linux-kernel - [PATCH] usb: dwc3: Stop active transfers before halting the controller

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Message-Id: <20200819051739.22123-1-wcheng@codeaurora.org>
Date:   Tue, 18 Aug 2020 22:17:39 -0700
From:   Wesley Cheng <wcheng@...eaurora.org>
To:     balbi@...nel.org, gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        jackp@...eaurora.org, Wesley Cheng <wcheng@...eaurora.org>
Subject: [PATCH] usb: dwc3: Stop active transfers before halting the controller

In the DWC3 databook, for a device initiated disconnect, 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@...eaurora.org>

---
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 | 59 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 57 insertions(+), 4 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..1f981942d7f9 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 +1926,24 @@ 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;
+
+		if (!(dep->flags & DWC3_EP_ENABLED))
+			continue;
+
+		dwc3_remove_requests(dwc, dep);
+	}
+}
+
 static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 {
 	u32			reg;
@@ -1950,16 +1968,37 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 
 		dwc->pullups_connected = true;
 	} else {
+		dwc->pullups_connected = false;
+
+		__dwc3_gadget_ep_disable(dwc->eps[0]);
+		__dwc3_gadget_ep_disable(dwc->eps[1]);
+
+		/*
+		 * 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);
+
 		reg &= ~DWC3_DCTL_RUN_STOP;
 
 		if (dwc->has_hibernation && !suspend)
 			reg &= ~DWC3_DCTL_KEEP_CONNECT;
-
-		dwc->pullups_connected = false;
 	}
 
 	dwc3_gadget_dctl_write_safe(dwc, reg);
 
+	/* Controller is not halted until pending events are acknowledged */
+	if (!is_on) {
+		reg = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
+		reg &= DWC3_GEVNTCOUNT_MASK;
+		if (reg > 0) {
+			dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), reg);
+			dwc->ev_buf->lpos = (dwc->ev_buf->lpos + reg) %
+						dwc->ev_buf->length;
+		}
+	}
+
 	do {
 		reg = dwc3_readl(dwc->regs, DWC3_DSTS);
 		reg &= DWC3_DSTS_DEVCTRLHLT;
@@ -1994,9 +2033,15 @@ 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);
 	ret = dwc3_gadget_run_stop(dwc, is_on, false);
 	spin_unlock_irqrestore(&dwc->lock, flags);
+	enable_irq(dwc->irq_gadget);
 
 	return ret;
 }
@@ -3535,6 +3580,14 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
 	if (!count)
 		return IRQ_NONE;
 
+	/* Controller is halted; ignore new/pending events */
+	if (!dwc->pullups_connected) {
+		dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
+		dwc->ev_buf->lpos = (dwc->ev_buf->lpos + count) %
+					dwc->ev_buf->length;
+		return IRQ_HANDLED;
+	}
+
 	evt->count = count;
 	evt->flags |= DWC3_EVENT_PENDING;
 
-- 
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