usb: dwc2: optionally assert phy reset when waking up

On the rk3288 USB host-only port (the one that's not the OTG-enabled
port) the PHY can get into a bad state when a wakeup is asserted (not
just a wakeup from full system suspend but also a wakeup from
autosuspend).

We can get the PHY out of its bad state by asserting its "port reset",
but unfortunately that seems to assert a reset onto the USB bus so it
could confuse things if we don't actually deenumerate / reenumerate the
device.

We can also get the PHY out of its bad state by fully resetting it using
the reset from the CRU (clock reset unit), which does a more full
reset.  The CRU-based reset appears to actually cause devices on the bus
to be removed and reinserted, which fixes the problem (albeit in a hacky
way).

It's unfortunate that we need to do a full re-enumeration of devices at
wakeup time, but this is better than alternative of letting the bus get
wedged.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Yunzhi Li <lyz@rock-chips.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/core.h

@@ -859,6 +859,8 @@ struct dwc2_hregs_backup {
  * @gadget_enabled:	Peripheral mode sub-driver initialization indicator.
  * @ll_hw_enabled:	Status of low-level hardware resources.
  * @hibernated:		True if core is hibernated
+ * @reset_phy_on_wake:	Quirk saying that we should assert PHY reset on a
+ *			remote wakeup.
  * @frame_number:       Frame number read from the core. For both device
  *			and host modes. The value ranges are from 0
  *			to HFNUM_MAX_FRNUM.
@@ -972,6 +974,7 @@ struct dwc2_hregs_backup {
  * @status_buf_dma:     DMA address for status_buf
  * @start_work:         Delayed work for handling host A-cable connection
  * @reset_work:         Delayed work for handling a port reset
+ * @phy_reset_work:     Work structure for doing a PHY reset
  * @otg_port:           OTG port number
  * @frame_list:         Frame list
  * @frame_list_dma:     Frame list DMA address
@@ -1045,6 +1048,7 @@ struct dwc2_hsotg {
 	unsigned int gadget_enabled:1;
 	unsigned int ll_hw_enabled:1;
 	unsigned int hibernated:1;
+	unsigned int reset_phy_on_wake:1;
 	u16 frame_number;
 
 	struct phy *phy;
@@ -1147,6 +1151,7 @@ struct dwc2_hsotg {
 
 	struct delayed_work start_work;
 	struct delayed_work reset_work;
+	struct work_struct phy_reset_work;
 	u8 otg_port;
 	u32 *frame_list;
 	dma_addr_t frame_list_dma;
@@ -1431,6 +1436,8 @@ int dwc2_restore_host_registers(struct dwc2_hsotg *hsotg);
 int dwc2_host_enter_hibernation(struct dwc2_hsotg *hsotg);
 int dwc2_host_exit_hibernation(struct dwc2_hsotg *hsotg,
 			       int rem_wakeup, int reset);
+static inline void dwc2_host_schedule_phy_reset(struct dwc2_hsotg *hsotg)
+{ schedule_work(&hsotg->phy_reset_work); }
 #else
 static inline int dwc2_hcd_get_frame_number(struct dwc2_hsotg *hsotg)
 { return 0; }
@@ -1454,6 +1461,7 @@ static inline int dwc2_host_enter_hibernation(struct dwc2_hsotg *hsotg)
 static inline int dwc2_host_exit_hibernation(struct dwc2_hsotg *hsotg,
 					     int rem_wakeup, int reset)
 { return 0; }
+static inline void dwc2_host_schedule_phy_reset(struct dwc2_hsotg *hsotg) {}
 
 #endif
 

drivers/usb/dwc2/core_intr.c

@@ -435,6 +435,18 @@ static void dwc2_handle_wakeup_detected_intr(struct dwc2_hsotg *hsotg)
 			/* Restart the Phy Clock */
 			pcgcctl &= ~PCGCTL_STOPPCLK;
 			dwc2_writel(hsotg, pcgcctl, PCGCTL);
+
+			/*
+			 * If we've got this quirk then the PHY is stuck upon
+			 * wakeup.  Assert reset.  This will propagate out and
+			 * eventually we'll re-enumerate the device.  Not great
+			 * but the best we can do.  We can't call phy_reset()
+			 * at interrupt time but there's no hurry, so we'll
+			 * schedule it for later.
+			 */
+			if (hsotg->reset_phy_on_wake)
+				dwc2_host_schedule_phy_reset(hsotg);
+
 			mod_timer(&hsotg->wkp_timer,
 				  jiffies + msecs_to_jiffies(71));
 		} else {

drivers/usb/dwc2/hcd.c

@@ -4376,6 +4376,17 @@ static void dwc2_hcd_reset_func(struct work_struct *work)
 	spin_unlock_irqrestore(&hsotg->lock, flags);
 }
 
+static void dwc2_hcd_phy_reset_func(struct work_struct *work)
+{
+	struct dwc2_hsotg *hsotg = container_of(work, struct dwc2_hsotg,
+						phy_reset_work);
+	int ret;
+
+	ret = phy_reset(hsotg->phy);
+	if (ret)
+		dev_warn(hsotg->dev, "PHY reset failed\n");
+}
+
 /*
  * =========================================================================
  *  Linux HC Driver Functions
@@ -5152,6 +5163,8 @@ static void dwc2_hcd_free(struct dwc2_hsotg *hsotg)
 		destroy_workqueue(hsotg->wq_otg);
 	}
 
+	cancel_work_sync(&hsotg->phy_reset_work);
+
 	del_timer(&hsotg->wkp_timer);
 }
 
@@ -5293,11 +5306,10 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg)
 		hsotg->hc_ptr_array[i] = channel;
 	}
 
-	/* Initialize hsotg start work */
+	/* Initialize work */
 	INIT_DELAYED_WORK(&hsotg->start_work, dwc2_hcd_start_func);
-
-	/* Initialize port reset work */
 	INIT_DELAYED_WORK(&hsotg->reset_work, dwc2_hcd_reset_func);
+	INIT_WORK(&hsotg->phy_reset_work, dwc2_hcd_phy_reset_func);
 
 	/*
 	 * Allocate space for storing data on status transactions. Normally no

drivers/usb/dwc2/platform.c

@@ -481,6 +481,15 @@ static int dwc2_driver_probe(struct platform_device *dev)
 		hsotg->gadget_enabled = 1;
 	}
 
+	hsotg->reset_phy_on_wake =
+		of_property_read_bool(dev->dev.of_node,
+				      "snps,reset-phy-on-wake");
+	if (hsotg->reset_phy_on_wake && !hsotg->phy) {
+		dev_warn(hsotg->dev,
+			 "Quirk reset-phy-on-wake only supports generic PHYs\n");
+		hsotg->reset_phy_on_wake = false;
+	}
+
 	if (hsotg->dr_mode != USB_DR_MODE_PERIPHERAL) {
 		retval = dwc2_hcd_init(hsotg);
 		if (retval) {