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

[Neil Zhang]

> -----Original Message-----
> From: Peter Chen [mailto:peter.chen@xxxxxxxxxxxxx]
> Sent: 2014年2月25日 12:19
> To: Neil Zhang
> Cc: balbi@xxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> 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@xxxxxxxxxxx>
> > ---
> >  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. 

> --
> 
> Best Regards,
> Peter Chen

Best Regards,
Neil Zhang

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