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

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Message-ID: <BYAPR07MB538143C4835A04CB1F2CBECADD069@BYAPR07MB5381.namprd07.prod.outlook.com>
Date:   Thu, 17 Nov 2022 06:02:43 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Peter Chen <hzpeterchen@...il.com>
CC:     "peter.chen@...nel.org" <peter.chen@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...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:

Description is not added in kernel doc but is added before "if (zlp)".

I will add as last lines in kernel doc the description:

  *
  * TD containing ZLP must have TD size set to one in penultimate TRB in TD.
 */

Will this patch be correct for you then?

Pawel

>
>/*
> * 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
>>