Re: [PATCH 02/31] staging: wfx: do not send CAB while scanning

Kari Argillander
2021-09-10T16:31:07Z

On Fri, Sep 10, 2021 at 06:04:35PM +0200, Jerome Pouiller wrote:
> From: Jérôme Pouiller <jerome.pouiller@silabs.com>
>
> During the scan requests, the Tx traffic is suspended. This lock is
> shared by all the network interfaces. So, a scan request on one
> interface will block the traffic on a second interface. This causes
> trouble when the queued traffic contains CAB (Content After DTIM Beacon)
> since this traffic cannot be delayed.
>
> It could be possible to make the lock local to each interface. But It
> would only push the problem further. The device won't be able to send
> the CAB before the end of the scan.
>
> So, this patch just ignore the DTIM indication when a scan is in
> progress. The firmware will send another indication on the next DTIM and
> this time the system will be able to send the traffic just behind the
> beacon.
>
> The only drawback of this solution is that the stations connected to
> the AP will wait for traffic after the DTIM for nothing. But since the
> case is really rare it is not a big deal.
>
> Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
> ---
> drivers/staging/wfx/sta.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/staging/wfx/sta.c b/drivers/staging/wfx/sta.c
> index a236e5bb6914..d901588237a4 100644
> --- a/drivers/staging/wfx/sta.c
> +++ b/drivers/staging/wfx/sta.c
> @@ -629,8 +629,18 @@ int wfx_set_tim(struct ieee80211_hw *hw, struct ieee80211_sta *sta, bool set)
>
> void wfx_suspend_resume_mc(struct wfx_vif *wvif, enum sta_notify_cmd notify_cmd)
> {
> + struct wfx_vif *wvif_it;
> +
> if (notify_cmd != STA_NOTIFY_AWAKE)
> return;
> +
> + // Device won't be able to honor CAB if a scan is in progress on any
> + // interface. Prefer to skip this DTIM and wait for the next one.

In one patch you drop // comments but you introduce some of your self.

> + wvif_it = NULL;
> + while ((wvif_it = wvif_iterate(wvif->wdev, wvif_it)) != NULL)
> + if (mutex_is_locked(&wvif_it->scan_lock))
> + return;
> +
> if (!wfx_tx_queues_has_cab(wvif) || wvif->after_dtim_tx_allowed)
> dev_warn(wvif->wdev->dev, "incorrect sequence (%d CAB in queue)",
> wfx_tx_queues_has_cab(wvif));
> --
> 2.33.0
>