On 5 March 2018 at 19:14, Roger Quadros [off-list ref] wrote:

On 05/03/18 13:06, Felipe Balbi wrote:

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Hi,

Baolin Wang [off-list ref] writes:

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Roger Quadros [off-list ref] writes:

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Roger Quadros [off-list ref] writes:

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In the following test we get stuck by sleeping forever in _dwc3_set_mode()
after which dual-role switching doesn't work.

On dra7-evm's dual-role port,
- Load g_zero gadget driver and enumerate to host
- suspend to mem
- disconnect USB cable to host and connect otg cable with Pen drive in it.
- resume system
- we sleep indefinitely in _dwc3_set_mode due to.
  dwc3_gadget_exit()->usb_del_gadget_udc()->udc_stop()->
   dwc3_gadget_stop()->wait_event_lock_irq()

Let's clear the DWC3_EP_END_TRANSFER_PENDING flag on all endpoints
so we don't wait in dwc3_gadget_stop().

Signed-off-by: Roger Quadros <redacted>
---
 drivers/usb/dwc3/gadget.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 2bda4eb..0a360da 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c

@@ -3273,6 +3273,20 @@ int dwc3_gadget_init(struct dwc3 *dwc)

 void dwc3_gadget_exit(struct dwc3 *dwc)
 {
+  int epnum;
+  unsigned long flags;
+
+  spin_lock_irqsave(&dwc->lock, flags);
+  for (epnum = 2; epnum < DWC3_ENDPOINTS_NUM; epnum++) {
+          struct dwc3_ep  *dep = dwc->eps[epnum];
+
+          if (!dep)
+                  continue;
+
+          dep->flags &= ~DWC3_EP_END_TRANSFER_PENDING;
+  }
+  spin_unlock_irqrestore(&dwc->lock, flags);
+
   usb_del_gadget_udc(&dwc->gadget);
   dwc3_gadget_free_endpoints(dwc);

free endpoints is a better place for this. It's already going to free
the memory anyway. Might as well clear all flags to 0 there.

But it won't solve the deadlock issue. Since dwc3_gadget_free_endpoints()
is called after usb_del_gadget_udc() and the deadlock happens when

usb_del_gadget_udc()->udc_stop()->dwc3_gadget_stop()->wait_event_lock_irq()

and DWC3_EP_END_TRANSFER_PENDING flag is set.

indeed. Iterating twice over the entire endpoint list seems
wasteful. Perhaps we just shouldn't wait when removing the UDC since
that's essentially what this patch will do, right? If you clear the flag
before calling ->udc_stop(), this means the loop in dwc3_gadget_stop()
will do nothing. Might as well remove it.

This means that we will never wait for DWC3_EP_END_TRANSFER_PENDING to clear
in dwc3_gadget_stop() like we used to. This is perfectly fine, right?

It makes sense to me as dwc3_gadget_stop() calls __dwc3_gadget_stop() which
masks all interrupts and nobody will ever clear that flag if it was set.

I don't think so. It can not mask the endpoint events, please check
the events which will be masked in DEVTEN register. The reason why we
should wait for DWC3_EP_END_TRANSFER_PENDING to clear is that,
sometimes the DWC3_DEPEVT_EPCMDCMPLT event will be triggered later
than 100us, but now we may have freed the gadget irq which will cause
crash.

We could mask command complete events as soon as ->udc_stop() is called,
right? Hmm, actually, __dwc3_gadget_stop() already clears DEVTEN
completely.

But which bit in DEVTEN says Endpoint events are disabled?

When we set up the DWC3_DEPCMD_ENDTRANSFER command in
dwc3_stop_active_transfer(), we can do not set DWC3_DEPCMD_CMDIOC,
then there will no endpoint command complete interrupts I think.

cmd |= DWC3_DEPCMD_CMDIOC;

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/me goes check databook

At least on revision 2.60a of the databook, bit 10 is reserved. I wonder
if that's the start of all the problems. Anybody has access to older and
newer databook revisions so we can cross-check?

I can access v2.40 and v3.10 books.

bit 10 is reserved on both

Differences in v2.4 vs v3.10 are:

bit 8   reserved        vs      L1SUSPEN
bit 13  reserved        vs      StopOnDisconnectEn
bit 14  reserved        vs      L1WKUPEVTEN

--
cheers,
-roger

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