Re: [PATCH v2 2/3] usb: chipidea: udc: improve dTD link logic

[Peter Chen <peter.chen@kernel.org>]

On 24-09-20 17:40:55, 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.
> 
> 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.
> 
> Fixes: 26c696c678c4 ("USB: Chipidea: rename struct ci13xxx variables from udc to ci")
> Cc: stable@vger.kernel.org
> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

The same comment, do not cc stable tree, not sure if it will affect
others.

Peter
> 
> ---
> Changes in v2:
>  - modify comments
>  - fix kernel test robot build warning by using cpu_to_le32
>  - add fix tag and cc stable
> ---
>  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 e0092c735a75..c0b8745234c6 100644
> --- a/drivers/usb/chipidea/udc.c
> +++ b/drivers/usb/chipidea/udc.c
> @@ -752,10 +752,17 @@ 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;
> +
> +		/* 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.
> +		 */
> +		if (hwep->qh.ptr->curr != cpu_to_le32(prevlastnode->dma))
> +			goto done;
>  	}
>  
>  	/*  QH configuration */
> -- 
> 2.34.1
>