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>]

> > > +
> > > +               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?
Can I say (a) case is why we should check data_txcnt? 
For cases (b)/(c), they rely on 'tx_status == RTW89_TX_DONE'.