RE: [PATCH rtw-next v2 6/7] wifi: rtw89: handle IEEE80211_TX_CTL_REQ_TX_STATUS frames for USB

[Ping-Ke Shih <pkshih@realtek.com>]

Fedor Pchelkin <pchelkin@ispras.ru> wrote:
> On Wed, 15. Oct 01:43, Ping-Ke Shih wrote:
> > > > > +
> > > > > +               if (sw_define != skb_data->tx_rpt_sn)
> > > > > +                       continue;
> > > > > +               if (tx_status != RTW89_TX_DONE &&
> > > > > +                   data_txcnt != skb_data->tx_pkt_cnt_lmt)
> > > >
> > > > As commit message of previous patch, "When there is a failed
> > > > TX status reported by the firmware, the report is ignored until the limit
> > > > is reached or success status appears."
> > > >
> > > > Do you still need to check data_txcnt for failed cases?
> > >
> > > The question also concerns
> > >
> > >   tx_req->desc_info.tx_cnt_lmt = 8;
> > >
> > > line in rtw89_tx_rpt_enable().  'tx_cnt_lmt' is written to TX descriptor
> > > and processed by firmware.  The value defines how many times the firmware
> > > will retry transmission attempts, it will not retry more times than that.
> > >
> > > 'data_txcnt' C2H field determines the retry attempt counter for the frame
> > > returned by the firmware.  If it reaches the limit, this means we got
> > > the last report from the firmware and there would be no other firmware
> > > reports for the sent frame.  So a final tx_status should be taken
> > > uncondionally in this case.
> > >
> > > E.g. if 'tx_cnt_lmt' is set to 1, the firmware will try only once,
> > > 'data_txcnt' will be 1, too.  The limit is reached and we should take
> > > tx_status immediately as is.  So there's a higher chance of getting a
> > > failed status eventually.
> > >
> > > I set it currently to 8 as the vendor driver does.  In local testing it
> > > looks more than enough.  I've seen maximum of 5 retry attempts for the
> > > same frame (usually there are no retries at all) though my network radio
> > > environment is quite noisy.
> > >
> > > I'll add the tx_cnt_lmt related info to commit message for clarity.
> > >
> >
> > Thanks for the detail.
> >
> >     1 2 3 4 5 6 7 8
> > (a) x x x x x x x x  ==> retry 8 times, but all failure. Report at 8th C2H.
> > (b) x x x o          ==> retry 3 times, and 4th done. Report at 4th C2H.
> > (c) o                ==> just done at first one. Report at first C2H.
> >
> > For every attempt, firmware reports a C2H with tx_status, right?
> 
> Yes.
> 
> > Can I say (a) case is why we should check data_txcnt?
> > For cases (b)/(c), they rely on 'tx_status == RTW89_TX_DONE'.
> 
> We should somehow determine in case (a) when those 8 attempts for the
> frame have passed and then promptly give the report with a failed status
> up to the wireless stack.  To my mind, without checking data_txcnt
> rtw89_mac_c2h_tx_rpt() can't determine the time when to do an actual
> report if every retry attempt has failed.
> 
> Otherwise skb would remain in the queue being unreported until HCI reset
> takes place, though we already had a chance to report it as failed.

Got it.

By the way, I'd list case (d) which TX done at 8th retry and can be handled
properly as well. 

    1 2 3 4 5 6 7 8
(d) x x x x x x x o  ==> retry 8 times, and finally done. Report at 8th C2H.