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

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Date:   Wed, 13 Dec 2023 06:45:22 -0800
From:   Ben Greear <greearb@...delatech.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>,
        Kalle Valo <kvalo@...nel.org>
Cc:     Mario Limonciello <mario.limonciello@....com>,
        Felix Fietkau <nbd@....name>,
        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>,
        "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

On 12/13/23 5:26 AM, Lorenzo Bianconi wrote:
>> 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.
> 
> agree, I think we do not need a new parameter for this, just use the current
> APIs.

Is there a convenient way for a user to make any of those options above stick through
reboots?

To me, the ability to set system defaults through reboots is a nice feature of
module options.

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com