[Patch v3 1/4] thunderbolt: Introduce usb4_port_reset() and tb_lc_reset_port()

[Sanath S]

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

Introduce tb_lc_reset_port() function that performs the DPR through
link control registers. Supports non-USB4 routers like TBT2 and TBT3.

Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Sanath S <Sanath.S@xxxxxxx>
---
 drivers/thunderbolt/lc.c      | 44 +++++++++++++++++++++++++++++++++++
 drivers/thunderbolt/tb_regs.h |  4 ++++
 drivers/thunderbolt/usb4.c    | 39 +++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+)

diff --git a/drivers/thunderbolt/lc.c b/drivers/thunderbolt/lc.c
index 633970fbe9b0..de7276909a42 100644
--- a/drivers/thunderbolt/lc.c
+++ b/drivers/thunderbolt/lc.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2019, Intel Corporation
  * Author: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
  */
+#include <linux/delay.h>
 
 #include "tb.h"
 
@@ -45,6 +46,49 @@ static int find_port_lc_cap(struct tb_port *port)
 	return sw->cap_lc + start + phys * size;
 }
 
+/**
+ * tb_lc_reset_port() - Trigger downstream port reset through LC
+ * @port: Port that is reset
+ *
+ * Triggers downstream port reset through link controller registers.
+ * Returns %0 in case of success negative errno otherwise. Only supports
+ * non-USB4 routers with link controller (that's Thunderbolt 2 and
+ * Thunderbolt 3).
+ */
+int tb_lc_reset_port(struct tb_port *port)
+{
+	struct tb_switch *sw = port->sw;
+	int cap, ret;
+	u32 mode;
+
+	if (sw->generation < 2)
+		return -EINVAL;
+
+	cap = find_port_lc_cap(port);
+	if (cap < 0)
+		return cap;
+
+	ret = tb_sw_read(sw, &mode, TB_CFG_SWITCH, cap + TB_LC_PORT_MODE, 1);
+	if (ret)
+		return ret;
+
+	mode |= TB_LC_PORT_MODE_DPR;
+
+	ret = tb_sw_write(sw, &mode, TB_CFG_SWITCH, cap + TB_LC_PORT_MODE, 1);
+	if (ret)
+		return ret;
+
+	fsleep(10000);
+
+	ret = tb_sw_read(sw, &mode, TB_CFG_SWITCH, cap + TB_LC_PORT_MODE, 1);
+	if (ret)
+		return ret;
+
+	mode &= ~TB_LC_PORT_MODE_DPR;
+
+	return tb_sw_write(sw, &mode, TB_CFG_SWITCH, cap + TB_LC_PORT_MODE, 1);
+}
+
 static int tb_lc_set_port_configured(struct tb_port *port, bool configured)
 {
 	bool upstream = tb_is_upstream_port(port);
diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index 87e4795275fe..efcae298b370 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)
@@ -584,6 +585,9 @@ struct tb_regs_hop {
 #define TB_LC_POWER				0x740
 
 /* Link controller registers */
+#define TB_LC_PORT_MODE				0x26
+#define TB_LC_PORT_MODE_DPR			BIT(0)
+
 #define TB_LC_CS_42				0x2a
 #define TB_LC_CS_42_USB_PLUGGED			BIT(31)
 
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;
-- 
2.34.1