Hi Thinh,


On 3/19/2021 7:01 PM, Thinh Nguyen wrote:

Wesley Cheng wrote:

quoted

On 3/19/2021 5:40 PM, Thinh Nguyen wrote:

quoted

Hi,

Wesley Cheng wrote:

quoted

The current dwc3_gadget_reset_interrupt() will stop any active
transfers, but only addresses blocking of EP queuing for while we are
coming from a disconnected scenario, i.e. after receiving the disconnect
event.  If the host decides to issue a bus reset on the device, the
connected parameter will still be set to true, allowing for EP queuing
to continue while we are disabling the functions.  To avoid this, set the
connected flag to false until the stop active transfers is complete.

Signed-off-by: Wesley Cheng <redacted>
---
 drivers/usb/dwc3/gadget.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 6e14fdc..d5ed0f69 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c

@@ -3327,6 +3327,15 @@ static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)
 	u32			reg;
 
 	/*
+	 * Ideally, dwc3_reset_gadget() would trigger the function
+	 * drivers to stop any active transfers through ep disable.
+	 * However, for functions which defer ep disable, such as mass
+	 * storage, we will need to rely on the call to stop active
+	 * transfers here, and avoid allowing of request queuing.
+	 */
+	dwc->connected = false;
+
+	/*
 	 * WORKAROUND: DWC3 revisions <1.88a have an issue which
 	 * would cause a missing Disconnect Event if there's a
 	 * pending Setup Packet in the FIFO.

This doesn't look right. Did you have rebase issue with your local
change again?

BR,
Thinh

Hi Thinh,

This was rebased on Greg's usb-linus branch, which has commit
f09ddcfcb8c5 ("usb: dwc3: gadget: Prevent EP queuing while stopping
transfers") merged.

Ah I see.

quoted

commit f09ddcfcb8c5  moved the dwc->connected = true to after we have
finished stop active transfers.  However, this change will also ensure
that the connected flag is set to false to ensure that when we call stop
active transfers, nothing can prepare TRBs.  (previous commit only
addresses the case where we get the reset interrupt when coming from a
disconnected state)

That still doesn't address this issue.

Because:
1) We're still protected by the spin_lock_irq*(), so this change doesn't
make any difference while handling an event.

Thank you for the feedback.  So it is true that we lock dwc->lock while
handling EP/device events, but what these changes are trying to address
is that during dwc3_stop_active_transfers() we will eventually call
dwc3_gadget_giveback() to call the complete() functions registered by
the function driver.  Before we call the complete() callbacks, we unlock
dwc->lock, so we are no longer protected, and if there was a pending ep
queue from a function driver, that would allow it to acquire the lock
and continue preparing the TRBs.

2) We don't enable the interrupt for END_TRANSFER command completion
when doing dwc3_stop_active_transfers(), the
DWC3_EP_END_TRANSFER_PENDING flag will not be set to prevent preparing
new requests.

Agreed.  That is the reason for adding the check to dwc->connected in
__dwc3_gadget_ep_queue()

if (!dep->endpoint.desc || !dwc->pullups_connected || !dwc->connected) {
 		dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
 				dep->name);
 		return -ESHUTDOWN;

We should do dwc->connected = true when we handle connection_done
interrupt instead. The END_TRANSFER command should complete before this.

So how this change will address the issue is:

1.  IRQ handler will acquire dwc->lock
2.  dwc3_gadget_reset_handler() sets dwc->connected = false
3.  Call to dwc3_stop_active_transfers()
	---> dwc3_gadget_giveback() releases dwc->lock
4.  If there was a pending ep queue (waiting for dwc->lock) it can
continue here
5.  __dwc3_gadget_ep_queue() exits early due to dwc->connected = false
6.  dwc3_gadget_giveback() re-acquires dwc->lock and continues

Thanks
Wesley Cheng

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