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From:   Sanath S <Sanath.S@amd.com>
To:     <mario.limonciello@amd.com>, <andreas.noever@gmail.com>,
        <michael.jamet@intel.com>, <mika.westerberg@linux.intel.com>,
        <YehezkelShB@gmail.com>, <linux-usb@vger.kernel.org>,
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CC:     Sanath S <Sanath.S@amd.com>
Subject: [Patch v2 1/2] thunderbolt: Introduce tb_switch_reset_ports(), tb_port_reset() and usb4_port_reset()
Date:   Wed, 13 Dec 2023 00:46:34 +0530
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Introduce the tb_switch_reset_ports() function that resets the
downstream ports of a given switch. This helps us reset the USB4
links created by boot firmware during the init sequence.

Introduce the tb_port_reset() helper function that resets the
given port.

Introduce the usb4_port_reset() function that performs the DPR
of a given port. This function follows the CM guide specification 7.3

Suggested-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Sanath S <Sanath.S@amd.com>
---
 drivers/thunderbolt/switch.c  | 35 +++++++++++++++++++++++++++++++
 drivers/thunderbolt/tb.h      |  2 ++
 drivers/thunderbolt/tb_regs.h |  1 +
 drivers/thunderbolt/usb4.c    | 39 +++++++++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+)

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 44e9b09de47a..ef7ed92fd48e 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -626,6 +626,19 @@ int tb_port_unlock(struct tb_port *port)
 	return 0;
 }
 
+/**
+ * tb_port_reset() - Reset downstream port
+ * @port: Port to reset
+ *
+ * Helps to reconfigure the USB4 link by resetting the downstream port.
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+static int tb_port_reset(struct tb_port *port)
+{
+	return usb4_port_reset(port);
+}
+
 static int __tb_port_enable(struct tb_port *port, bool enable)
 {
 	int ret;
@@ -1547,6 +1560,28 @@ static void tb_dump_switch(const struct tb *tb, const struct tb_switch *sw)
 	       regs->__unknown1, regs->__unknown4);
 }
 
+/**
+ * tb_switch_reset_ports() - Reset downstream ports of switch.
+ * @sw: Switch whose ports need to be reset.
+ *
+ * This is applicable only for USB4 routers.
+ * tb_switch_is_usb4() needs to be called before calling this
+ * function.
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+int tb_switch_reset_ports(struct tb_switch *sw)
+{
+	struct tb_port *port;
+	int ret = -EOPNOTSUPP;
+
+	tb_switch_for_each_port(sw, port) {
+		if (tb_port_is_null(port) && port->cap_usb4)
+			return tb_port_reset(port);
+	}
+	return ret;
+}
+
 /**
  * tb_switch_reset() - reconfigure route, enable and send TB_CFG_PKG_RESET
  * @sw: Switch to reset
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index e299e53473ae..f2687ec4ac53 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -797,6 +797,7 @@ void tb_switch_remove(struct tb_switch *sw);
 void tb_switch_suspend(struct tb_switch *sw, bool runtime);
 int tb_switch_resume(struct tb_switch *sw);
 int tb_switch_reset(struct tb_switch *sw);
+int tb_switch_reset_ports(struct tb_switch *sw);
 int tb_switch_wait_for_bit(struct tb_switch *sw, u32 offset, u32 bit,
 			   u32 value, int timeout_msec);
 void tb_sw_set_unplugged(struct tb_switch *sw);
@@ -1281,6 +1282,7 @@ struct tb_port *usb4_switch_map_usb3_down(struct tb_switch *sw,
 int usb4_switch_add_ports(struct tb_switch *sw);
 void usb4_switch_remove_ports(struct tb_switch *sw);
 
+int usb4_port_reset(struct tb_port *port);
 int usb4_port_unlock(struct tb_port *port);
 int usb4_port_hotplug_enable(struct tb_port *port);
 int usb4_port_configure(struct tb_port *port);
diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index 87e4795275fe..d49530bc0d53 100644
--- a/drivers/thunderbolt/tb_regs.h
+++ b/drivers/thunderbolt/tb_regs.h
@@ -389,6 +389,7 @@ struct tb_regs_port_header {
 #define PORT_CS_18_CSA				BIT(22)
 #define PORT_CS_18_TIP				BIT(24)
 #define PORT_CS_19				0x13
+#define PORT_CS_19_DPR				BIT(0)
 #define PORT_CS_19_PC				BIT(3)
 #define PORT_CS_19_PID				BIT(4)
 #define PORT_CS_19_WOC				BIT(16)
diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
index 4277733d0021..c8a4bf33ed1c 100644
--- a/drivers/thunderbolt/usb4.c
+++ b/drivers/thunderbolt/usb4.c
@@ -1073,6 +1073,45 @@ void usb4_switch_remove_ports(struct tb_switch *sw)
 	}
 }
 
+/**
+ * usb4_port_reset() - Reset USB4 downsteam port
+ * @port: USB4 port to reset.
+ *
+ * Helps to reconfigure USB4 link by resetting downstream port.
+ *
+ * Return: Returns 0 on success or an error code on failure.
+ */
+int usb4_port_reset(struct tb_port *port)
+{
+	u32 val = 0;
+	int ret;
+
+	ret = tb_port_read(port, &val, TB_CFG_PORT,
+			port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
+
+	val = 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;
+
+	/* Wait for 10ms after requesting downstream port reset */
+	usleep_range(10000, 15000);
+
+	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);
+
+	return ret;
+}
+
 /**
  * usb4_port_unlock() - Unlock USB4 downstream port
  * @port: USB4 port to unlock
-- 
2.34.1