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Date:   Sat, 22 Oct 2022 21:43:18 +0800
From:   Peter Chen <peter.chen@kernel.org>
To:     Pawel Laszczak <pawell@cadence.com>
Cc:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] usb: cdnsp: fix issue with ZLP - added TD_SIZE = 1
Message-ID: <20221022134318.GA51416@nchen-desktop>
References: <1666159637-161135-1-git-send-email-pawell@cadence.com>
 <20221020132010.GA29690@nchen-desktop>
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On 22-10-21 05:03:25, Pawel Laszczak wrote:
> >
> >
> >On 22-10-19 02:07:17, 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@vger.kernel.org>
> >> Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence
> >> USBSSP DRD Driver")
> >> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> >> ---
> >>  drivers/usb/cdns3/cdnsp-ring.c | 15 ++++++++-------
> >>  1 file changed, 8 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/usb/cdns3/cdnsp-ring.c
> >> b/drivers/usb/cdns3/cdnsp-ring.c index 794e413800ae..4809d0e894bb
> >> 100644
> >> --- a/drivers/usb/cdns3/cdnsp-ring.c
> >> +++ b/drivers/usb/cdns3/cdnsp-ring.c
> >> @@ -1765,18 +1765,19 @@ static u32 cdnsp_td_remainder(struct
> >cdnsp_device *pdev,
> >>  			      struct cdnsp_request *preq,
> >>  			      bool more_trbs_coming)
> >>  {
> >> -	u32 maxp, total_packet_count;
> >> -
> >> -	/* One TRB with a zero-length data packet. */
> >> -	if (!more_trbs_coming || (transferred == 0 && trb_buff_len == 0) ||
> >> -	    trb_buff_len == td_total_len)
> >> -		return 0;
> >> +	u32 maxp, total_packet_count, remainder;
> >>
> >>  	maxp = usb_endpoint_maxp(preq->pep->endpoint.desc);
> >>  	total_packet_count = DIV_ROUND_UP(td_total_len, maxp);
> >>
> >>  	/* Queuing functions don't count the current TRB into transferred. */
> >> -	return (total_packet_count - ((transferred + trb_buff_len) / maxp));
> >> +	remainder = (total_packet_count - ((transferred + trb_buff_len) /
> >> +maxp));
> >> +
> >> +	/* Before ZLP driver needs set TD_SIZE=1. */
> >> +	if (!remainder && more_trbs_coming)
> >> +		remainder = 1;
> >
> >Without ZLP, TD_SIZE = 0 for the last TRB.
> >With ZLP, TD_SIZE = 1 for current TRB, and TD_SIZE = 0 for the next TRB (the
> >last zero-length packet) right?
> 
> Yes, you have right.
> 

Pawel, With your changes, the return value is 1 for function
cdnsp_queue_ctrl_tx. Without your changes, it is 0, something wrong?

-- 

Thanks,
Peter Chen