstream_bw)
 {
 	u32 val, ubw, dbw, scale;
-	int ret;
+	int ret, max_bw;
 
-	/* Read the used scale, hardware default is 0 */
-	ret = tb_port_read(port, &scale, TB_CFG_PORT,
-			   port->cap_adap + ADP_USB3_CS_3, 1);
+	/* Figure out suitable scale */
+	scale = 0;
+	max_bw = max(upstream_bw, downstream_bw);
+	while (scale < 64) {
+		if (mbps_to_usb3_bw(max_bw, scale) < 4096)
+			break;
+		scale++;
+	}
+
+	if (WARN_ON(scale >= 64))
+		return -EINVAL;
+
+	ret = tb_port_write(port, &scale, TB_CFG_PORT,
+			    port->cap_adap + ADP_USB3_CS_3, 1);
 	if (ret)
 		return ret;
 
-	scale &= ADP_USB3_CS_3_SCALE_MASK;
 	ubw = mbps_to_usb3_bw(upstream_bw, scale);
 	dbw = mbps_to_usb3_bw(downstream_bw, scale);
 
+	tb_port_dbg(port, "scaled bandwidth %u/%u, scale %u\n", ubw, dbw, scale);
+
 	ret = tb_port_read(port, &val, TB_CFG_PORT,
 			   port->cap_adap + ADP_USB3_CS_2, 1);
 	if (ret)