[PATCH v3] usb: dwc3: Stop active transfers before halting the controller

[Wesley Cheng]

In the DWC3 databook, for a device initiated disconnect or bus reset, the
driver is required to send dependxfer commands for any pending transfers.
In addition, before the controller can move to the halted state, the SW
needs to acknowledge any pending events.  If the controller is not halted
properly, there is a chance the controller will continue accessing stale or
freed TRBs and buffers.

Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>

---
Changes in v3:
 - Removed DWC3_EP_ENABLED check from dwc3_gadget_stop_active_transfers()
   as dwc3_stop_active_transfer() has a check already in place.
 - Calling __dwc3_gadget_stop() which ensures that DWC3 interrupt events
   are cleared, and ep0 eps are cleared for the pullup disabled case.  Not
   required to call __dwc3_gadget_start() on pullup enable, as the
   composite driver will execute udc_start() before calling pullup().

Changes in v2:
 - Moved cleanup code to the pullup() API to differentiate between device
   disconnect and hibernation.
 - Added cleanup code to the bus reset case as well.
 - Verified the move to pullup() did not reproduce the problen using the
   same test sequence.

Verified fix by adding a check for ETIMEDOUT during the run stop call.
Shell script writing to the configfs UDC file to trigger disconnect and
connect.  Batch script to have PC execute data transfers over adb (ie adb
push)  After a few iterations, we'd run into a scenario where the
controller wasn't halted.  With the following change, no failed halts after
many iterations.
---
 drivers/usb/dwc3/ep0.c    |  2 +-
 drivers/usb/dwc3/gadget.c | 49 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 59f2e8c31bd1..456aa87e8778 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -197,7 +197,7 @@ int dwc3_gadget_ep0_queue(struct usb_ep *ep, struct usb_request *request,
 	int				ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
-	if (!dep->endpoint.desc) {
+	if (!dep->endpoint.desc || !dwc->pullups_connected) {
 		dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
 				dep->name);
 		ret = -ESHUTDOWN;
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 3ab6f118c508..73bda7eaa773 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1516,7 +1516,7 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 {
 	struct dwc3		*dwc = dep->dwc;
 
-	if (!dep->endpoint.desc) {
+	if (!dep->endpoint.desc || !dwc->pullups_connected) {
 		dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
 				dep->name);
 		return -ESHUTDOWN;
@@ -1926,6 +1926,21 @@ static int dwc3_gadget_set_selfpowered(struct usb_gadget *g,
 	return 0;
 }
 
+static void dwc3_stop_active_transfers(struct dwc3 *dwc)
+{
+	u32 epnum;
+
+	for (epnum = 2; epnum < DWC3_ENDPOINTS_NUM; epnum++) {
+		struct dwc3_ep *dep;
+
+		dep = dwc->eps[epnum];
+		if (!dep)
+			continue;
+
+		dwc3_remove_requests(dwc, dep);
+	}
+}
+
 static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 {
 	u32			reg;
@@ -1971,6 +1986,8 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 	return 0;
 }
 
+static void __dwc3_gadget_stop(struct dwc3 *dwc);
+
 static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 {
 	struct dwc3		*dwc = gadget_to_dwc(g);
@@ -1994,9 +2011,37 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 		}
 	}
 
+	/*
+	 * Synchronize and disable any further event handling while controller
+	 * is being enabled/disabled.
+	 */
+	disable_irq(dwc->irq_gadget);
 	spin_lock_irqsave(&dwc->lock, flags);
+
+	/* Controller is not halted until pending events are acknowledged */
+	if (!is_on) {
+		u32 count;
+
+		/*
+		 * The databook explicitly mentions for a device-initiated
+		 * disconnect sequence, the SW needs to ensure that it ends any
+		 * active transfers.
+		 */
+		dwc3_stop_active_transfers(dwc);
+		__dwc3_gadget_stop(dwc);
+
+		count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
+		count &= DWC3_GEVNTCOUNT_MASK;
+		if (count > 0) {
+			dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
+			dwc->ev_buf->lpos = (dwc->ev_buf->lpos + count) %
+						dwc->ev_buf->length;
+		}
+	}
+
 	ret = dwc3_gadget_run_stop(dwc, is_on, false);
 	spin_unlock_irqrestore(&dwc->lock, flags);
+	enable_irq(dwc->irq_gadget);
 
 	return ret;
 }
@@ -3100,6 +3145,8 @@ static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)
 	}
 
 	dwc3_reset_gadget(dwc);
+	/* Stop any active/pending transfers when receiving bus reset */
+	dwc3_stop_active_transfers(dwc);
 
 	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 	reg &= ~DWC3_DCTL_TSTCTRL_MASK;
-- 
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