thunderbolt: Add missing UNSET_INBOUND_SBTX for retimer access

According to USB4 retimer specification, the process of firmware update
sequence requires issuing a SET_INBOUND_SBTX port operation that later
shall be followed by UNSET_INBOUND_SBTX port operation. This last step
is not currently issued by the driver but it is necessary to make sure
the retimers are put back to passthrough mode even during enumeration.

If this step is missing the link may not come up properly after
soft-reboot for example.

For this reason issue UNSET_INBOUND_SBTX after SET_INBOUND_SBTX for
enumeration and also when the NVM upgrade is run.

Reported-by: Christian Schaubschläger <[email protected]>
Link: https://lore.kernel.org/linux-usb/[email protected]/
Cc: [email protected]
Signed-off-by: Gil Fine <[email protected]>
Signed-off-by: Mika Westerberg <[email protected]>

Author: Gil Fine

drivers/thunderbolt/retimer.c

@@ -187,6 +187,22 @@ static ssize_t nvm_authenticate_show(struct device *dev,
 	return ret;
 }
 
+static void tb_retimer_set_inbound_sbtx(struct tb_port *port)
+{
+	int i;
+
+	for (i = 1; i <= TB_MAX_RETIMER_INDEX; i++)
+		usb4_port_retimer_set_inbound_sbtx(port, i);
+}
+
+static void tb_retimer_unset_inbound_sbtx(struct tb_port *port)
+{
+	int i;
+
+	for (i = TB_MAX_RETIMER_INDEX; i >= 1; i--)
+		usb4_port_retimer_unset_inbound_sbtx(port, i);
+}
+
 static ssize_t nvm_authenticate_store(struct device *dev,
 	struct device_attribute *attr, const char *buf, size_t count)
 {
@@ -213,6 +229,7 @@ static ssize_t nvm_authenticate_store(struct device *dev,
 	rt->auth_status = 0;
 
 	if (val) {
+		tb_retimer_set_inbound_sbtx(rt->port);
 		if (val == AUTHENTICATE_ONLY) {
 			ret = tb_retimer_nvm_authenticate(rt, true);
 		} else {
@@ -232,6 +249,7 @@ static ssize_t nvm_authenticate_store(struct device *dev,
 	}
 
 exit_unlock:
+	tb_retimer_unset_inbound_sbtx(rt->port);
 	mutex_unlock(&rt->tb->lock);
 exit_rpm:
 	pm_runtime_mark_last_busy(&rt->dev);
@@ -440,8 +458,7 @@ int tb_retimer_scan(struct tb_port *port, bool add)
 	 * Enable sideband channel for each retimer. We can do this
 	 * regardless whether there is device connected or not.
 	 */
-	for (i = 1; i <= TB_MAX_RETIMER_INDEX; i++)
-		usb4_port_retimer_set_inbound_sbtx(port, i);
+	tb_retimer_set_inbound_sbtx(port);
 
 	/*
 	 * Before doing anything else, read the authentication status.
@@ -464,6 +481,8 @@ int tb_retimer_scan(struct tb_port *port, bool add)
 			break;
 	}
 
+	tb_retimer_unset_inbound_sbtx(port);
+
 	if (!last_idx)
 		return 0;
 

drivers/thunderbolt/sb_regs.h

@@ -20,6 +20,7 @@ enum usb4_sb_opcode {
 	USB4_SB_OPCODE_ROUTER_OFFLINE = 0x4e45534c,		/* "LSEN" */
 	USB4_SB_OPCODE_ENUMERATE_RETIMERS = 0x4d554e45,		/* "ENUM" */
 	USB4_SB_OPCODE_SET_INBOUND_SBTX = 0x5055534c,		/* "LSUP" */
+	USB4_SB_OPCODE_UNSET_INBOUND_SBTX = 0x50555355,		/* "USUP" */
 	USB4_SB_OPCODE_QUERY_LAST_RETIMER = 0x5453414c,		/* "LAST" */
 	USB4_SB_OPCODE_GET_NVM_SECTOR_SIZE = 0x53534e47,	/* "GNSS" */
 	USB4_SB_OPCODE_NVM_SET_OFFSET = 0x53504f42,		/* "BOPS" */

drivers/thunderbolt/tb.h

@@ -1242,6 +1242,7 @@ int usb4_port_sw_margin(struct tb_port *port, unsigned int lanes, bool timing,
 int usb4_port_sw_margin_errors(struct tb_port *port, u32 *errors);
 
 int usb4_port_retimer_set_inbound_sbtx(struct tb_port *port, u8 index);
+int usb4_port_retimer_unset_inbound_sbtx(struct tb_port *port, u8 index);
 int usb4_port_retimer_read(struct tb_port *port, u8 index, u8 reg, void *buf,
 			   u8 size);
 int usb4_port_retimer_write(struct tb_port *port, u8 index, u8 reg,

drivers/thunderbolt/usb4.c

@@ -1578,6 +1578,20 @@ int usb4_port_retimer_set_inbound_sbtx(struct tb_port *port, u8 index)
 				    500);
 }
 
+/**
+ * usb4_port_retimer_unset_inbound_sbtx() - Disable sideband channel transactions
+ * @port: USB4 port
+ * @index: Retimer index
+ *
+ * Disables sideband channel transations on SBTX. The reverse of
+ * usb4_port_retimer_set_inbound_sbtx().
+ */
+int usb4_port_retimer_unset_inbound_sbtx(struct tb_port *port, u8 index)
+{
+	return usb4_port_retimer_op(port, index,
+				    USB4_SB_OPCODE_UNSET_INBOUND_SBTX, 500);
+}
+
 /**
  * usb4_port_retimer_read() - Read from retimer sideband registers
  * @port: USB4 port