linux-kernel - Re: [PATCH v3] usb: cdnsp: fix issue with ZLP

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Message-ID: <CAL411-qwcboX-vTn+3oOPna+tixFNEajYi_E_rgweqrC3CcXCA@mail.gmail.com>
Date:   Thu, 17 Nov 2022 09:22:09 +0800
From:   Peter Chen <hzpeterchen@...il.com>
To:     Pawel Laszczak <pawell@...ence.com>
Cc:     peter.chen@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v3] usb: cdnsp: fix issue with ZLP - added TD_SIZE = 1

On Tue, Nov 15, 2022 at 5:22 PM Pawel Laszczak <pawell@...ence.com> 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>
> ---
> v2:
> - returned value for last TRB must be 0
> v3:
> - fix issue for request->length > 64KB
>
>  drivers/usb/cdns3/cdnsp-ring.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/cdns3/cdnsp-ring.c b/drivers/usb/cdns3/cdnsp-ring.c
> index 794e413800ae..86e1141e150f 100644
> --- a/drivers/usb/cdns3/cdnsp-ring.c
> +++ b/drivers/usb/cdns3/cdnsp-ring.c
> @@ -1763,10 +1763,15 @@ static u32 cdnsp_td_remainder(struct cdnsp_device *pdev,
>                               int trb_buff_len,
>                               unsigned int td_total_len,
>                               struct cdnsp_request *preq,
> -                             bool more_trbs_coming)
> +                             bool more_trbs_coming,
> +                             bool zlp)
>  {
>         u32 maxp, total_packet_count;
>
> +       /* Before ZLP driver needs set TD_SIZE = 1. */
> +       if (zlp)
> +               return 1;
> +

Pawel, with your change, the TD_SIZE is 1 or 0, but not like the
kernel doc defined like below:

/*
 * TD size is the number of max packet sized packets remaining in the TD
 * (*not* including this TRB).
 *
 * Total TD packet count = total_packet_count =
 *     DIV_ROUND_UP(TD size in bytes / wMaxPacketSize)
 *
 * Packets transferred up to and including this TRB = packets_transferred =
 *     rounddown(total bytes transferred including this TRB / wMaxPacketSize)
 *
 * TD size = total_packet_count - packets_transferred
 *
 * It must fit in bits 21:17, so it can't be bigger than 31.
 * This is taken care of in the TRB_TD_SIZE() macro
 *
 * The last TRB in a TD must have the TD size set to zero.
 */

Peter

>         /* One TRB with a zero-length data packet. */
>         if (!more_trbs_coming || (transferred == 0 && trb_buff_len == 0) ||
>             trb_buff_len == td_total_len)
> @@ -1960,7 +1965,8 @@ int cdnsp_queue_bulk_tx(struct cdnsp_device *pdev, struct cdnsp_request *preq)
>                 /* Set the TRB length, TD size, and interrupter fields. */
>                 remainder = cdnsp_td_remainder(pdev, enqd_len, trb_buff_len,
>                                                full_len, preq,
> -                                              more_trbs_coming);
> +                                              more_trbs_coming,
> +                                              zero_len_trb);
>
>                 length_field = TRB_LEN(trb_buff_len) | TRB_TD_SIZE(remainder) |
>                         TRB_INTR_TARGET(0);
> @@ -2025,7 +2031,7 @@ int cdnsp_queue_ctrl_tx(struct cdnsp_device *pdev, struct cdnsp_request *preq)
>
>         if (preq->request.length > 0) {
>                 remainder = cdnsp_td_remainder(pdev, 0, preq->request.length,
> -                                              preq->request.length, preq, 1);
> +                                              preq->request.length, preq, 1, 0);
>
>                 length_field = TRB_LEN(preq->request.length) |
>                                 TRB_TD_SIZE(remainder) | TRB_INTR_TARGET(0);
> @@ -2225,7 +2231,7 @@ static int cdnsp_queue_isoc_tx(struct cdnsp_device *pdev,
>                 /* Set the TRB length, TD size, & interrupter fields. */
>                 remainder = cdnsp_td_remainder(pdev, running_total,
>                                                trb_buff_len, td_len, preq,
> -                                              more_trbs_coming);
> +                                              more_trbs_coming, 0);
>
>                 length_field = TRB_LEN(trb_buff_len) | TRB_INTR_TARGET(0);
>
> --
> 2.25.1
>