linux-kernel - Re: [PATCH v2] usb: cdnsp: fix issue with ZLP

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Message-ID: <20221027072421.GA75844@nchen-desktop>
Date:   Thu, 27 Oct 2022 15:24:21 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     Pawel Laszczak <pawell@...ence.com>
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] usb: cdnsp: fix issue with ZLP - added TD_SIZE = 1

On 22-10-24 10:04:35, Pawel Laszczak wrote:
> Patch modifies the TD_SIZE in TRB before ZLP TRB.
> The TD_SIZE in TRB before ZLP TRB must be set to 1 to force
> processing ZLP TRB by controller.
> 
> cc: <stable@...r.kernel.org>
> Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
> Signed-off-by: Pawel Laszczak <pawell@...ence.com>
> 
> ---
> Changelog:
> v2:
> - returned value for last TRB must be 0
> 
>  drivers/usb/cdns3/cdnsp-ring.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/cdns3/cdnsp-ring.c b/drivers/usb/cdns3/cdnsp-ring.c
> index 04dfcaa08dc4..aa79bce89d8a 100644
> --- a/drivers/usb/cdns3/cdnsp-ring.c
> +++ b/drivers/usb/cdns3/cdnsp-ring.c
> @@ -1769,8 +1769,13 @@ static u32 cdnsp_td_remainder(struct cdnsp_device *pdev,
>  
>  	/* One TRB with a zero-length data packet. */
>  	if (!more_trbs_coming || (transferred == 0 && trb_buff_len == 0) ||
> -	    trb_buff_len == td_total_len)
> +	    trb_buff_len == td_total_len) {
> +		/* Before ZLP driver needs set TD_SIZE=1. */
> +		if (more_trbs_coming)
> +			return 1;
> +
>  		return 0;
> +	}

Does that fix the issue you want at bulk transfer, which has zero-length
packet at the last packet? It seems not align with your previous fix.
Would you mind explaining more?

>  
>  	maxp = usb_endpoint_maxp(preq->pep->endpoint.desc);
>  	total_packet_count = DIV_ROUND_UP(td_total_len, maxp);
> -- 
> 2.25.1
> 

-- 

Thanks,
Peter Chen