linux-kernel - RE: [PATCH 5/6] USB: gadget: mv_udc: workaroud for missing dTD

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Date:	Tue, 25 Feb 2014 07:22:57 +0000
From:	Peter Chen <Peter.Chen@...escale.com>
To:	Neil Zhang <zhangwm@...vell.com>
CC:	"balbi@...com" <balbi@...com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 5/6] USB: gadget: mv_udc: workaroud for missing dTD



 
> > From: Peter Chen [mailto:peter.chen@...escale.com]
> > Sent: 2014年2月25日 12:19
> > To: Neil Zhang
> > Cc: balbi@...com; gregkh@...uxfoundation.org;
> > linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH 5/6] USB: gadget: mv_udc: workaroud for missing
> > dTD
> >
> > On Mon, Feb 24, 2014 at 04:03:15PM +0800, Neil Zhang wrote:
> > > There is an issue with the add dTD tripwire semaphore (ATDTW bit in
> > > USBCMD register) that can cause the controller to ignore a dTD that
> > > is added to a primed endpoint. When this happens, the software can
> > > read the tripwire bit and the status bit at '1' even though the
> > > endpoint is unprimed.
> > >
> > > After executing a dTD, the device controller endpoint state machine
> > > executes a final read of the dTD terminate bit to check if the
> > > application added a dTD to the linked list at the last moment. This
> > > read is done in the finpkt_read_latest_next_td (44) state. After the
> > > read is performed, if the terminate bit is still set, the state
> > > machine moves to unprime the endpoint. The decision to unprime the
> > > endpoint is done in the checkqh_decision (59) state, based on the
> > > value of
> > the terminate bit.
> > >
> > > Before reaching the checkqh_decision state, the state machine
> > > traverses the writeqhtd_status (57), writeqh_status (56), and
> > > release_prime_mask
> > > (42) states. As shown in the waveform, the ep_addtd_tripwire_clr
> > > signal is not set to clear the tripwire bit in these states.
> > >
> > > Signed-off-by: Neil Zhang <zhangwm@...vell.com>
> > > ---
> > >  drivers/usb/gadget/mv_udc_core.c |   20 ++++++++++++++++++++
> > >  1 file changed, 20 insertions(+)
> > >
> > > diff --git a/drivers/usb/gadget/mv_udc_core.c
> > > b/drivers/usb/gadget/mv_udc_core.c
> > > index a620cff..8df8606 100644
> > > --- a/drivers/usb/gadget/mv_udc_core.c
> > > +++ b/drivers/usb/gadget/mv_udc_core.c
> > > @@ -196,7 +196,27 @@ static int process_ep_req(struct mv_udc *udc,
> > > int
> > index,
> > >  			while (readl(&udc->op_regs->epstatus) & bit_pos)
> > >  				udelay(1);
> > >  			break;
> > > +		} else {
> > > +			if (!(readl(&udc->op_regs->epstatus) & bit_pos)) {
> > > +				/* The DMA engine thinks there is no more dTD */
> > > +				curr_dqh->next_dtd_ptr = curr_dtd->dtd_next
> > > +					& EP_QUEUE_HEAD_NEXT_POINTER_MASK;
> > > +
> > > +				/* clear active and halt bit */
> > > +				curr_dqh->size_ioc_int_sts &=
> > > +						~(DTD_STATUS_ACTIVE
> > > +						| DTD_STATUS_HALTED);
> > > +
> > > +				/* Do prime again */
> > > +				wmb();
> > > +				writel(bit_pos, &udc->op_regs->epprime);
> > > +				while (readl(&udc->op_regs->epprime) & bit_pos)
> > > +					cpu_relax();
> > > +
> > > +				break;
> > > +			}
> > >  		}
> > > +
> > >  		udelay(1);
> > >  	}
> > >
> >
> > Is it a chipidea IP issue? Any errate number for this issue?
> > Does we need it for chipidea driver?
> >
> 
> Yes, I think so.
> 9000531823	B2-Medium	Adding a dTD to a Primed Endpoint May Not Get
> Recognized
> Impacted Configuration: All device mode configurations.
> 
 
Thanks for your information.

Peter

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