linux-kernel - Re: [PATCH] wifi: iwlwifi: mvm: fix power save for MLD

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Date:   Tue, 29 Aug 2023 13:21:13 -0700
From:   Sultan Alsawaf <sultan@...neltoast.com>
To:     "Greenman, Gregory" <gregory.greenman@...el.com>
Cc:     "kvalo@...nel.org" <kvalo@...nel.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "Korenblit, Miriam Rachel" <miriam.rachel.korenblit@...el.com>,
        "Berg, Johannes" <johannes.berg@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] wifi: iwlwifi: mvm: fix power save for MLD

On Tue, Aug 29, 2023 at 04:25:45PM +0000, Greenman, Gregory wrote:
> Hi,
> 
> On Mon, 2023-08-21 at 21:07 -0700, Sultan Alsawaf wrote:
> > From: Sultan Alsawaf <sultan@...neltoast.com>
> > 
> > The conversion from bss_info_changed() to vif_cfg/link_info_changed()
> > removed a call to iwl_mvm_bss_info_changed_station_common() from what
> > became the vif_cfg_changed() path. As a result, BSS_CHANGED_PS and other
> > power save changes sent via ieee80211_vif_cfg_change_notify() are ignored
> > for MLD, which breaks power save entirely. This has a noticeable impact on
> > power consumption, causing idle package power to hover at 10 W on my
> > i9-13980HX laptop with an AX210 while connected to WiFi.
> > 
> > Add the missing iwl_mvm_bss_info_changed_station_common() call to the
> > vif_cfg_changed() path to fix power save for MLD. This brings idle package
> > power down to 1 W on my laptop, a 9 W improvement.
> > 
> > Fixes: 22c588343529 ("wifi: iwlwifi: mvm: replace bss_info_changed() with vif_cfg/link_info_changed()")
> > Signed-off-by: Sultan Alsawaf <sultan@...neltoast.com>
> > ---
> >  drivers/net/wireless/intel/iwlwifi/mvm/mld-mac80211.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/mld-mac80211.c b/drivers/net/wireless/intel/iwlwifi/mvm/mld-mac80211.c
> > index 8b6c641772ee..6abc05976870 100644
> > --- a/drivers/net/wireless/intel/iwlwifi/mvm/mld-mac80211.c
> > +++ b/drivers/net/wireless/intel/iwlwifi/mvm/mld-mac80211.c
> > @@ -731,6 +731,8 @@ static void iwl_mvm_mld_vif_cfg_changed_station(struct iwl_mvm *mvm,
> >  
> >         mvmvif->associated = vif->cfg.assoc;
> >  
> > +       iwl_mvm_bss_info_changed_station_common(mvm, vif, &vif->bss_conf,
> > +                                               changes);
> >         if (!(changes & BSS_CHANGED_ASSOC))
> >                 return;
> >  
> 
> I agree that it looks like the call to iwl_mvm_bss_info_changed_station_common() is missing here, but
> I think if is is added here then the call to iwl_mvm_power_update_mac() at the end of this function
> is not needed anymore?

That call to iwl_mvm_power_update_mac() only exists in the backport driver [1]
at the moment, hence why power save is currently broken in the upstream driver.

I wasn't aware that the backport driver had that change until after I sent this,
FWIW. :)

I agree that the iwl_mvm_power_update_mac() call in the backport driver would be
redundant with this patch.

How would you like to go about this? Shall I send a v2 reformatted for the
backport driver, with an updated commit message since power save isn't broken in
the backport driver?

Or could this be staged upstream with [1] subsequently getting dropped from the
backport driver?

Thanks,
Sultan

[1] https://git.kernel.org/pub/scm/linux/kernel/git/iwlwifi/backport-iwlwifi.git/commit/?id=c3201e3d7d88bdfa0f0a94e4141c626c35724655