linux-kernel - Re: [PATCH 1/2] wifi: mt76: mt7921: Disable powersaving by default

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Date:   Wed, 13 Dec 2023 14:45:55 +0200
From:   Kalle Valo <kvalo@...nel.org>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     Felix Fietkau <nbd@....name>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        "Ryder Lee" <ryder.lee@...iatek.com>,
        Shayne Chen <shayne.chen@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Deren Wu <deren.wu@...iatek.com>,
        Ming Yen Hsieh <mingyen.hsieh@...iatek.com>,
        Ben Greear <greearb@...delatech.com>,
        "open list:MEDIATEK MT76 WIRELESS LAN DRIVER" 
        <linux-wireless@...r.kernel.org>,
        "open list:ARM/Mediatek SoC support" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Sultan Alsawaf <sultan@...neltoast.com>
Subject: Re: [PATCH 1/2] wifi: mt76: mt7921: Disable powersaving by default

Mario Limonciello <mario.limonciello@....com> writes:

> Several users have reported awful latency when powersaving is enabled
> with certain access point combinations.

What APs are these exactly? In the past 802.11 Power Save Mode was
challenging due to badly behaving APs. But nowadays with so many mobile
devices in the market I would assume that APs work a lot better. It
would be best to investigate the issues in detail and try to fix them in
mt76, assuming the bugs are in mt76 driver or firmware.

> It's also reported that the powersaving feature doesn't provide an
> ample enough savings to justify being enabled by default with these
> issues.

Any numbers or how was this concluded?

> Introduce a module parameter that would control the power saving
> behavior.  Set it to default as disabled. This mirrors what some other
> WLAN drivers like iwlwifi do.

We have already several ways to control 802.11 power save mode:

* NL80211_CMD_SET_POWER_SAVE (for example used by 'iw set power_save')

* CONFIG_CFG80211_DEFAULT_PS (for kernel level default)

* WIPHY_FLAG_PS_ON_BY_DEFAULT (for the driver to control the default setting)

Adding module parameters as a fourth method sounds confusing so not
really a fan of this. And the bar is quite high for adding new module
parameters anyway.

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches