drivers/usb/mtu3/mtu3_dr.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * mtu3_dr.c - dual role switch and host glue layer
  *
  * Copyright (C) 2016 MediaTek Inc.
  *
  * Author: Chunfeng Yun <chunfeng.yun@mediatek.com>
  */

 #include <linux/debugfs.h>
 #include <linux/irq.h>
 #include <linux/kernel.h>
 #include <linux/of_device.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/seq_file.h>
 #include <linux/uaccess.h>

 #include "mtu3.h"
 #include "mtu3_dr.h"

 #define USB2_PORT 2
 #define USB3_PORT 3

 enum mtu3_vbus_id_state {
 	MTU3_ID_FLOAT = 1,
 	MTU3_ID_GROUND,
 	MTU3_VBUS_OFF,
 	MTU3_VBUS_VALID,
 };

 static void toggle_opstate(struct ssusb_mtk *ssusb)
 {
 	if (!ssusb->otg_switch.is_u3_drd) {
 		mtu3_setbits(ssusb->mac_base, U3D_DEVICE_CONTROL, DC_SESSION);
 		mtu3_setbits(ssusb->mac_base, U3D_POWER_MANAGEMENT, SOFT_CONN);
 	}
 }

 /* only port0 supports dual-role mode */
 static int ssusb_port0_switch(struct ssusb_mtk *ssusb,
 	int version, bool tohost)
 {
 	void __iomem *ibase = ssusb->ippc_base;
 	u32 value;

 	dev_dbg(ssusb->dev, "%s (switch u%d port0 to %s)\n", __func__,
 		version, tohost ? "host" : "device");

 	if (version == USB2_PORT) {
 		/* 1. power off and disable u2 port0 */
 		value = mtu3_readl(ibase, SSUSB_U2_CTRL(0));
 		value |= SSUSB_U2_PORT_PDN | SSUSB_U2_PORT_DIS;
 		mtu3_writel(ibase, SSUSB_U2_CTRL(0), value);

 		/* 2. power on, enable u2 port0 and select its mode */
 		value = mtu3_readl(ibase, SSUSB_U2_CTRL(0));
 		value &= ~(SSUSB_U2_PORT_PDN | SSUSB_U2_PORT_DIS);
 		value = tohost ? (value | SSUSB_U2_PORT_HOST_SEL) :
 			(value & (~SSUSB_U2_PORT_HOST_SEL));
 		mtu3_writel(ibase, SSUSB_U2_CTRL(0), value);
 	} else {
 		/* 1. power off and disable u3 port0 */
 		value = mtu3_readl(ibase, SSUSB_U3_CTRL(0));
 		value |= SSUSB_U3_PORT_PDN | SSUSB_U3_PORT_DIS;
 		mtu3_writel(ibase, SSUSB_U3_CTRL(0), value);

 		/* 2. power on, enable u3 port0 and select its mode */
 		value = mtu3_readl(ibase, SSUSB_U3_CTRL(0));
 		value &= ~(SSUSB_U3_PORT_PDN | SSUSB_U3_PORT_DIS);
 		value = tohost ? (value | SSUSB_U3_PORT_HOST_SEL) :
 			(value & (~SSUSB_U3_PORT_HOST_SEL));
 		mtu3_writel(ibase, SSUSB_U3_CTRL(0), value);
 	}

 	return 0;
 }

 static void switch_port_to_host(struct ssusb_mtk *ssusb)
 {
 	u32 check_clk = 0;

 	dev_dbg(ssusb->dev, "%s\n", __func__);

 	ssusb_port0_switch(ssusb, USB2_PORT, true);

 	if (ssusb->otg_switch.is_u3_drd) {
 		ssusb_port0_switch(ssusb, USB3_PORT, true);
 		check_clk = SSUSB_U3_MAC_RST_B_STS;
 	}

 	ssusb_check_clocks(ssusb, check_clk);

 	/* after all clocks are stable */
 	toggle_opstate(ssusb);
 }

 static void switch_port_to_device(struct ssusb_mtk *ssusb)
 {
 	u32 check_clk = 0;

 	dev_dbg(ssusb->dev, "%s\n", __func__);

 	ssusb_port0_switch(ssusb, USB2_PORT, false);

 	if (ssusb->otg_switch.is_u3_drd) {
 		ssusb_port0_switch(ssusb, USB3_PORT, false);
 		check_clk = SSUSB_U3_MAC_RST_B_STS;
 	}

 	ssusb_check_clocks(ssusb, check_clk);
 }

 int ssusb_set_vbus(struct otg_switch_mtk *otg_sx, int is_on)
 {
 	struct ssusb_mtk *ssusb =
 		container_of(otg_sx, struct ssusb_mtk, otg_switch);
 	struct regulator *vbus = otg_sx->vbus;
 	int ret;

 	/* vbus is optional */
 	if (!vbus)
 		return 0;

 	dev_dbg(ssusb->dev, "%s: turn %s\n", __func__, is_on ? "on" : "off");

 	if (is_on) {
 		ret = regulator_enable(vbus);
 		if (ret) {
 			dev_err(ssusb->dev, "vbus regulator enable failed\n");
 			return ret;
 		}
 	} else {
 		regulator_disable(vbus);
 	}

 	return 0;
 }

 /*
  * switch to host: -> MTU3_VBUS_OFF --> MTU3_ID_GROUND
  * switch to device: -> MTU3_ID_FLOAT --> MTU3_VBUS_VALID
  */
 static void ssusb_set_mailbox(struct otg_switch_mtk *otg_sx,
 	enum mtu3_vbus_id_state status)
 {
 	struct ssusb_mtk *ssusb =
 		container_of(otg_sx, struct ssusb_mtk, otg_switch);
 	struct mtu3 *mtu = ssusb->u3d;

 	dev_dbg(ssusb->dev, "mailbox state(%d)\n", status);

 	switch (status) {
 	case MTU3_ID_GROUND:
 		switch_port_to_host(ssusb);
 		ssusb_set_vbus(otg_sx, 1);
 		ssusb->is_host = true;
 		break;
 	case MTU3_ID_FLOAT:
 		ssusb->is_host = false;
 		ssusb_set_vbus(otg_sx, 0);
 		switch_port_to_device(ssusb);
 		break;
 	case MTU3_VBUS_OFF:
 		mtu3_stop(mtu);
 		pm_relax(ssusb->dev);
 		break;
 	case MTU3_VBUS_VALID:
 		/* avoid suspend when works as device */
 		pm_stay_awake(ssusb->dev);
 		mtu3_start(mtu);
 		break;
 	default:
 		dev_err(ssusb->dev, "invalid state\n");
 	}
 }

 static void ssusb_id_work(struct work_struct *work)
 {
 	struct otg_switch_mtk *otg_sx =
 		container_of(work, struct otg_switch_mtk, id_work);

 	if (otg_sx->id_event)
 		ssusb_set_mailbox(otg_sx, MTU3_ID_GROUND);
 	else
 		ssusb_set_mailbox(otg_sx, MTU3_ID_FLOAT);
 }

 static void ssusb_vbus_work(struct work_struct *work)
 {
 	struct otg_switch_mtk *otg_sx =
 		container_of(work, struct otg_switch_mtk, vbus_work);

 	if (otg_sx->vbus_event)
 		ssusb_set_mailbox(otg_sx, MTU3_VBUS_VALID);
 	else
 		ssusb_set_mailbox(otg_sx, MTU3_VBUS_OFF);
 }

 /*
  * @ssusb_id_notifier is called in atomic context, but @ssusb_set_mailbox
  * may sleep, so use work queue here
  */
 static int ssusb_id_notifier(struct notifier_block *nb,
 	unsigned long event, void *ptr)
 {
 	struct otg_switch_mtk *otg_sx =
 		container_of(nb, struct otg_switch_mtk, id_nb);

 	otg_sx->id_event = event;
 	schedule_work(&otg_sx->id_work);

 	return NOTIFY_DONE;
 }

 static int ssusb_vbus_notifier(struct notifier_block *nb,
 	unsigned long event, void *ptr)
 {
 	struct otg_switch_mtk *otg_sx =
 		container_of(nb, struct otg_switch_mtk, vbus_nb);

 	otg_sx->vbus_event = event;
 	schedule_work(&otg_sx->vbus_work);

 	return NOTIFY_DONE;
 }

 static int ssusb_extcon_register(struct otg_switch_mtk *otg_sx)
 {
 	struct ssusb_mtk *ssusb =
 		container_of(otg_sx, struct ssusb_mtk, otg_switch);
 	struct extcon_dev *edev = otg_sx->edev;
 	int ret;

 	/* extcon is optional */
 	if (!edev)
 		return 0;

 	otg_sx->vbus_nb.notifier_call = ssusb_vbus_notifier;
 	ret = devm_extcon_register_notifier(ssusb->dev, edev, EXTCON_USB,
 					&otg_sx->vbus_nb);
 	if (ret < 0)
 		dev_err(ssusb->dev, "failed to register notifier for USB\n");

 	otg_sx->id_nb.notifier_call = ssusb_id_notifier;
 	ret = devm_extcon_register_notifier(ssusb->dev, edev, EXTCON_USB_HOST,
 					&otg_sx->id_nb);
 	if (ret < 0)
 		dev_err(ssusb->dev, "failed to register notifier for USB-HOST\n");

 	dev_dbg(ssusb->dev, "EXTCON_USB: %d, EXTCON_USB_HOST: %d\n",
 		extcon_get_state(edev, EXTCON_USB),
 		extcon_get_state(edev, EXTCON_USB_HOST));

 	/* default as host, switch to device mode if needed */
 	if (extcon_get_state(edev, EXTCON_USB_HOST) == false)
 		ssusb_set_mailbox(otg_sx, MTU3_ID_FLOAT);
 	if (extcon_get_state(edev, EXTCON_USB) == true)
 		ssusb_set_mailbox(otg_sx, MTU3_VBUS_VALID);

 	return 0;
 }

 /*
  * We provide an interface via debugfs to switch between host and device modes
  * depending on user input.
  * This is useful in special cases, such as uses TYPE-A receptacle but also
  * wants to support dual-role mode.
  */
 static void ssusb_mode_manual_switch(struct ssusb_mtk *ssusb, int to_host)
 {
 	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

 	if (to_host) {
 		ssusb_set_force_mode(ssusb, MTU3_DR_FORCE_HOST);
 		ssusb_set_mailbox(otg_sx, MTU3_VBUS_OFF);
 		ssusb_set_mailbox(otg_sx, MTU3_ID_GROUND);
 	} else {
 		ssusb_set_force_mode(ssusb, MTU3_DR_FORCE_DEVICE);
 		ssusb_set_mailbox(otg_sx, MTU3_ID_FLOAT);
 		ssusb_set_mailbox(otg_sx, MTU3_VBUS_VALID);
 	}
 }

 static int ssusb_mode_show(struct seq_file *sf, void *unused)
 {
 	struct ssusb_mtk *ssusb = sf->private;

 	seq_printf(sf, "current mode: %s(%s drd)\n(echo device/host)\n",
 		ssusb->is_host ? "host" : "device",
 		ssusb->otg_switch.manual_drd_enabled ? "manual" : "auto");

 	return 0;
 }

 static int ssusb_mode_open(struct inode *inode, struct file *file)
 {
 	return single_open(file, ssusb_mode_show, inode->i_private);
 }

 static ssize_t ssusb_mode_write(struct file *file,
 	const char __user *ubuf, size_t count, loff_t *ppos)
 {
 	struct seq_file *sf = file->private_data;
 	struct ssusb_mtk *ssusb = sf->private;
 	char buf[16];

 	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
 		return -EFAULT;

 	if (!strncmp(buf, "host", 4) && !ssusb->is_host) {
 		ssusb_mode_manual_switch(ssusb, 1);
 	} else if (!strncmp(buf, "device", 6) && ssusb->is_host) {
 		ssusb_mode_manual_switch(ssusb, 0);
 	} else {
 		dev_err(ssusb->dev, "wrong or duplicated setting\n");
 		return -EINVAL;
 	}

 	return count;
 }

 static const struct file_operations ssusb_mode_fops = {
 	.open = ssusb_mode_open,
 	.write = ssusb_mode_write,
 	.read = seq_read,
 	.llseek = seq_lseek,
 	.release = single_release,
 };

 static int ssusb_vbus_show(struct seq_file *sf, void *unused)
 {
 	struct ssusb_mtk *ssusb = sf->private;
 	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

 	seq_printf(sf, "vbus state: %s\n(echo on/off)\n",
 		regulator_is_enabled(otg_sx->vbus) ? "on" : "off");

 	return 0;
 }

 static int ssusb_vbus_open(struct inode *inode, struct file *file)
 {
 	return single_open(file, ssusb_vbus_show, inode->i_private);
 }

 static ssize_t ssusb_vbus_write(struct file *file,
 	const char __user *ubuf, size_t count, loff_t *ppos)
 {
 	struct seq_file *sf = file->private_data;
 	struct ssusb_mtk *ssusb = sf->private;
 	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;
 	char buf[16];
 	bool enable;

 	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
 		return -EFAULT;

 	if (kstrtobool(buf, &enable)) {
 		dev_err(ssusb->dev, "wrong setting\n");
 		return -EINVAL;
 	}

 	ssusb_set_vbus(otg_sx, enable);

 	return count;
 }

 static const struct file_operations ssusb_vbus_fops = {
 	.open = ssusb_vbus_open,
 	.write = ssusb_vbus_write,
 	.read = seq_read,
 	.llseek = seq_lseek,
 	.release = single_release,
 };

 static void ssusb_debugfs_init(struct ssusb_mtk *ssusb)
 {
 	struct dentry *root;

 	root = debugfs_create_dir(dev_name(ssusb->dev), usb_debug_root);
 	ssusb->dbgfs_root = root;

 	debugfs_create_file("mode", 0644, root, ssusb, &ssusb_mode_fops);
 	debugfs_create_file("vbus", 0644, root, ssusb, &ssusb_vbus_fops);
 }

 static void ssusb_debugfs_exit(struct ssusb_mtk *ssusb)
 {
 	debugfs_remove_recursive(ssusb->dbgfs_root);
 }

 void ssusb_set_force_mode(struct ssusb_mtk *ssusb,
 			  enum mtu3_dr_force_mode mode)
 {
 	u32 value;

 	value = mtu3_readl(ssusb->ippc_base, SSUSB_U2_CTRL(0));
 	switch (mode) {
 	case MTU3_DR_FORCE_DEVICE:
 		value |= SSUSB_U2_PORT_FORCE_IDDIG | SSUSB_U2_PORT_RG_IDDIG;
 		break;
 	case MTU3_DR_FORCE_HOST:
 		value |= SSUSB_U2_PORT_FORCE_IDDIG;
 		value &= ~SSUSB_U2_PORT_RG_IDDIG;
 		break;
 	case MTU3_DR_FORCE_NONE:
 		value &= ~(SSUSB_U2_PORT_FORCE_IDDIG | SSUSB_U2_PORT_RG_IDDIG);
 		break;
 	default:
 		return;
 	}
 	mtu3_writel(ssusb->ippc_base, SSUSB_U2_CTRL(0), value);
 }

 int ssusb_otg_switch_init(struct ssusb_mtk *ssusb)
 {
 	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

 	INIT_WORK(&otg_sx->id_work, ssusb_id_work);
 	INIT_WORK(&otg_sx->vbus_work, ssusb_vbus_work);

 	if (otg_sx->manual_drd_enabled)
 		ssusb_debugfs_init(ssusb);
 	else
 		ssusb_extcon_register(otg_sx);

 	return 0;
 }

 void ssusb_otg_switch_exit(struct ssusb_mtk *ssusb)
 {
 	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

 	if (otg_sx->manual_drd_enabled)
 		ssusb_debugfs_exit(ssusb);

 	cancel_work_sync(&otg_sx->id_work);
 	cancel_work_sync(&otg_sx->vbus_work);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* mtu3_dr.c - dual role switch and host glue layer
	*
	* Copyright (C) 2016 MediaTek Inc.
	*
	* Author: Chunfeng Yun <chunfeng.yun@mediatek.com>
	*/

	#include <linux/debugfs.h>
	#include <linux/irq.h>
	#include <linux/kernel.h>
	#include <linux/of_device.h>
	#include <linux/pinctrl/consumer.h>
	#include <linux/seq_file.h>
	#include <linux/uaccess.h>

	#include "mtu3.h"
	#include "mtu3_dr.h"

	#define USB2_PORT 2
	#define USB3_PORT 3

	enum mtu3_vbus_id_state {
	MTU3_ID_FLOAT = 1,
	MTU3_ID_GROUND,
	MTU3_VBUS_OFF,
	MTU3_VBUS_VALID,
	};

	static void toggle_opstate(struct ssusb_mtk *ssusb)
	{
	if (!ssusb->otg_switch.is_u3_drd) {
	mtu3_setbits(ssusb->mac_base, U3D_DEVICE_CONTROL, DC_SESSION);
	mtu3_setbits(ssusb->mac_base, U3D_POWER_MANAGEMENT, SOFT_CONN);
	}
	}

	/* only port0 supports dual-role mode */
	static int ssusb_port0_switch(struct ssusb_mtk *ssusb,
	int version, bool tohost)
	{
	void __iomem *ibase = ssusb->ippc_base;
	u32 value;

	dev_dbg(ssusb->dev, "%s (switch u%d port0 to %s)\n", __func__,
	version, tohost ? "host" : "device");

	if (version == USB2_PORT) {
	/* 1. power off and disable u2 port0 */
	value = mtu3_readl(ibase, SSUSB_U2_CTRL(0));
	value \|= SSUSB_U2_PORT_PDN \| SSUSB_U2_PORT_DIS;
	mtu3_writel(ibase, SSUSB_U2_CTRL(0), value);

	/* 2. power on, enable u2 port0 and select its mode */
	value = mtu3_readl(ibase, SSUSB_U2_CTRL(0));
	value &= ~(SSUSB_U2_PORT_PDN \| SSUSB_U2_PORT_DIS);
	value = tohost ? (value \| SSUSB_U2_PORT_HOST_SEL) :
	(value & (~SSUSB_U2_PORT_HOST_SEL));
	mtu3_writel(ibase, SSUSB_U2_CTRL(0), value);
	} else {
	/* 1. power off and disable u3 port0 */
	value = mtu3_readl(ibase, SSUSB_U3_CTRL(0));
	value \|= SSUSB_U3_PORT_PDN \| SSUSB_U3_PORT_DIS;
	mtu3_writel(ibase, SSUSB_U3_CTRL(0), value);

	/* 2. power on, enable u3 port0 and select its mode */
	value = mtu3_readl(ibase, SSUSB_U3_CTRL(0));
	value &= ~(SSUSB_U3_PORT_PDN \| SSUSB_U3_PORT_DIS);
	value = tohost ? (value \| SSUSB_U3_PORT_HOST_SEL) :
	(value & (~SSUSB_U3_PORT_HOST_SEL));
	mtu3_writel(ibase, SSUSB_U3_CTRL(0), value);
	}

	return 0;
	}

	static void switch_port_to_host(struct ssusb_mtk *ssusb)
	{
	u32 check_clk = 0;

	dev_dbg(ssusb->dev, "%s\n", __func__);

	ssusb_port0_switch(ssusb, USB2_PORT, true);

	if (ssusb->otg_switch.is_u3_drd) {
	ssusb_port0_switch(ssusb, USB3_PORT, true);
	check_clk = SSUSB_U3_MAC_RST_B_STS;
	}

	ssusb_check_clocks(ssusb, check_clk);

	/* after all clocks are stable */
	toggle_opstate(ssusb);
	}

	static void switch_port_to_device(struct ssusb_mtk *ssusb)
	{
	u32 check_clk = 0;

	dev_dbg(ssusb->dev, "%s\n", __func__);

	ssusb_port0_switch(ssusb, USB2_PORT, false);

	if (ssusb->otg_switch.is_u3_drd) {
	ssusb_port0_switch(ssusb, USB3_PORT, false);
	check_clk = SSUSB_U3_MAC_RST_B_STS;
	}

	ssusb_check_clocks(ssusb, check_clk);
	}

	int ssusb_set_vbus(struct otg_switch_mtk *otg_sx, int is_on)
	{
	struct ssusb_mtk *ssusb =
	container_of(otg_sx, struct ssusb_mtk, otg_switch);
	struct regulator *vbus = otg_sx->vbus;
	int ret;

	/* vbus is optional */
	if (!vbus)
	return 0;

	dev_dbg(ssusb->dev, "%s: turn %s\n", __func__, is_on ? "on" : "off");

	if (is_on) {
	ret = regulator_enable(vbus);
	if (ret) {
	dev_err(ssusb->dev, "vbus regulator enable failed\n");
	return ret;
	}
	} else {
	regulator_disable(vbus);
	}

	return 0;
	}

	/*
	* switch to host: -> MTU3_VBUS_OFF --> MTU3_ID_GROUND
	* switch to device: -> MTU3_ID_FLOAT --> MTU3_VBUS_VALID
	*/
	static void ssusb_set_mailbox(struct otg_switch_mtk *otg_sx,
	enum mtu3_vbus_id_state status)
	{
	struct ssusb_mtk *ssusb =
	container_of(otg_sx, struct ssusb_mtk, otg_switch);
	struct mtu3 *mtu = ssusb->u3d;

	dev_dbg(ssusb->dev, "mailbox state(%d)\n", status);

	switch (status) {
	case MTU3_ID_GROUND:
	switch_port_to_host(ssusb);
	ssusb_set_vbus(otg_sx, 1);
	ssusb->is_host = true;
	break;
	case MTU3_ID_FLOAT:
	ssusb->is_host = false;
	ssusb_set_vbus(otg_sx, 0);
	switch_port_to_device(ssusb);
	break;
	case MTU3_VBUS_OFF:
	mtu3_stop(mtu);
	pm_relax(ssusb->dev);
	break;
	case MTU3_VBUS_VALID:
	/* avoid suspend when works as device */
	pm_stay_awake(ssusb->dev);
	mtu3_start(mtu);
	break;
	default:
	dev_err(ssusb->dev, "invalid state\n");
	}
	}

	static void ssusb_id_work(struct work_struct *work)
	{
	struct otg_switch_mtk *otg_sx =
	container_of(work, struct otg_switch_mtk, id_work);

	if (otg_sx->id_event)
	ssusb_set_mailbox(otg_sx, MTU3_ID_GROUND);
	else
	ssusb_set_mailbox(otg_sx, MTU3_ID_FLOAT);
	}

	static void ssusb_vbus_work(struct work_struct *work)
	{
	struct otg_switch_mtk *otg_sx =
	container_of(work, struct otg_switch_mtk, vbus_work);

	if (otg_sx->vbus_event)
	ssusb_set_mailbox(otg_sx, MTU3_VBUS_VALID);
	else
	ssusb_set_mailbox(otg_sx, MTU3_VBUS_OFF);
	}

	/*
	* @ssusb_id_notifier is called in atomic context, but @ssusb_set_mailbox
	* may sleep, so use work queue here
	*/
	static int ssusb_id_notifier(struct notifier_block *nb,
	unsigned long event, void *ptr)
	{
	struct otg_switch_mtk *otg_sx =
	container_of(nb, struct otg_switch_mtk, id_nb);

	otg_sx->id_event = event;
	schedule_work(&otg_sx->id_work);

	return NOTIFY_DONE;
	}

	static int ssusb_vbus_notifier(struct notifier_block *nb,
	unsigned long event, void *ptr)
	{
	struct otg_switch_mtk *otg_sx =
	container_of(nb, struct otg_switch_mtk, vbus_nb);

	otg_sx->vbus_event = event;
	schedule_work(&otg_sx->vbus_work);

	return NOTIFY_DONE;
	}

	static int ssusb_extcon_register(struct otg_switch_mtk *otg_sx)
	{
	struct ssusb_mtk *ssusb =
	container_of(otg_sx, struct ssusb_mtk, otg_switch);
	struct extcon_dev *edev = otg_sx->edev;
	int ret;

	/* extcon is optional */
	if (!edev)
	return 0;

	otg_sx->vbus_nb.notifier_call = ssusb_vbus_notifier;
	ret = devm_extcon_register_notifier(ssusb->dev, edev, EXTCON_USB,
	&otg_sx->vbus_nb);
	if (ret < 0)
	dev_err(ssusb->dev, "failed to register notifier for USB\n");

	otg_sx->id_nb.notifier_call = ssusb_id_notifier;
	ret = devm_extcon_register_notifier(ssusb->dev, edev, EXTCON_USB_HOST,
	&otg_sx->id_nb);
	if (ret < 0)
	dev_err(ssusb->dev, "failed to register notifier for USB-HOST\n");

	dev_dbg(ssusb->dev, "EXTCON_USB: %d, EXTCON_USB_HOST: %d\n",
	extcon_get_state(edev, EXTCON_USB),
	extcon_get_state(edev, EXTCON_USB_HOST));

	/* default as host, switch to device mode if needed */
	if (extcon_get_state(edev, EXTCON_USB_HOST) == false)
	ssusb_set_mailbox(otg_sx, MTU3_ID_FLOAT);
	if (extcon_get_state(edev, EXTCON_USB) == true)
	ssusb_set_mailbox(otg_sx, MTU3_VBUS_VALID);

	return 0;
	}

	/*
	* We provide an interface via debugfs to switch between host and device modes
	* depending on user input.
	* This is useful in special cases, such as uses TYPE-A receptacle but also
	* wants to support dual-role mode.
	*/
	static void ssusb_mode_manual_switch(struct ssusb_mtk *ssusb, int to_host)
	{
	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

	if (to_host) {
	ssusb_set_force_mode(ssusb, MTU3_DR_FORCE_HOST);
	ssusb_set_mailbox(otg_sx, MTU3_VBUS_OFF);
	ssusb_set_mailbox(otg_sx, MTU3_ID_GROUND);
	} else {
	ssusb_set_force_mode(ssusb, MTU3_DR_FORCE_DEVICE);
	ssusb_set_mailbox(otg_sx, MTU3_ID_FLOAT);
	ssusb_set_mailbox(otg_sx, MTU3_VBUS_VALID);
	}
	}

	static int ssusb_mode_show(struct seq_file sf, void unused)
	{
	struct ssusb_mtk *ssusb = sf->private;

	seq_printf(sf, "current mode: %s(%s drd)\n(echo device/host)\n",
	ssusb->is_host ? "host" : "device",
	ssusb->otg_switch.manual_drd_enabled ? "manual" : "auto");

	return 0;
	}

	static int ssusb_mode_open(struct inode inode, struct file file)
	{
	return single_open(file, ssusb_mode_show, inode->i_private);
	}

	static ssize_t ssusb_mode_write(struct file *file,
	const char __user ubuf, size_t count, loff_t ppos)
	{
	struct seq_file *sf = file->private_data;
	struct ssusb_mtk *ssusb = sf->private;
	char buf[16];

	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
	return -EFAULT;

	if (!strncmp(buf, "host", 4) && !ssusb->is_host) {
	ssusb_mode_manual_switch(ssusb, 1);
	} else if (!strncmp(buf, "device", 6) && ssusb->is_host) {
	ssusb_mode_manual_switch(ssusb, 0);
	} else {
	dev_err(ssusb->dev, "wrong or duplicated setting\n");
	return -EINVAL;
	}

	return count;
	}

	static const struct file_operations ssusb_mode_fops = {
	.open = ssusb_mode_open,
	.write = ssusb_mode_write,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
	};

	static int ssusb_vbus_show(struct seq_file sf, void unused)
	{
	struct ssusb_mtk *ssusb = sf->private;
	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

	seq_printf(sf, "vbus state: %s\n(echo on/off)\n",
	regulator_is_enabled(otg_sx->vbus) ? "on" : "off");

	return 0;
	}

	static int ssusb_vbus_open(struct inode inode, struct file file)
	{
	return single_open(file, ssusb_vbus_show, inode->i_private);
	}

	static ssize_t ssusb_vbus_write(struct file *file,
	const char __user ubuf, size_t count, loff_t ppos)
	{
	struct seq_file *sf = file->private_data;
	struct ssusb_mtk *ssusb = sf->private;
	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;
	char buf[16];
	bool enable;

	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
	return -EFAULT;

	if (kstrtobool(buf, &enable)) {
	dev_err(ssusb->dev, "wrong setting\n");
	return -EINVAL;
	}

	ssusb_set_vbus(otg_sx, enable);

	return count;
	}

	static const struct file_operations ssusb_vbus_fops = {
	.open = ssusb_vbus_open,
	.write = ssusb_vbus_write,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
	};

	static void ssusb_debugfs_init(struct ssusb_mtk *ssusb)
	{
	struct dentry *root;

	root = debugfs_create_dir(dev_name(ssusb->dev), usb_debug_root);
	ssusb->dbgfs_root = root;

	debugfs_create_file("mode", 0644, root, ssusb, &ssusb_mode_fops);
	debugfs_create_file("vbus", 0644, root, ssusb, &ssusb_vbus_fops);
	}

	static void ssusb_debugfs_exit(struct ssusb_mtk *ssusb)
	{
	debugfs_remove_recursive(ssusb->dbgfs_root);
	}

	void ssusb_set_force_mode(struct ssusb_mtk *ssusb,
	enum mtu3_dr_force_mode mode)
	{
	u32 value;

	value = mtu3_readl(ssusb->ippc_base, SSUSB_U2_CTRL(0));
	switch (mode) {
	case MTU3_DR_FORCE_DEVICE:
	value \|= SSUSB_U2_PORT_FORCE_IDDIG \| SSUSB_U2_PORT_RG_IDDIG;
	break;
	case MTU3_DR_FORCE_HOST:
	value \|= SSUSB_U2_PORT_FORCE_IDDIG;
	value &= ~SSUSB_U2_PORT_RG_IDDIG;
	break;
	case MTU3_DR_FORCE_NONE:
	value &= ~(SSUSB_U2_PORT_FORCE_IDDIG \| SSUSB_U2_PORT_RG_IDDIG);
	break;
	default:
	return;
	}
	mtu3_writel(ssusb->ippc_base, SSUSB_U2_CTRL(0), value);
	}

	int ssusb_otg_switch_init(struct ssusb_mtk *ssusb)
	{
	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

	INIT_WORK(&otg_sx->id_work, ssusb_id_work);
	INIT_WORK(&otg_sx->vbus_work, ssusb_vbus_work);

	if (otg_sx->manual_drd_enabled)
	ssusb_debugfs_init(ssusb);
	else
	ssusb_extcon_register(otg_sx);

	return 0;
	}

	void ssusb_otg_switch_exit(struct ssusb_mtk *ssusb)
	{
	struct otg_switch_mtk *otg_sx = &ssusb->otg_switch;

	if (otg_sx->manual_drd_enabled)
	ssusb_debugfs_exit(ssusb);

	cancel_work_sync(&otg_sx->id_work);
	cancel_work_sync(&otg_sx->vbus_work);
	}