Re: [PATCH 2/3] usb: chipidea: udc: improve dTD link logic

[Xu Yang <xu.yang_2@nxp.com>]

On Thu, Sep 12, 2024 at 12:54:53AM -0400, Frank Li wrote:
> On Thu, Sep 12, 2024 at 11:35:50AM +0800, Xu Yang wrote:
> > Currently, ATDTW semaphore is used to safety link new dTD to dQH. But this
> > code has a bug when the endpoint is already in error before polling ATDTW
> > or just met error during polling ATDTW. In that cases, ATDTW will never
> > turn to 1 and the cpu will busy loop there.
> 
> It should be bug fixes, add fixes tag and cc stable.

Okay.

> 
> >
> > When the endpoint met error, ENDPTSTAT will be cleared by HW. Therefore,
> > ENDPTSTAT should also be considered during this process. In case of
> > endpoint error, the current dTD should not be pushed to the head of dQH
> > since some dTDs may be still not executed. Therefore, the link logic is
> > also improved accordingly.
> >
> > Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
> > ---
> >  drivers/usb/chipidea/udc.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
> > index b9ccf62e0a50..0ab57b87b07b 100644
> > --- a/drivers/usb/chipidea/udc.c
> > +++ b/drivers/usb/chipidea/udc.c
> > @@ -612,10 +612,17 @@ static int _hardware_enqueue(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq)
> >  		do {
> >  			hw_write(ci, OP_USBCMD, USBCMD_ATDTW, USBCMD_ATDTW);
> >  			tmp_stat = hw_read(ci, OP_ENDPTSTAT, BIT(n));
> > -		} while (!hw_read(ci, OP_USBCMD, USBCMD_ATDTW));
> > +		} while (!hw_read(ci, OP_USBCMD, USBCMD_ATDTW) && tmp_stat);
> >  		hw_write(ci, OP_USBCMD, USBCMD_ATDTW, 0);
> >  		if (tmp_stat)
> >  			goto done;
> > +
> > +		/* In case of error, ENDPTSTAT will also turn into 0, then
> > +		 * don't push this dTD to dQH head if current dTD pointer
> > +		 * is not the last dTD in previous request.
> > +		 */
> 
> OP_ENDPTSTAT will be clear by HW when the endpoint met err. This dTD don't
> push to dQH if current dTD point is not the last one in previous request.

Okay, will replace with it.

Thanks,
Xu Yang