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From:   Loic Poulain <loic.poulain@linaro.org>
Date:   Mon, 2 Nov 2020 20:15:46 +0100
Message-ID: <CAMZdPi88=FX7TEkJ9c=nSggvYQMghT8trUyQ5dcaRdyO1q84RQ@mail.gmail.com>
Subject: Re: [PATCH 2/3] wcn36xx: Enable firmware link monitoring
To:     "Bryan O'Donoghue" <bryan.odonoghue@linaro.org>
Cc:     Kalle Valo <kvalo@codeaurora.org>, wcn36xx@lists.infradead.org,
        linux-wireless@vger.kernel.org, Shawn Guo <shawn.guo@linaro.org>
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On Sat, 31 Oct 2020 at 14:01, Bryan O'Donoghue
<bryan.odonoghue@linaro.org> wrote:
>
> On 31/10/2020 09:57, Loic Poulain wrote:
> > On Sat, 31 Oct 2020 at 03:22, Bryan O'Donoghue
> > <bryan.odonoghue@linaro.org> wrote:
> >>
> >> This patch switches on CONNECTION_MONITOR. Once done it is up to the
> >> firmware to send keep alive and to monitor the link state.
> >>
> >> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
> >> ---
> >>   drivers/net/wireless/ath/wcn36xx/main.c | 1 +
> >>   1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/net/wireless/ath/wcn36xx/main.c b/drivers/net/wireless/ath/wcn36xx/main.c
> >> index 706728fba72d..e924cc4acde0 100644
> >> --- a/drivers/net/wireless/ath/wcn36xx/main.c
> >> +++ b/drivers/net/wireless/ath/wcn36xx/main.c
> >> @@ -1246,6 +1246,7 @@ static int wcn36xx_init_ieee80211(struct wcn36xx *wcn)
> >>          ieee80211_hw_set(wcn->hw, HAS_RATE_CONTROL);
> >>          ieee80211_hw_set(wcn->hw, SINGLE_SCAN_ON_ALL_BANDS);
> >>          ieee80211_hw_set(wcn->hw, REPORTS_TX_ACK_STATUS);
> >> +       ieee80211_hw_set(wcn->hw, CONNECTION_MONITOR);
> >
> > The problem could be that when connection monitor is enabled, mac80211
> > stop sending regular null/probe packet to the AP (as expected), but
> > also stop monitoring beacon miss:
> > https://elixir.bootlin.com/linux/v5.10-rc1/source/net/mac80211/mlme.c#L115
> >
> > That's not a big problem, but that would mean that in active mode
> > (power_save disabled, non PS), the mac80211 will not detect if the AP
> > has left immediately, and in worst case, only after 30 seconds. Note
> > that in PS mode, beacon monitoring is well done by the firmware.
> >
>
> If you pull the plug out of the AP it can take up to 30 seconds to see
> it agreed.
>
> On the flip side, the amount of NULL data packets produced drops off
> significantly once we delegate this completely to the firmware.
>
> IMO you gain more by reducing the regular runtime noise than you loose
> with the timing out of an gone away AP.

OK, fair enough!


Loic