On Fri, Apr 09, 2021 at 11:32:19AM +1000, Bassem Fahmy wrote:
> On Thu, Apr 08, 2021 at 03:26:06PM +0200, Johannes Berg wrote:
> > On Sat, 2021-02-27 at 16:58 +1100, Bassem Dawood wrote:
> > > Trigger dynamic_ps_timer to re-evaluate power saving once a null function
> > > packet (with PM = 1) is ACKed.
> >
> > Can you please say what this fixes/why the change is needed?
> >
> > johannes
> >
>
> Sure.
>
> For drivers that declare PS_NULLFUNC_STACK, when sleeping, mac80211 would send a nullfunc (with PS bit set). It won't notify the driver yet (waiting for the NULLFUNC ACK).
>
>
> a/net/mac80211/mlme.c: void ieee80211_dynamic_ps_enable_work(struct work_struct *work)
>
> if (ieee80211_hw_check(&local->hw, PS_NULLFUNC_STACK) &&
> !(ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED)) {
> if (drv_tx_frames_pending(local)) {
> mod_timer(&local->dynamic_ps_timer, jiffies +
> msecs_to_jiffies(
> local->hw.conf.dynamic_ps_timeout));
> } else {
> ieee80211_send_nullfunc(local, sdata, true);
> /* Flush to get the tx status of nullfunc frame */
> ieee80211_flush_queues(local, sdata, false);
> }
> }
>
> if (!(ieee80211_hw_check(&local->hw, REPORTS_TX_ACK_STATUS) &&
> ieee80211_hw_check(&local->hw, PS_NULLFUNC_STACK)) ||
> (ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED)) {
> ifmgd->flags &= ~IEEE80211_STA_NULLFUNC_ACKED;
> local->hw.conf.flags |= IEEE80211_CONF_PS;
> ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
> }
>
> On reception of the ACK, mac80211 will set the IEEE80211_STA_NULLFUNC_ACKED flag, but won't re-evaluate dynamic_ps_enable_work. So drivers won't get notified to sleep (until ieee80211_dynamic_ps_enable_work is re-evaluated through any other path).
>
> a/net/mac80211/status.c:static void __ieee80211_tx_status(struct ieee80211_hw *hw,
> struct ieee80211_tx_status *status,
> int rates_idx, int retry_count)
>
> if (ieee80211_is_any_nullfunc(fc) &&
> ieee80211_has_pm(fc) &&
> ieee80211_hw_check(&local->hw, REPORTS_TX_ACK_STATUS) &&
> !(info->flags & IEEE80211_TX_CTL_INJECTED) &&
> local->ps_sdata && !(local->scanning)) {
> if (info->flags & IEEE80211_TX_STAT_ACK) {
> local->ps_sdata->u.mgd.flags |=
> IEEE80211_STA_NULLFUNC_ACKED;
> } else
> mod_timer(&local->dynamic_ps_timer, jiffies +
> msecs_to_jiffies(10));
> }
>
> This change makes sure ieee80211_dynamic_ps_enable_work is evaluated once a NULLFUNC is ACKED for a more conssitent notification of the driver.
>
> Regards,
> Bassem
Hi Johannes,
Following up on this. Is the explaination clear or you need more description?
Regareds,
Bassem
