thunderbolt: Make is_gen4_link() available to the rest of the driver

Rework the function to return the link generation, update the name to
tb_port_get_link_generation(), and make available to the rest of the
driver. This is needed in the subsequent patches.
Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/switch.c

@@ -915,6 +915,32 @@ int tb_port_get_link_speed(struct tb_port *port)
 	}
 }
 
+/**
+ * tb_port_get_link_generation() - Returns link generation
+ * @port: Lane adapter
+ *
+ * Returns link generation as number or negative errno in case of
+ * failure. Does not distinguish between Thunderbolt 1 and Thunderbolt 2
+ * links so for those always returns 2.
+ */
+int tb_port_get_link_generation(struct tb_port *port)
+{
+	int ret;
+
+	ret = tb_port_get_link_speed(port);
+	if (ret < 0)
+		return ret;
+
+	switch (ret) {
+	case 40:
+		return 4;
+	case 20:
+		return 3;
+	default:
+		return 2;
+	}
+}
+
 /**
  * tb_port_get_link_width() - Get current link width
  * @port: Port to check (USB4 or CIO)
@@ -960,11 +986,6 @@ static bool tb_port_is_width_supported(struct tb_port *port,
 	return widths & width_mask;
 }
 
-static bool is_gen4_link(struct tb_port *port)
-{
-	return tb_port_get_link_speed(port) > 20;
-}
-
 /**
  * tb_port_set_link_width() - Set target link width of the lane adapter
  * @port: Lane adapter
@@ -992,7 +1013,7 @@ int tb_port_set_link_width(struct tb_port *port, enum tb_link_width width)
 	switch (width) {
 	case TB_LINK_WIDTH_SINGLE:
 		/* Gen 4 link cannot be single */
-		if (is_gen4_link(port))
+		if (tb_port_get_link_generation(port) >= 4)
 			return -EOPNOTSUPP;
 		val |= LANE_ADP_CS_1_TARGET_WIDTH_SINGLE <<
 			LANE_ADP_CS_1_TARGET_WIDTH_SHIFT;
@@ -1141,7 +1162,8 @@ int tb_port_wait_for_link_width(struct tb_port *port, unsigned int width_mask,
 	int ret;
 
 	/* Gen 4 link does not support single lane */
-	if ((width_mask & TB_LINK_WIDTH_SINGLE) && is_gen4_link(port))
+	if ((width_mask & TB_LINK_WIDTH_SINGLE) &&
+	    tb_port_get_link_generation(port) >= 4)
 		return -EOPNOTSUPP;
 
 	do {

drivers/thunderbolt/tb.h

@@ -1057,6 +1057,7 @@ static inline bool tb_port_use_credit_allocation(const struct tb_port *port)
 	     (p) = tb_next_port_on_path((src), (dst), (p)))
 
 int tb_port_get_link_speed(struct tb_port *port);
+int tb_port_get_link_generation(struct tb_port *port);
 int tb_port_get_link_width(struct tb_port *port);
 int tb_port_set_link_width(struct tb_port *port, enum tb_link_width width);
 int tb_port_lane_bonding_enable(struct tb_port *port);