thunderbolt: Introduce tb_port_reset()

Introduce a function that issues Downstream Port Reset to a USB4 port.
This supports Thunderbolt 2, 3 and USB4 routers.

Signed-off-by: Sanath S <Sanath.S@amd.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
index f8f0d24ff6e4..4b35898aa216 100644
--- a/drivers/thunderbolt/usb4.c
+++ b/drivers/thunderbolt/usb4.c
@@ -1113,6 +1113,45 @@ int usb4_port_hotplug_enable(struct tb_port *port)
 	return tb_port_write(port, &val, TB_CFG_PORT, ADP_CS_5, 1);
 }
 
+/**
+ * usb4_port_reset() - Issue downstream port reset
+ * @port: USB4 port to reset
+ *
+ * Issues downstream port reset to @port.
+ */
+int usb4_port_reset(struct tb_port *port)
+{
+	int ret;
+	u32 val;
+
+	if (!port->cap_usb4)
+		return -EINVAL;
+
+	ret = tb_port_read(port, &val, TB_CFG_PORT,
+			   port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
+
+	val |= PORT_CS_19_DPR;
+
+	ret = tb_port_write(port, &val, TB_CFG_PORT,
+			    port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
+
+	fsleep(10000);
+
+	ret = tb_port_read(port, &val, TB_CFG_PORT,
+			   port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
+
+	val &= ~PORT_CS_19_DPR;
+
+	return tb_port_write(port, &val, TB_CFG_PORT,
+			     port->cap_usb4 + PORT_CS_19, 1);
+}
+
 static int usb4_port_set_configured(struct tb_port *port, bool configured)
 {
 	int ret;