RE: [PATCH rtw-next 0/5] wifi: rtw88: pci: Support an older design, like RTL8821AE/RTL8812AE

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

Bitterblue Smith <rtl8821cerfe2@gmail.com> wrote:
> >>>>
> >>>>    It uses RX descriptor number 511, then number 0, then it doesn't
> >>>>    want to use number 1 for "a while". It raises IMR_RDU once or twice,
> >>>>    and only then it moves on to number 1, 2...
> >>>>
> >>>>    Usually when it raises IMR_RDU there are 510 or 511 RX descriptors
> >>>>    available (out of 512), so it has no excuse.
> >>>>
> >>>>    Once it has raised IMR_RDU the RX speed doesn't exceed 70-100 Mbps
> >>>>    anymore.
> >>>
> >>> If driver can receive packets on time, how does it raise ISR_RDU?
> >>
> >> It's a mystery for me.
> >>
> >>> Is RX interrupt triggered on time?
> >>>
> >>
> >> I'm not sure how to check this. I assume it is triggered on time because
> >> the ring was always nearly empty when it raised IMR_RDU.
> >
> > If interrupt handler can handle (ignore) "empty" RX ring , it might be harmless
> > to see raised IMR_RDU, right?
> 
> It is harmless in the sense that everything keeps working, just the RX
> speed is low.

Have you dug the cause RX speed is low? The PHY rate becomes low at that time? 
Or can air capture see any weird packets? Or did you think PCIE get stuck
somehow?