RE: [PATCH 1/2] wifi: rtw89: phy: increase RF calibration timeouts for USB transport

[Ping-Ke Shih]

Louis Kotze <loukot@xxxxxxxxx> wrote:
> USB transport adds significant latency to H2C/C2H round-trips used
> by RF calibration. The existing timeout values were designed for PCIe
> and are too tight for USB, causing "failed to wait RF DACK",
> "failed to wait RF TSSI" and similar errors on USB adapters.
> 
> Apply a 4x timeout multiplier when the device uses USB transport.
> The multiplier is applied in rtw89_phy_rfk_report_wait() so all
> calibrations benefit without changing any call sites or PCIe
> timeout values.
> 
> The 4x multiplier was chosen based on measured data from two
> independent testers (RTL8922AU, 6GHz MLO and 2.4/5GHz):
> 
>   Calibration   PCIe timeout   Max measured (USB)   4x timeout
>   PRE_NTFY           5ms              1ms              20ms
>   DACK              58ms             72ms             232ms
>   RX_DCK           128ms            374ms             512ms
>   TSSI normal       20ms             24ms              80ms
>   TSSI scan          6ms             14ms              24ms
>   TXGAPK            54ms             18ms             216ms
>   IQK               84ms             53ms             336ms
>   DPK               34ms             30ms             136ms
> 
> Tested with RTL8922AU on 6GHz MLO (5GHz + 6GHz simultaneous):
> 25 connect/disconnect cycles with zero failures.
> 
> Signed-off-by: Louis Kotze <loukot@xxxxxxxxx>

Looks good to me. But please change comment style. 

> ---
>  drivers/net/wireless/realtek/rtw89/phy.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/wireless/realtek/rtw89/phy.c b/drivers/net/wireless/realtek/rtw89/phy.c
> index e70d0e283..4d809df8b 100644
> --- a/drivers/net/wireless/realtek/rtw89/phy.c
> +++ b/drivers/net/wireless/realtek/rtw89/phy.c
> @@ -3956,6 +3956,13 @@ int rtw89_phy_rfk_report_wait(struct rtw89_dev *rtwdev, const char *rfk_name,
>         struct rtw89_rfk_wait_info *wait = &rtwdev->rfk_wait;
>         unsigned long time_left;
> 
> +       /* USB transport adds latency to H2C/C2H round-trips, so RF
> +        * calibrations take longer than on PCIe. Apply a 4x multiplier
> +        * to avoid spurious timeouts.
> +        */

For now, we don't apply networking specific comment style. Keep first line '/*'.

> +       if (rtwdev->hci.type == RTW89_HCI_TYPE_USB)
> +               ms *= 4;
> +
>         /* Since we can't receive C2H event during SER, use a fixed delay. */
>         if (test_bit(RTW89_FLAG_SER_HANDLING, rtwdev->flags)) {
>                 fsleep(1000 * ms / 2);
> --
> 2.53.0