RE: [PATCH 3/6] usb: gadget: mv_udc: clear corresponding interrupt when flush fifo

[Neil Zhang]

> -----Original Message-----
> From: Peter Chen [mailto:peter.chen@xxxxxxxxxxxxx]
> Sent: 2014年2月25日 9:59
> To: Neil Zhang
> Cc: balbi@xxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH 3/6] usb: gadget: mv_udc: clear corresponding interrupt
> when flush fifo
> 
> On Mon, Feb 24, 2014 at 04:03:13PM +0800, Neil Zhang wrote:
> > The interruts are useless when this endpoint is going to be flushed.
> > Especially in the enumeration phase, let's take get device description
> > for example.
> > 1. Device doesn't ACK the status package from host in time due to irq
> > is disabled by some module.
> > 2. Host find no ACK in time, and send another request.
> 
> Why device does not send NAK at that time?
> Besides, you can try to prime status at data stage, it can also avoid the
> problem usb 2.0 8.5.3.3 "Error Handling on the Last Data Transaction"
> described.
> 
> > 3. Device gets the chance to handle the interrupt, the sequence is as
> > following.
> > 	a. Flush pending requests in ep0.
> > 	b. Queue a request in ep0 according to host's request and change
> > 	   the ep0 state to DATA_STATE_XMIT.
> > 	c. Handle the pending interrupt for the last status package. But
> > 	   actually it will check the new added request instead of the status
> > 	   package and because of wront ep0 state, device will request an
> 
> %s/wront/wrong


Thanks for the catch.
> 
> Peter
> 
> > 	   unexpected status package from host.
> > 	d. The ep0 state is going mad.
> >
> > The solution is that we need clear the pending corresponding interrupt
> > as well as flush endpoint.
> >
> > Signed-off-by: Neil Zhang <zhangwm@xxxxxxxxxxx>
> > ---
> >  drivers/usb/gadget/mv_udc_core.c |    2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/usb/gadget/mv_udc_core.c
> > b/drivers/usb/gadget/mv_udc_core.c
> > index 657ac5c..d5a9bdf 100644
> > --- a/drivers/usb/gadget/mv_udc_core.c
> > +++ b/drivers/usb/gadget/mv_udc_core.c
> > @@ -692,6 +692,8 @@ static void mv_ep_fifo_flush(struct usb_ep *_ep)
> >  		}
> >  		loops--;
> >  	} while (readl(&udc->op_regs->epstatus) & bit_pos);
> > +
> > +	writel(bit_pos, &udc->op_regs->epcomplete);
> >  }
> >
> >  /* queues (submits) an I/O request to an endpoint */
> > --
> > 1.7.9.5
> >
> > --
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> >
> >
> 

Best Regards,
Neil Zhang

> --
> 
> Best Regards,
> Peter Chen