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

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Message-ID: <045bf616-f69b-4253-92ce-05744d72b084@amd.com>
Date: Tue, 16 Jan 2024 22:18:14 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: James Prestwood <prestwoj@...il.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 12/14/2023 06:39, James Prestwood wrote:
> 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
> 

All,

Just wanted to update you that I looked at this issue again over the 
holidays and it's fixed by upgrading the linux-firmware for the mt7921 
that was submitted in late November.

I get the correct performance and latency without modifying power saving 
now on my Unifi access points.

Thanks,