usb: dwc3: rockchip: use async_schedule for initial dwc3

The dwc3_rockchip_probe() spends lots of time to initialize
the dwc3 host and pm runtime. It significantly lengthen the
boot time.

I test on RK3399 Excavator Board, the execution time of the
dwc3_rockchip_probe() on Type-C0 is about 220ms without this
patch (Type-C0 connect to PC USB port at the same time). Most
of the time is spent on remove hcd(~16ms) and pm runtime
suspend (~180ms).

1. remove hcd (~16ms)
   When do usb_remove_hcd(), the xHCI should wait 16ms to
   enter the stopped state with the following log:

   xhci-hcd xhci-hcd.11.auto: Host not halted after 16000 microseconds

2. pm runtime suspend (~180ms)
   Race condition is observed during pm runtiem suspend.

              CPU0                            CPU1
              ----                            ----
   rockchip_chg_detect_work()           pm_runtime_suspend
   -> mutex_lock(&rport->mutex)         -> dwc3_runtime_suspend()
               ||                         -> dwc3_suspend_common()
               \/                           -> dwc3_core_exit()
      USB_CHG_STATE_UNDEFINED                 -> phy_power_off(dwc->usb2_generic_phy)
               ||                               -> rockchip_usb2phy_power_off()
               \/(100ms)                          -> wait for rport->mutex
      USB_CHG_STATE_WAIT_FOR_DCD                          .
               ||                                         .
               \/(40ms)                                   .
       USB_CHG_STATE_DCD_DONE
               ||
               \/(40ms)
     USB_CHG_STATE_PRIMARY_DONE

   -> mutex_unlock(&rport->mutex)
                                               -> mutex_lock(&rport->mutex)

This patch runs the remove hcd operation and pm runtime
suspend in an async_domain to speed up the boot time. With
this patch, the dwc3_rockchip_probe() spends only ~12ms.

Change-Id: Ic60774e5c3e7be9f718c18ade86b2d95a9134b4c
Signed-off-by: William Wu <william.wu@rock-chips.com>

drivers/usb/dwc3/dwc3-rockchip.c

@@ -15,6 +15,7 @@
  * GNU General Public License for more details.
  */
 
+#include <linux/async.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/kernel.h>
@@ -612,9 +613,8 @@ out:
 	mutex_unlock(&rockchip->lock);
 }
 
-static int dwc3_rockchip_extcon_register(struct dwc3_rockchip *rockchip)
+static int dwc3_rockchip_get_extcon_dev(struct dwc3_rockchip *rockchip)
 {
-	int			ret;
 	struct device		*dev = rockchip->dev;
 	struct extcon_dev	*edev;
 
@@ -628,24 +628,8 @@ static int dwc3_rockchip_extcon_register(struct dwc3_rockchip *rockchip)
 
 		rockchip->device_nb.notifier_call =
 				dwc3_rockchip_device_notifier;
-		ret = extcon_register_notifier(edev, EXTCON_USB,
-					       &rockchip->device_nb);
-		if (ret < 0) {
-			dev_err(dev, "failed to register notifier for USB\n");
-			return ret;
-		}
-
 		rockchip->host_nb.notifier_call =
 				dwc3_rockchip_host_notifier;
-		ret = extcon_register_notifier(edev, EXTCON_USB_HOST,
-					       &rockchip->host_nb);
-		if (ret < 0) {
-			dev_err(dev, "failed to register notifier for USB HOST\n");
-			extcon_unregister_notifier(edev, EXTCON_USB,
-						   &rockchip->device_nb);
-			return ret;
-		}
-
 		rockchip->edev = edev;
 	}
 
@@ -665,6 +649,71 @@ static void dwc3_rockchip_extcon_unregister(struct dwc3_rockchip *rockchip)
 	cancel_work_sync(&rockchip->otg_work);
 }
 
+static void dwc3_rockchip_async_probe(void *data, async_cookie_t cookie)
+{
+	struct dwc3_rockchip	*rockchip = data;
+	struct device		*dev = rockchip->dev;
+	struct dwc3		*dwc = rockchip->dwc;
+	struct usb_hcd		*hcd = dev_get_drvdata(&dwc->xhci->dev);
+	int			ret;
+
+	mutex_lock(&rockchip->lock);
+
+	if (rockchip->edev) {
+		ret = extcon_register_notifier(rockchip->edev, EXTCON_USB,
+					       &rockchip->device_nb);
+		if (ret < 0) {
+			dev_err(dev, "fail to register notifier for USB Dev\n");
+			goto err;
+		}
+
+		ret = extcon_register_notifier(rockchip->edev, EXTCON_USB_HOST,
+					       &rockchip->host_nb);
+		if (ret < 0) {
+			dev_err(dev,
+				"fail to register notifier for USB HOST\n");
+			extcon_unregister_notifier(rockchip->edev, EXTCON_USB,
+						   &rockchip->device_nb);
+			goto err;
+		}
+	}
+
+	if (rockchip->edev || rockchip->dwc->dr_mode == USB_DR_MODE_OTG) {
+		if (hcd && hcd->state != HC_STATE_HALT) {
+			usb_remove_hcd(hcd->shared_hcd);
+			usb_remove_hcd(hcd);
+		}
+
+		pm_runtime_set_autosuspend_delay(dwc->dev,
+						 DWC3_ROCKCHIP_AUTOSUSPEND_DELAY);
+		pm_runtime_allow(dwc->dev);
+		pm_runtime_suspend(dwc->dev);
+		pm_runtime_put_sync(rockchip->dev);
+
+		if ((extcon_get_cable_state_(rockchip->edev,
+					     EXTCON_USB) > 0) ||
+		    (extcon_get_cable_state_(rockchip->edev,
+					     EXTCON_USB_HOST) > 0))
+			schedule_work(&rockchip->otg_work);
+	} else {
+		/*
+		 * DWC3 work as Host only mode or Peripheral
+		 * only mode, set connected flag to true, it
+		 * can avoid to reset the DWC3 controller when
+		 * resume from PM suspend which may cause the
+		 * usb device to be reenumerated.
+		 */
+		rockchip->connected = true;
+	}
+
+	ret = sysfs_create_group(&dev->kobj, &dwc3_rockchip_attr_group);
+	if (ret)
+		dev_err(dev, "failed to create sysfs group: %d\n", ret);
+
+err:
+	mutex_unlock(&rockchip->lock);
+}
+
 static int dwc3_rockchip_probe(struct platform_device *pdev)
 {
 	struct dwc3_rockchip	*rockchip;
@@ -774,41 +823,11 @@ static int dwc3_rockchip_probe(struct platform_device *pdev)
 		}
 	}
 
-	ret = dwc3_rockchip_extcon_register(rockchip);
+	ret = dwc3_rockchip_get_extcon_dev(rockchip);
 	if (ret < 0)
 		goto err2;
 
-	if (rockchip->edev || (rockchip->dwc->dr_mode == USB_DR_MODE_OTG)) {
+	async_schedule(dwc3_rockchip_async_probe, rockchip);
-		if (hcd && hcd->state != HC_STATE_HALT) {
-			usb_remove_hcd(hcd->shared_hcd);
-			usb_remove_hcd(hcd);
-		}
-
-		pm_runtime_set_autosuspend_delay(&child_pdev->dev,
-						 DWC3_ROCKCHIP_AUTOSUSPEND_DELAY);
-		pm_runtime_allow(&child_pdev->dev);
-		pm_runtime_suspend(&child_pdev->dev);
-		pm_runtime_put_sync(dev);
-
-		if ((extcon_get_cable_state_(rockchip->edev,
-					     EXTCON_USB) > 0) ||
-		    (extcon_get_cable_state_(rockchip->edev,
-					     EXTCON_USB_HOST) > 0))
-			schedule_work(&rockchip->otg_work);
-	} else {
-		/*
-		 * DWC3 work as Host only mode or Peripheral
-		 * only mode, set connected flag to true, it
-		 * can avoid to reset the DWC3 controller when
-		 * resume from PM suspend which may cause the
-		 * usb device to be reenumerated.
-		 */
-		 rockchip->connected = true;
-	}
-
-	ret = sysfs_create_group(&dev->kobj, &dwc3_rockchip_attr_group);
-	if (ret)
-		dev_err(dev, "failed to create sysfs group: %d\n", ret);
 
 	mutex_unlock(&rockchip->lock);