1.硬件原理图

看下面的原理图

VCC_OTG_EN 引脚，这个脚主要是用来控制给外部OTG设备提供电源控制的。如果设备作为DEVICE设备，这时候VBUS的电是由外部提供的，比如通过USB线和电脑连接，这个时候，VBUS的电压是由电脑提供的。

如果设备作为HOST设备，比如连接U盘，我们需要给U盘提供VBUS电压，就需要控制VCC_OTG_EN引脚给VBUS提供电压。

USB_OTG_ID 脚

这个脚用来判断有OTG设备插入

VBUS电压检测，这个电路看不懂有什么作用，硬件设计预期是希望如果有外部的USB设备给设备供电，就切换模式，但是实际上，不管设备作为HOST还是DEVICE，这个电压会一直存在。所以总觉得这个设计有点问题。

ID脚电压，没有插入OTG设备的时候，电压是1.79v，插入OTG设备的时候，电压是 0V。

2.软件控制

dts 部分

&usb0 {pinctrl-names = "iddig_irq_init", "drvvbus_init", "drvvbus_low", "drvvbus_high";pinctrl-0 = <&usb0_iddig>;pinctrl-1 = <&usb0_drvvbus>;pinctrl-2 = <&usb0_drvvbus_low>;pinctrl-3 = <&usb0_drvvbus_high>;usb-power-supply = <&mt6392_vusb_reg>;drvvbus_gpio = <&pio 0 2>;iddig_gpio = <&pio 41 2>;status = "okay";
};774 /* USB GPIO start */
775         usb0_drvvbus: drvvbus_init {
776                 pins_cmd_dat {
777                         pins = <MT8167_PIN_0_EINT0__FUNC_GPIO0>;
778                         output-low;
779                 };
780         };
781
782         usb0_drvvbus_high: drvvbus_high {
783                 pins_cmd_dat {
784                         pins = <MT8167_PIN_0_EINT0__FUNC_GPIO0>;
785                         slew-rate = <1>;
786                         output-high;
787                 };
788         };
789
790         usb0_drvvbus_low: drvvbus_low {
791                 pins_cmd_dat {
792                         pins = <MT8167_PIN_0_EINT0__FUNC_GPIO0>;
793                         slew-rate = <1>;
794                         output-low;
795                 };
796         };
797         usb0_iddig: iddig_irq_init {
798                 pins_cmd_dat {
799                         pins = <MT8167_PIN_41_KPROW1__FUNC_IDDIG>;
800                         slew-rate = <0>;
801                         bias-pull-up = <MTK_PUPD_SET_R1R0_01>;
802                 };
803         };
804 /* USB GPIO end */

引脚初始化部分

void mt_usb_init_drvvbus(void)
{
#if (!(defined(SWITCH_CHARGER) || defined(FPGA_PLATFORM))) && !(defined(OTG_BOOST_BY_SWITCH_CHARGER))
#ifdef CONFIG_OF
#if defined(CONFIG_MTK_LEGACY)mt_set_gpio_mode(drvvbus_pin, drvvbus_pin_mode);/*should set GPIO2 as gpio mode.*/mt_set_gpio_dir(drvvbus_pin, GPIO_DIR_OUT);mt_get_gpio_pull_enable(drvvbus_pin);mt_set_gpio_pull_select(drvvbus_pin, GPIO_PULL_UP);
#elseint ret = 0;DBG(0, "****%s:%d Init Drive VBUS!!!!!\n", __func__, __LINE__);if (drvvbus_pin < 0)return;if (IS_ERR(pinctrl))return;pinctrl_drvvbus = pinctrl_lookup_state(pinctrl, "drvvbus_init");if (IS_ERR(pinctrl_drvvbus)) {ret = PTR_ERR(pinctrl_drvvbus);dev_err(mtk_musb->controller, "Cannot find usb pinctrl drvvbus\n");}pinctrl_drvvbus_low = pinctrl_lookup_state(pinctrl, "drvvbus_low");if (IS_ERR(pinctrl_drvvbus_low)) {ret = PTR_ERR(pinctrl_drvvbus_low);dev_err(mtk_musb->controller, "Cannot find usb pinctrl drvvbus_low\n");}pinctrl_drvvbus_high = pinctrl_lookup_state(pinctrl, "drvvbus_high");if (IS_ERR(pinctrl_drvvbus_high)) {ret = PTR_ERR(pinctrl_drvvbus_high);dev_err(mtk_musb->controller, "Cannot find usb pinctrl drvvbus_high\n");}if (!IS_ERR(pinctrl_drvvbus)) {pinctrl_select_state(pinctrl, pinctrl_drvvbus);DBG(0, "****%s:%d end Init Drive VBUS KS!!!!!\n", __func__, __LINE__);}
#endif
#elsemt_set_gpio_mode(GPIO_OTG_DRVVBUS_PIN, GPIO_OTG_DRVVBUS_PIN_M_GPIO);/*should set GPIO2 as gpio mode.*/mt_set_gpio_dir(GPIO_OTG_DRVVBUS_PIN, GPIO_DIR_OUT);mt_get_gpio_pull_enable(GPIO_OTG_DRVVBUS_PIN);mt_set_gpio_pull_select(GPIO_OTG_DRVVBUS_PIN, GPIO_PULL_UP);
#endif
#endif
}

ID 引脚初始化部分

static void otg_int_init(void)
{
#if CONFIG_OF
#if defined(CONFIG_MTK_LEGACY)mt_set_gpio_mode(iddig_pin, GPIO_MODE_00);mt_set_gpio_dir(iddig_pin, GPIO_DIR_IN);mt_set_gpio_pull_enable(iddig_pin, GPIO_PULL_ENABLE);mt_set_gpio_pull_select(iddig_pin, GPIO_PULL_UP);mt_eint_set_sens(IDDIG_EINT_PIN, MT_LEVEL_SENSITIVE);mt_eint_set_hw_debounce(IDDIG_EINT_PIN, 64);mt_eint_registration(IDDIG_EINT_PIN, EINTF_TRIGGER_LOW, mt_usb_ext_iddig_int, FALSE);
#elseint ret = 0;DBG(0, "****%s:%d before Init IDDIG KS!!!!!\n", __func__, __LINE__);if (iddig_pin < 0) {DBG(0, "iddig_pin is invalid:%d\n", iddig_pin);return;}pinctrl_iddig = pinctrl_lookup_state(pinctrl, "iddig_irq_init");if (IS_ERR(pinctrl_iddig)) {ret = PTR_ERR(pinctrl_iddig);DBG(0, "Cannot find usb pinctrl iddig_irq_init\n");}if (IS_ERR(pinctrl) || IS_ERR(pinctrl_iddig)) {DBG(0, "pinctrl or pinctrl_iddig error\n");return;}pinctrl_select_state(pinctrl, pinctrl_iddig);DBG(0, "usb iddig_pin %d\n", iddig_pin);#if 0gpio_set_debounce(iddig_pin, 64000);DBG(0, "will call __gpio_to_irq\n");
#endifusb_iddig_number = __gpio_to_irq(iddig_pin);DBG(0, "usb usb_iddig_number %d\n", usb_iddig_number);ret = request_irq(usb_iddig_number, mt_usb_ext_iddig_int, IRQF_TRIGGER_LOW, "USB_IDDIG", NULL);if (ret > 0)DBG(0, "USB IDDIG IRQ LINE not available!!\n");elseDBG(0, "USB IDDIG IRQ LINE available!!\n");irq_set_irq_wake(usb_iddig_number, 1);
#endif
#elseu32 phy_id_pull = 0;phy_id_pull = __raw_readl(U2PHYDTM1);phy_id_pull |= ID_PULL_UP;__raw_writel(phy_id_pull, U2PHYDTM1);musb_writel(mtk_musb->mregs, USB_L1INTM, IDDIG_INT_STATUS | musb_readl(mtk_musb->mregs, USB_L1INTM));
#endif
}

USB 触发中断代码

/** handle all the irqs defined by the HDRC core. for now we expect:  other* irq sources (phy, dma, etc) will be handled first, musb->int_* values* will be assigned, and the irq will already have been acked.** called in irq context with spinlock held, irqs blocked*/
irqreturn_t musb_interrupt(struct musb *musb)
{irqreturn_t retval = IRQ_NONE;u8 devctl, power = 0;
#ifndef USE_SSUSB_QMUu32 reg = 0, ep_num = 0;
#endif#ifdef POWER_SAVING_MODEif (!(os_readl(U3D_SSUSB_U2_CTRL_0P) & SSUSB_U2_PORT_PDN)) {devctl = (u8) os_readl(U3D_DEVICE_CONTROL);power = (u8) os_readl(U3D_POWER_MANAGEMENT);} else {devctl = 0;power = 0;musb->int_usb = 0;}
#elsedevctl = (u8) os_readl(U3D_DEVICE_CONTROL);power = (u8) os_readl(U3D_POWER_MANAGEMENT);
#endif/* dev_dbg(musb->controller, "** IRQ %s usb%04x tx%04x rx%04x\n", */os_printk(K_DEBUG, "IRQ %s usb%04x tx%04x rx%04x\n",(devctl & USB_DEVCTL_HOSTMODE) ? "host" : "peripheral",musb->int_usb, musb->int_tx, musb->int_rx);if (unlikely(!musb->softconnect)) {os_printk(K_WARNIN, "!softconnect, IRQ %s usb%04x tx%04x rx%04x\n",(devctl & USB_DEVCTL_HOSTMODE) ? "host" : "peripheral",musb->int_usb, musb->int_tx, musb->int_rx);return IRQ_HANDLED;}/* the core can interrupt us for multiple reasons; docs have* a generic interrupt flowchart to follow*/if (musb->int_usb)retval |= musb_stage0_irq(musb, musb->int_usb, devctl, power);/* "stage 1" is handling endpoint irqs *//* handle endpoint 0 first */if (musb->int_tx & 1)retval |= musb_g_ep0_irq(musb);#ifndef USE_SSUSB_QMU/* RX on endpoints 1-15 */reg = musb->int_rx >> 1;ep_num = 1;while (reg) {if (reg & 1) {/* musb_ep_select(musb->mregs, ep_num); *//* REVISIT just retval = ep->rx_irq(...) */retval = IRQ_HANDLED;musb_g_rx(musb, ep_num);}reg >>= 1;ep_num++;}/* TX on endpoints 1-15 */reg = musb->int_tx >> 1;ep_num = 1;while (reg) {if (reg & 1) {/* musb_ep_select(musb->mregs, ep_num); *//* REVISIT just retval |= ep->tx_irq(...) */retval = IRQ_HANDLED;musb_g_tx(musb, ep_num);}reg >>= 1;ep_num++;}
#endifreturn retval;
}
EXPORT_SYMBOL_GPL(musb_interrupt);

中断函数注册，主要是在插入把拔出usb的时候产生中断

 /* attach to the IRQ */if (request_irq(musb->nIrq, musb->isr, IRQF_TRIGGER_LOW, dev_name(dev), musb)) {DBG(0, "request_irq %d failed!\n", musb->nIrq);status = -ENODEV;goto fail3;}

3.问题以及分析

我们项目遇到一个问题

插入OTG设备后，再拔掉，仍是OTG模式，没检测到OTG设备拔出

插入OTG设备和拔开OTG设备的软件日志

====插入OTG====
[1623:kworker/0:2][MUSB]musb_id_pin_work 376: work start, is_host=0
[1623:kworker/0:2][MUSB]musb_is_host 231: will mask PMIC charger detection
[1623:kworker/0:2][MUSB]musb_is_host 254: iddig_state = 0
[1623:kworker/0:2][MUSB]musb_is_host 283: usb_is_host = 1
[1623:kworker/0:2][MUSB]musb_id_pin_work 384: musb is as host, already lock
[1623:kworker/0:2][MUSB]musb_id_pin_work 424: force PHY to host mode, 0x6d=3e, 0x6c=2c
[1623:kworker/0:2][MUSB]musb_start 1290: start, is_host=1 is_active=0
[1623:kworker/0:2][MUSB]musb_id_pin_work 464: work end, is_host=1
[1623:kworker/0:2]musb-hdrc musb-hdrc: prop=1, power=1, is_host=1
[1623:kworker/0:2]musb-hdrc musb-hdrc: prop=2, power=1, is_host=1
[1623:kworker/0:2]musb-hdrc musb-hdrc: prop=3, power=1, is_host=1
[646:usb@1.1-service]musb-hdrc musb-hdrc: prop=2, power=1, is_host=1
[646:usb@1.1-service]musb-hdrc musb-hdrc: prop=3, power=1, is_host=1
[646:usb@1.1-service]musb-hdrc musb-hdrc: prop=1, power=1, is_host=1
[0:swapper/0][MUSB]musb_stage0_irq 1102: CONNECT (a_host) devctl 5d
[1623:kworker/0:2]scsi host1: usb-storage 1-1:1.0
[1829:cat][MUSB]musb_host_rx 2048: RX end 5 STALL
[2423:usb-storage][MUSB]musb_host_rx 2048: RX end 5 STALL
[0:swapper/0][MUSB]musb_host_rx 2048: RX end 5 STALL
[0:swapper/0][MUSB]musb_host_rx 2048: RX end 5 STALL
[0:swapper/0][MUSB]musb_host_rx 2048: RX end 5 STALL
[0:swapper/0][MUSB]musb_host_rx 2048: RX end 5 STALL
[658:Binder:536_5][MUSB]musb_host_rx 2048: RX end 5 STALL
[0:swapper/0][MUSB]musb_host_rx 2048: RX end 5 STALL====拔下OTG====[0:swapper/0][MUSB]musb_stage0_irq 1107: DISCONNECT (a_host) as Host, devctl 19
[0:swapper/0][MUSB]musb_root_disconnect 197: host disconnect (a_host)
[1623:kworker/0:2][MUSB]musb_id_pin_work 376: work start, is_host=1
[1623:kworker/0:2][MUSB]musb_is_host 231: will mask PMIC charger detection
[1623:kworker/0:2][MUSB]musb_is_host 254: iddig_state = 1
[1623:kworker/0:2][MUSB]musb_is_host 274: will unmask PMIC charger detection
[1623:kworker/0:2][MUSB]musb_is_host 283: usb_is_host = 0
[1623:kworker/0:2][MUSB]switch_int_to_host 334: enable iddig irq LOW @lin 334
[1623:kworker/0:2][MUSB]switch_int_to_host 340: switch_int_to_host is done
[1623:kworker/0:2][MUSB]musb_id_pin_work 464: work end, is_host=0
[1623:kworker/0:2]musb-hdrc musb-hdrc: prop=1, power=0, is_host=0
[1623:kworker/0:2]musb-hdrc musb-hdrc: prop=2, power=0, is_host=0
[1623:kworker/0:2]musb-hdrc musb-hdrc: prop=3, power=0, is_host=0
[646:usb@1.1-service]musb-hdrc musb-hdrc: prop=2, power=0, is_host=0
[646:usb@1.1-service]musb-hdrc musb-hdrc: prop=3, power=0, is_host=0
[646:usb@1.1-service]musb-hdrc musb-hdrc: prop=1, power=0, is_host=0

获取otg状态的函数

static bool musb_is_host(void)
{u8 devctl = 0;int iddig_state = 1;bool usb_is_host = 0;DBG(0, "will mask PMIC charger detection\n");
#ifndef FPGA_PLATFORM
#ifdef CONFIG_MTK_DUAL_INPUT_CHARGER_SUPPORT
#ifdef CONFIG_MTK_LOAD_SWITCH_FPF3040pmic_chrdet_int_en(0);
#endif
#endif
#endifmusb_platform_enable(mtk_musb);if (iddig_pin < 0) {DBG(0, "iddig_pin is invalid:%d, return non-host!\n", iddig_pin);usb_is_host = 0;return usb_is_host;}#ifdef ID_PIN_USE_EX_EINT
#if defined(CONFIG_MTK_LEGACY)iddig_state = mt_get_gpio_in(iddig_pin);
#elseiddig_state = __gpio_get_value(iddig_pin);
#endifDBG(0, "iddig_state = %d\n", iddig_state);
#elseiddig_state = 0;devctl = musb_readb(mtk_musb->mregs, MUSB_DEVCTL);DBG(0, "devctl = %x before end session\n", devctl);devctl &= ~MUSB_DEVCTL_SESSION; /* this will cause A-device change back to B-device after A-cable plug out*/musb_writeb(mtk_musb->mregs, MUSB_DEVCTL, devctl);msleep(delay_time);devctl = musb_readb(mtk_musb->mregs, MUSB_DEVCTL);DBG(0, "devctl = %x before set session\n", devctl);devctl |= MUSB_DEVCTL_SESSION;musb_writeb(mtk_musb->mregs, MUSB_DEVCTL, devctl);msleep(delay_time1);devctl = musb_readb(mtk_musb->mregs, MUSB_DEVCTL);DBG(0, "devclt = %x\n", devctl);
#endifif (devctl & MUSB_DEVCTL_BDEVICE || iddig_state) {DBG(0, "will unmask PMIC charger detection\n");
#ifndef FPGA_PLATFORMpmic_chrdet_int_en(1);
#endifusb_is_host = false;} else {usb_is_host = true;}DBG(0, "usb_is_host = %d\n", usb_is_host);return usb_is_host;
}

插拔otg 的时候，会进入这个函数里面进行判断

从日志和下面的代码可以得出一个结论，我们在插入OTG和拔下OTG的时候，软件已经正常运行了，但是拔出后，可能因为某个原因，USB处在一个错误的状态，这个状态导致再插入正常的USB就没有反应了。

static void musb_id_pin_work(struct work_struct *data)
{u8 devctl = 0;unsigned long flags;/* need prepare clock because  musb_generic_disable may call prepare clock in atomic context */mt_usb_clock_prepare(mtk_musb);spin_lock_irqsave(&mtk_musb->lock, flags);musb_generic_disable(mtk_musb);spin_unlock_irqrestore(&mtk_musb->lock, flags);down(&mtk_musb->musb_lock);DBG(0, "work start, is_host=%d\n", mtk_musb->is_host);if (mtk_musb->in_ipo_off) {DBG(0, "do nothing due to in_ipo_off\n");goto out;}wake_lock(&mtk_musb->usb_lock);mtk_musb->is_host = musb_is_host();DBG(0, "musb is as %s, already lock\n", mtk_musb->is_host?"host":"device");switch_set_state((struct switch_dev *)&otg_state, mtk_musb->is_host);if (mtk_musb->is_host) {/*setup fifo for host mode*/ep_config_from_table_for_host(mtk_musb);/* wake_lock(&mtk_musb->usb_lock); */musb_platform_set_vbus(mtk_musb, 1);/* for no VBUS sensing IP*/
#if 1/* wait VBUS ready */msleep(100);/* clear session*/devctl = musb_readb(mtk_musb->mregs, MUSB_DEVCTL);musb_writeb(mtk_musb->mregs, MUSB_DEVCTL, (devctl&(~MUSB_DEVCTL_SESSION)));/* USB MAC OFF*//* VBUSVALID=0, AVALID=0, BVALID=0, SESSEND=1, IDDIG=X */USBPHY_SET8(0x6c, 0x10);USBPHY_CLR8(0x6c, 0x2e);USBPHY_SET8(0x6d, 0x3e);DBG(0, "force PHY to idle, 0x6d=%x, 0x6c=%x\n", USBPHY_READ8(0x6d), USBPHY_READ8(0x6c));/* wait */mdelay(5);/* remove babble: NOISE_STILL_SOF:1, BABBLE_CLR_EN:0 */devctl = musb_readb(mtk_musb->mregs, MUSB_ULPI_REG_DATA);devctl = devctl | 0x80;devctl = devctl & 0xbf;musb_writeb(mtk_musb->mregs, MUSB_ULPI_REG_DATA, devctl);mdelay(5);/* restart session */devctl = musb_readb(mtk_musb->mregs, MUSB_DEVCTL);musb_writeb(mtk_musb->mregs, MUSB_DEVCTL, (devctl | MUSB_DEVCTL_SESSION));/* USB MAC ONand Host Mode*//* VBUSVALID=1, AVALID=1, BVALID=1, SESSEND=0, IDDIG=0 */USBPHY_CLR8(0x6c, 0x10);USBPHY_SET8(0x6c, 0x2c);USBPHY_SET8(0x6d, 0x3e);DBG(0, "force PHY to host mode, 0x6d=%x, 0x6c=%x\n", USBPHY_READ8(0x6d), USBPHY_READ8(0x6c));
#endifmusb_start(mtk_musb);MUSB_HST_MODE(mtk_musb);switch_int_to_device(mtk_musb);#ifdef CONFIG_PMmtk_musb->is_active = 0;DBG(0, "set active to 0 in Pm runtime issue\n");
#endif} else {DBG(0, "devctl is %x\n", musb_readb(mtk_musb->mregs, MUSB_DEVCTL));musb_writeb(mtk_musb->mregs, MUSB_DEVCTL, 0);musb_platform_set_vbus(mtk_musb, 0);/* for no VBUS sensing IP */
#if 1/* USB MAC OFF*//* VBUSVALID=0, AVALID=0, BVALID=0, SESSEND=1, IDDIG=X */USBPHY_SET8(0x6c, 0x10);USBPHY_CLR8(0x6c, 0x2e);USBPHY_SET8(0x6d, 0x3e);DBG(0, "force PHY to idle, 0x6d=%x, 0x6c=%x\n", USBPHY_READ8(0x6d), USBPHY_READ8(0x6c));
#endif#if !defined(MTK_HDMI_SUPPORT)musb_stop(mtk_musb);
#elsemt_usb_check_reconnect();/*ALPS01688604, IDDIG noise caused by MHL init*/
#endifif (wake_lock_active(&mtk_musb->usb_lock))wake_unlock(&mtk_musb->usb_lock);mtk_musb->xceiv->otg->state = OTG_STATE_B_IDLE;MUSB_DEV_MODE(mtk_musb);switch_int_to_host(mtk_musb);}
out:DBG(0, "work end, is_host=%d\n", mtk_musb->is_host);up(&mtk_musb->musb_lock);mt_usb_clock_unprepare(mtk_musb);
}

里面有一个switch_int_to_host 把设备切换成host模式，从上面的日志上看，这个函数已经执行了，但是设备没有成功切换成host模式。

所以让设备恢复正常应该不是这个函数。

void switch_int_to_host(struct musb *musb)
{
#ifdef ID_PIN_USE_EX_EINT
#if defined(CONFIG_MTK_LEGACY)mt_eint_set_polarity(IDDIG_EINT_PIN, MT_EINT_POL_NEG);mt_eint_unmask(IDDIG_EINT_PIN);
#elseirq_set_irq_type(usb_iddig_number, IRQF_TRIGGER_LOW);enable_irq(usb_iddig_number);irq_set_irq_wake(usb_iddig_number, 1);DBG(0, "enable iddig irq LOW @lin %d\n", __LINE__);
#endif
#elsemusb_writel(musb->mregs, USB_L1INTP, IDDIG_INT_STATUS);musb_writel(musb->mregs, USB_L1INTM, IDDIG_INT_STATUS|musb_readl(musb->mregs, USB_L1INTM));
#endifDBG(0, "switch_int_to_host is done\n");
}

最后我解决的方法也很简单，就是在otg拔出的时候，再connect一下usb就好了。

这个connectusb应该不是简单的connect，是让usb进入device的状态。

index b260550fb7..ba66a7444c
--- a/kernel-4.4/drivers/misc/mediatek/usb20/mt8167/usb20_host.c
+++ b/kernel-4.4/drivers/misc/mediatek/usb20/mt8167/usb20_host.c
@@ -459,6 +459,9 @@ static void musb_id_pin_work(struct work_struct *data)mtk_musb->xceiv->otg->state = OTG_STATE_B_IDLE;MUSB_DEV_MODE(mtk_musb);switch_int_to_host(mtk_musb);
+               mt_usb_connect();
+               /*weiqifa modify*/
+               printk("===weiqifa=== mt_usb_connect() \n");}out:DBG(0, "work end, is_host=%d\n", mtk_musb->is_host);

这个修改是参考了MTK的补丁，他们的做法是用一个新的GPIO口用来检测USB状态.

就是上图的那个引脚，但是可惜的是，我们引脚上接的这个脚不是GPIO功能脚，所以MTK的补丁用不上，他们的补丁也就是检测是否有USB插入，并通过OTGID脚状态，然后再适配usb的状态。

用两个GPIO一起适配的原因是为了适应系统的低功耗机制，也就是说，USB的状态只有在插入usb的时候才会设置成connect状态，如果拔出，就不是connect状态，这样可以降低功耗。刚好，我们是DC供电，不是电池供电，这个可以忽略。

关于usb状态的轮询，可以看这个函数

如果进入OTG模式后，USB会一直处在DISCONNECT状态中。

#define USB_STATE_MONITOR_DELAY 5000
static struct delayed_work usb_state_monitor_dw;
static void do_usb_state_monitor_work(struct work_struct *work)
{struct gadget_info *gi = dev_get_drvdata(android_device);struct usb_composite_dev *cdev = &gi->cdev;char *usb_state = "NO-DEV";unsigned long flags;spin_lock_irqsave(&cdev->lock, flags);if (cdev->config)usb_state = "CONFIGURED";else if (gi->connected)usb_state = "CONNECTED";elseusb_state = "DISCONNECTED";spin_unlock_irqrestore(&cdev->lock, flags);pr_info("usb_state<%s>\n", usb_state);schedule_delayed_work(&usb_state_monitor_dw, msecs_to_jiffies(USB_STATE_MONITOR_DELAY));
}

4.总结

在接手这个问题之前，我是没有搞过usb相关的，当然了，我看过很多文章和书籍，之前在rockchip平台上，我也有接触过usb相关的知识，解决实际问题还是第一次，看MTK代码的时候，大部分都是通过函数名字和变量定义猜测意图，加上硬件的一些验证。

比如

下面这个引脚的功能，参考设计和我们的设计不同，我们通过验证发现，只有这个引脚有电压，PMU就会工作走开机流程。

type-c 和传统的USB是不同的，传统的USB线为了实现OTG功能会增加一个OTG引脚，但是TPYEC上是没有这个OTG线的，看下TPYEC的引脚图。

上面有CC1、CC2引脚，是用这个来实现OTG功能的。

但是我们引脚设计上，就不会这样搞了，我们是TYPEC接口，但是实现OTG功能还是用的原来的方式，我们没有使用CC1、CC2、这几个引脚。

如下图，是使用TYPEC实现OTG的硬件原理图

普通的TYPE C充电线CC管脚通过56K电阻上拉到VBUS，而OTG线一般这是通过5.1K欧下拉接地。

推荐阅读：

专辑|Linux文章汇总

专辑|程序人生

专辑|C语言

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