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List:       linux-usb
Subject:    Re: [PATCH] usb: dwc3: Prevent indefinite sleep in _dwc3_set_mode during suspend/resume
From:       Roger Quadros <rogerq () ti ! com>
Date:       2018-02-28 9:59:14
Message-ID: 94cd6377-1327-2309-8d69-6ab0de2bdfd4 () ti ! com
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Felipe,

On 28/02/18 09:53, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@ti.com> writes:
> > 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 <rogerq@ti.com>
> > ---
> > 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.

-- 
cheers,
-roger

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: \
                0615521-4. Kotipaikka/Domicile: Helsinki
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