[PATCH v2 2/2] usb: dwc3: Wait for control tranfer completed when stopping gadget

[Baolin Wang]

When we change the USB function with configfs dynamically, we possibly met this
situation: one core is doing the control transfer, another core is trying to
unregister the USB gadget from userspace, we must wait for completing this
control tranfer, or it will hang the controller to set the DEVCTRLHLT flag.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
---
 drivers/usb/dwc3/core.c   |    1 +
 drivers/usb/dwc3/core.h   |    2 ++
 drivers/usb/dwc3/ep0.c    |    2 ++
 drivers/usb/dwc3/gadget.c |   21 +++++++++++++++++++++
 4 files changed, 26 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 057739d..22787b6 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -999,6 +999,7 @@ static int dwc3_probe(struct platform_device *pdev)
 		goto err0;
 
 	spin_lock_init(&dwc->lock);
+	init_completion(&dwc->ep0_completed);
 
 	if (!dev->dma_mask) {
 		dev->dma_mask = dev->parent->dma_mask;
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index b2317e7..858e661 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -745,6 +745,7 @@ struct dwc3_scratchpad_array {
  * @ep0_usb_req: dummy req used while handling STD USB requests
  * @ep0_bounce_addr: dma address of ep0_bounce
  * @scratch_addr: dma address of scratchbuf
+ * @ep0_completed: One control tranfer is completed
  * @lock: for synchronizing
  * @dev: pointer to our struct device
  * @xhci: pointer to our xHCI child
@@ -843,6 +844,7 @@ struct dwc3 {
 	dma_addr_t		ep0_bounce_addr;
 	dma_addr_t		scratch_addr;
 	struct dwc3_request	ep0_usb_req;
+	struct completion	ep0_completed;
 
 	/* device lock */
 	spinlock_t		lock;
diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 632e5a4..baf932d 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -286,6 +286,7 @@ static void dwc3_ep0_stall_and_restart(struct dwc3 *dwc)
 
 	dwc->ep0state = EP0_SETUP_PHASE;
 	dwc3_ep0_out_start(dwc);
+	complete(&dwc->ep0_completed);
 }
 
 int __dwc3_gadget_ep0_set_halt(struct usb_ep *ep, int value)
@@ -935,6 +936,7 @@ static void dwc3_ep0_complete_status(struct dwc3 *dwc,
 
 	dwc->ep0state = EP0_SETUP_PHASE;
 	dwc3_ep0_out_start(dwc);
+	complete(&dwc->ep0_completed);
 }
 
 static void dwc3_ep0_xfer_complete(struct dwc3 *dwc,
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 1a33308..c9026ce 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1441,6 +1441,15 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 	if (pm_runtime_suspended(dwc->dev))
 		return 0;
 
+	/*
+	 * Per databook, when we want to stop the gadget, if a control transfer
+	 * is still in process, complete it and get the core into setup phase.
+	 */
+	if (!is_on && dwc->ep0state != EP0_SETUP_PHASE) {
+		reinit_completion(&dwc->ep0_completed);
+		return -EBUSY;
+	}
+
 	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 	if (is_on) {
 		if (dwc->revision <= DWC3_REVISION_187A) {
@@ -1491,10 +1500,22 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 
 	is_on = !!is_on;
 
+try_again:
 	spin_lock_irqsave(&dwc->lock, flags);
 	ret = dwc3_gadget_run_stop(dwc, is_on, false);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	if (ret == -EBUSY) {
+		ret = wait_for_completion_timeout(&dwc->ep0_completed,
+						  msecs_to_jiffies(100));
+		if (ret == 0) {
+			dev_err(dwc->dev, "timeout to stop gadget.\n");
+			return -ETIMEDOUT;
+		} else {
+			goto try_again;
+		}
+	}
+
 	return ret;
 }
 
-- 
1.7.9.5