Received-SPF: pass (google.com: domain of linux-wireless+bounces-759-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Message-ID: <657c0ca3-244f-47ff-940a-105c0651eeac@amd.com>
Date: Wed, 13 Dec 2023 13:26:22 -0600
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 1/2] wifi: mt76: mt7921: Disable powersaving by default
Content-Language: en-US
To: Kalle Valo <kvalo@kernel.org>
Cc: Felix Fietkau <nbd@nbd.name>, Lorenzo Bianconi <lorenzo@kernel.org>,
 Ryder Lee <ryder.lee@mediatek.com>, Shayne Chen <shayne.chen@mediatek.com>,
 Sean Wang <sean.wang@mediatek.com>, Matthias Brugger
 <matthias.bgg@gmail.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>,
 Deren Wu <deren.wu@mediatek.com>, Ming Yen Hsieh
 <mingyen.hsieh@mediatek.com>, Ben Greear <greearb@candelatech.com>,
 "open list:MEDIATEK MT76 WIRELESS LAN DRIVER"
 <linux-wireless@vger.kernel.org>,
 "open list:ARM/Mediatek SoC support" <linux-kernel@vger.kernel.org>,
 "moderated list:ARM/Mediatek SoC support"
 <linux-mediatek@lists.infradead.org>, Sultan Alsawaf <sultan@kerneltoast.com>
References: <20231212090852.162787-1-mario.limonciello@amd.com>
 <874jgmnud8.fsf@kernel.org>
From: Mario Limonciello <mario.limonciello@amd.com>
In-Reply-To: <874jgmnud8.fsf@kernel.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?utf-8?B?U2VaRU5pVElzTG0weHFTTjlqUFRMSWY5OEt5eGhuQlpldHBnTGFQY0VCUWda?=
 =?utf-8?B?YlFONXIxVnRhcys5VllWVDM2UzlpVzhvT1AzeXl0ZDZqaS9HY1NyVlpiQ0pI?=
 =?utf-8?B?RmtrY2dSWitPWDV1S2RTMU9WRXRYKzh4UXFOZjZDeFFRcStnelZSd3g2SFN5?=
 =?utf-8?B?Y0Q2Z1pUakY0UjlqM2tBWHhHQ0lQWGhiTzZxdCtmUnNxeU1qaGQ5cFM1ZjNi?=
 =?utf-8?B?L3ZCaSs3VkR6SVpzUUduT0ZBQTVpY0daWlY3QUJUNlpETW0yRDlHNjNQYjhz?=
 =?utf-8?B?N2k5QkM2ZERhTlg4VXB2S0wvNEpOOTVVaGFweG02ZS8xajYwT01JMEZRSlcw?=
 =?utf-8?B?Szcyb0pUTGJkT3RRWTRuYWc5bVIrYkVhalJGb1UwQ3JpcE54TjBTR2htbWc0?=
 =?utf-8?B?WXF0dmhJTU5BMXRxYjdMVWpuM1Btd0tGRmRuRGg5VEViUGM2eDk5anloelFZ?=
 =?utf-8?B?eHdDc3VaZkRja1huRW9LNTRSTFY5WWlqZ0J0YzVhbnJrUnI5RXl6ZW1pclpD?=
 =?utf-8?B?bEk5TkROc2Z3QzY3MXpKd295KzZvd0g4UnlXQVRvVzhOcTZPY21va0pvOHhT?=
 =?utf-8?B?dm14NFk5eUVKb3RxNUpsczNpQUFObjVSRlVqbDNsVTVxek82MWZUZnExZFNF?=
 =?utf-8?B?RHdodlNPTmc0TVNETWNTRVpNSzUwTEJhS3FhS0FaUitRbG5tYXNTYy91a1JD?=
 =?utf-8?B?Z2IvZmYxNHJKMHd0MlZ2OFFjcU1yTGJxaXFSMk56QzFEUEh5MkFDK3cvQWNI?=
 =?utf-8?B?WTQvcTVTUjc3bHM4b0FDMnJYeE90MlExZzdhb1JKckZWOWN0dUQ3bFl3Q0NR?=
 =?utf-8?B?ZlBwK1FjaENSTFZKQTZyUmNEUFFiYlNMdUo4MExRSmNDQUVZZ1NGcmRBcG1H?=
 =?utf-8?B?enM2eGoyUytPZU9HbklPczNjVXdXSWM4czRKN3F4YnkrcmVkNE9IUVNzazdD?=
 =?utf-8?B?STIvSzFjdGM4VTI1dVVEVFdDQ05sUUFxMG9zSmMxY1ozaVVlMEdQVFRpd3lF?=
 =?utf-8?B?UUUwZ0hOMHpsNmVKL2ZsTlMwR2ZneVV1K1dPMnZGbldvbk9laHNJUlk4UU01?=
 =?utf-8?B?ODlBN1RRaTFqeDd0MUtDY2dCR2hkeTBNczRJZXNrbXhwUGZIVHZMMCtYNUlG?=
 =?utf-8?B?TTRuZlBWRWtadDhNZlFYSXBONDJJdkFYeUNVNHk1akhWamdrWnBYOFR5M3gz?=
 =?utf-8?B?VDk2VWdKZ21VRSt5dXhoQlUwVWlXYThUNEVXV1pWNkZJWS9IQ0ZzR1EyRnZP?=
 =?utf-8?B?WVkwT2VjYlVpZ3RTZlJxUkZHRG44eVY0cjZlRm82dHdWSVBzbXZ5UjBtU3lN?=
 =?utf-8?B?aHB3V2ZzaEl4OEpya0l4eEZ4UkozS2JEaXlBUXNUUng2MjIyeDVCdm5tTnBH?=
 =?utf-8?B?YXNKelp4T2ZTeHJlS2VPZkREdnA4OENYT0ZuSEVGQ1dRNm1RbWk4aGNYQkp2?=
 =?utf-8?B?U0VWaUsveGRUY0EyOUlvVzlXdk9PcEQ0REQ3Njl4aUk3d29qT0Nzd1RJZE5p?=
 =?utf-8?B?cUx4Y1FkZU5XVDNCRjg0VFZtSnZWVVd6dVYzdUVhZVBmTlduOVQ2eEd4SUht?=
 =?utf-8?B?cFRva2UvOVYrSEtCbXJGSUdDZzlWRWQzbkdlY1hwUUtudjV6N2VrdGJHdVBm?=
 =?utf-8?B?VkgyWU84NW9ud2E3YXEraHk0VENSa2lKSERoVDBNM0U5V1JYcHo3RjJlOEcw?=
 =?utf-8?B?TDBZYWltd05Da0FaMlJaMDJrVG80d1RHci96NjI2M3k3cVdNVFdJSTZrYlRy?=
 =?utf-8?B?RVAxelRzeHl4ay9ZZTZ3QU5wZHo1T01zcTVCdGhCNGFBOTZqY1RjODE3R2V0?=
 =?utf-8?B?amNVZ0NIT09vN3M4TjFtZ0JESFd1TDZZQ2Q5aWNYMVRoSHhwZWtjcHlHNm9D?=
 =?utf-8?B?L1ordmxxV0NkNGN2VEpzbnJNeWZhcmgyYlFjZDRpT0UzVGhycUlheExIZlRM?=
 =?utf-8?B?V2d1QXRSZ2IybkRWMndHR2VqYndKWU5MRUlTOFBPdCthd3FSZDJaS1pkQVhr?=
 =?utf-8?B?K0ZvOHFhTng5YUFXUzg0MFhCU2ZSTlBYVHgyYzc3ckxqMVdUSzR0TXltZkht?=
 =?utf-8?B?QlgyRWJrcmZyNEMveER6YzFZYjRqazZNOGZVYUFuOHJNSTdBTm8xcStaVFdK?=
 =?utf-8?Q?0bFyMvMjNvQAYiZ1xASIcifMF?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: f16260a9-99df-4959-981b-08dbfc11660a
X-MS-Exchange-CrossTenant-AuthSource: MN0PR12MB6101.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Dec 2023 19:26:26.0924
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: JgcW6o5YA04GeLCw2fimvee3fKT2zB+J5v9+vbDMGeuZw9DI1rKt+5am8ML4ggKb9ypcqe5XEfdcU98bh1dDZg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ2PR12MB8739

On 12/13/2023 06:45, Kalle Valo wrote:
> Mario Limonciello <mario.limonciello@amd.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.

In my case I could reproduce the behavior on my Unifi access points. 
I've got a few that devices could roam between.

I also happen to have a laptop on my desk with a WCN6855 that behaves 
just fine with those same APs.

The other people with problems I've asked to come to this thread to 
share more about their devices.

> 
>> 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?

It was just a data point in the original patch from Sultan (who is on 
CC).  I haven't corroborated it myself.  Once I saw that other kernel 
drivers like iwlwifi are also "defaulting" to off with a module 
parameter I figured it made sense to bring that for discussion.

> 
>> 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')

I'll experiment with an unpatched kernel just undoing this from here to 
see if it alone improves things.

> 
> * 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.
> 

Should we also discuss removing the iwlwifi one then too perhaps?
Seems incongruent to offer it for some drivers but not others.