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

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Date:   Thu, 14 Dec 2023 04:39:19 -0800
From:   James Prestwood <prestwoj@...il.com>
To:     Mario Limonciello <mario.limonciello@....com>,
        Ben Greear <greearb@...delatech.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Kalle Valo <kvalo@...nel.org>
Cc:     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 11:27, Mario Limonciello wrote:
> On 12/13/2023 08:45, Ben Greear wrote:
>> 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
>>
>
> Some userspace has the ability to do this.  For example in Network 
> Manager:
>
> https://unix.stackexchange.com/questions/595116/wi-fi-powersaving-in-networkmanager 
>

And recently added to IWD for this very reason, there are no decent ways 
to persist between reboots (except when using NM).

https://git.kernel.org/pub/scm/network/wireless/iwd.git/commit/?id=29edb1626d88bb713db71f7b374d8f24832fd94f

Thanks,

James