usb: dwc2: add a watchdog timer for a reset on the USB

When I do continuously and quickly hotplug test on RK3308 EVB
OTG interface which is configured as uac1 function, I find
that the USB Host does not see that the device is connected
occasionally. In this case, it seems that the dwc2 controller
run into soft disconnect state, although the SftDiscon bit of
DCTL register is 0. We can't find the root cause for the time
being, fortunately, the dwc2 controller can detect the session
detected interrupt, so we can workaroud this issue depend on
this interrupt.

This patch adds a watchdog timer. When the dwc2 controller
detects the session detected interrupt for device mode, start
the watchdog timer to wait for a reset on USB. If wait for
reset timeout, do soft disconnect and soft connect in watchdog
timer function, and try to generate a device connect event to
the USB Host.

Change-Id: I9bd965b75ab3903d300302cf356cc1a843ad6e64
Signed-off-by: William Wu <william.wu@rock-chips.com>

Author: wuliangfeng

drivers/usb/dwc2/core.h

@@ -747,6 +747,7 @@ struct dwc2_hregs_backup {
  * @wf_otg:             Work object for handling Connector ID Status Change
  *                      interrupt
  * @wkp_timer:          Timer object for handling Wakeup Detected interrupt
+ * @rst_complete_timer  Timer object for a reset is detected on the USB
  * @lx_state:           Lx state of connected device
  * @gregs_backup: Backup of global registers during suspend
  * @dregs_backup: Backup of device registers during suspend
@@ -887,6 +888,7 @@ struct dwc2_hsotg {
 	struct workqueue_struct *wq_otg;
 	struct work_struct wf_otg;
 	struct timer_list wkp_timer;
+	struct timer_list rst_complete_timer;
 	enum dwc2_lx_state lx_state;
 	struct dwc2_gregs_backup gr_backup;
 	struct dwc2_dregs_backup dr_backup;
@@ -999,9 +1001,11 @@ struct dwc2_hsotg {
 	enum dwc2_ep0_state ep0_state;
 	u8 test_mode;
 
+#define DWC2_WAIT_RESET_TIMEOUT	3000 /* milliseconds */
 	struct usb_gadget gadget;
 	unsigned int enabled:1;
 	unsigned int connected:1;
+	unsigned int rst_completed:1;
 	struct dwc2_hsotg_ep *eps_in[MAX_EPS_CHANNELS];
 	struct dwc2_hsotg_ep *eps_out[MAX_EPS_CHANNELS];
 	u32 g_using_dma;

drivers/usb/dwc2/core_intr.c

@@ -311,6 +311,7 @@ static void dwc2_handle_conn_id_status_change_intr(struct dwc2_hsotg *hsotg)
  */
 static void dwc2_handle_session_req_intr(struct dwc2_hsotg *hsotg)
 {
+	u32 dctl;
 	int ret;
 
 	/* Clear interrupt */
@@ -332,6 +333,13 @@ static void dwc2_handle_session_req_intr(struct dwc2_hsotg *hsotg)
 		 * established
 		 */
 		dwc2_hsotg_disconnect(hsotg);
+
+		hsotg->rst_completed = 0;
+
+		dctl = dwc2_readl(hsotg->regs + DCTL);
+		if (!(dctl & DCTL_SFTDISCON))
+			mod_timer(&hsotg->rst_complete_timer, jiffies +
+				  msecs_to_jiffies(DWC2_WAIT_RESET_TIMEOUT));
 	}
 }
 

drivers/usb/dwc2/gadget.c

@@ -2464,8 +2464,11 @@ void dwc2_hsotg_disconnect(struct dwc2_hsotg *hsotg)
 	if (!hsotg->connected)
 		return;
 
+	del_timer(&hsotg->rst_complete_timer);
+
 	hsotg->connected = 0;
 	hsotg->test_mode = 0;
+	hsotg->rst_completed = 0;
 
 	for (ep = 0; ep < hsotg->num_of_eps; ep++) {
 		if (hsotg->eps_in[ep])
@@ -2807,6 +2810,10 @@ static irqreturn_t dwc2_hsotg_irq(int irq, void *pw)
 		u32 usb_status = dwc2_readl(hsotg->regs + GOTGCTL);
 		u32 connected = hsotg->connected;
 
+		hsotg->rst_completed = 1;
+		/* Can't del_timer_sync in interrupt */
+		del_timer(&hsotg->rst_complete_timer);
+
 		dev_dbg(hsotg->dev, "%s: USBRst\n", __func__);
 		dev_dbg(hsotg->dev, "GNPTXSTS=%08x\n",
 			dwc2_readl(hsotg->regs + GNPTXSTS));
@@ -3805,6 +3812,45 @@ static int dwc2_hsotg_hw_cfg(struct dwc2_hsotg *hsotg)
 	return 0;
 }
 
+/**
+ * dwc2_wait_reset_watchdog - Watchdog timer function for a reset on the USB
+ * @param: The device state
+ *
+ * Watchdog timer function for when the dwc2 controller fails to detect
+ * a reset on USB bus. In this case, we assume the dwc2 controller is broken,
+ * the host does not see that the device is connected, and the device does
+ * not receive reset signal on the USB. So we have to do soft disconnect
+ * and soft connect, and try to generate a device connect event to the USB
+ * host.
+ */
+static void dwc2_wait_reset_watchdog(unsigned long data)
+{
+	struct dwc2_hsotg *hsotg = (struct dwc2_hsotg *)data;
+	unsigned long flags;
+	u32 dctl;
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+
+	if (!hsotg->rst_completed) {
+		dctl = dwc2_readl(hsotg->regs + DCTL);
+
+		/*
+		 * According to the dwc2 controller databook,
+		 * Table 5-55 lists the minimum duration under various
+		 * conditions for which the Soft Disconnect bit must be
+		 * set for the USB host to detect a device disconnect.
+		 * We set minimum duration to 3 microseconds.
+		 */
+		if (!(dctl & DCTL_SFTDISCON)) {
+			dwc2_hsotg_core_disconnect(hsotg);
+			udelay(3);
+			dwc2_hsotg_core_connect(hsotg);
+		}
+	}
+
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+}
+
 /**
  * dwc2_hsotg_dump - dump state of the udc
  * @param: The device state
@@ -4002,6 +4048,9 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg, int irq)
 								epnum, 0);
 	}
 
+	setup_timer(&hsotg->rst_complete_timer, dwc2_wait_reset_watchdog,
+		    (unsigned long)hsotg);
+
 	ret = usb_add_gadget_udc(dev, &hsotg->gadget);
 	if (ret) {
 		dwc2_hsotg_ep_free_request(&hsotg->eps_out[0]->ep,
@@ -4021,6 +4070,7 @@ int dwc2_hsotg_remove(struct dwc2_hsotg *hsotg)
 {
 	usb_del_gadget_udc(&hsotg->gadget);
 	dwc2_hsotg_ep_free_request(&hsotg->eps_out[0]->ep, hsotg->ctrl_req);
+	del_timer_sync(&hsotg->rst_complete_timer);
 
 	return 0;
 }