linux-kernel - Re: [RFD] Remove the userspace governor and the cooling device set state sysfs entry

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Message-ID: <a3f2807b-0d67-b159-430b-33be22409179@arm.com>
Date:   Fri, 1 Oct 2021 12:11:50 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Zhang Rui <rui.zhang@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: [RFD] Remove the userspace governor and the cooling device set
 state sysfs entry



On 10/1/21 11:30 AM, Daniel Lezcano wrote:
> 
> Hi Lukasz,
> 
> On 30/09/2021 12:10, Lukasz Luba wrote:
>> Hi Daniel,
>>
>> On 9/22/21 10:59 AM, Daniel Lezcano wrote:
>>>
>>> Hi,
>>>
>>> the userspace governor is sending temperature when polling is active and
>>> trip point crossed events. Nothing else.
>>>
>>> In the other side, the cooling device have their cooling device
>>> set_cur_state read-writable all the time.
>>>
>>> The thermal framework is wrongly used by userspace as a power capping
>>> framework by acting on the cooling device opaque state. This one then
>>> competes with the in-kernel governor decision.
>>>
>>> As the new netlink thermal notification is able to provide the same
>>> information than the userspace governor.
>>>
>>> I propose to remove the userspace governor and the cur_state entry in
>>> the sysfs exported file.
>>>
>>> The DTPM framework is the right framework to do power capping and
>>> moreover it deals with the aggregation via the dev pm qos.
>>>
>>> Does it make sense ?
>>
>> It sounds that we should be OK with the information from netlink.
>> I don't see objections. We can also extend the netlink packet when
>> needed. I'm fine with removing the user-space governor.
> 
> thank you for your answer. I'll propose a patch with a warn when the
> userspace governor is registered in order to let know people the
> governor is deprecated.
> 
> Probably, it would make sense to emit a warning also when the cooling
> device state is set from userspace.
> 
> For the next release, we should be able to drop the userspace governor
> and make the cooling device state read-only.
> 
> Does it make sense ?
> 
> 

Yes, it makes sense.