Re: [External] Re: [RFC] ACPI: platform-profile: support for AC vs DC modes

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 3/14/22 16:32, Mark Pearson wrote:
> 
> 
> On 2022-03-14 11:31, Hans de Goede wrote:
>> Hi,
>>
>> On 3/14/22 15:43, Hans de Goede wrote:
>>> Hi Mario,
>>>
>>> On 3/14/22 14:39, Limonciello, Mario wrote:
>>>> [Public]
>>>>
>>>>>>
>>>>>> I cycled through a few different implementations but came down on what I
>>>>>> proposed. I considered 6 values - but I don't think that makes sense and
>>>>>> makes it overall more complicated than it needs to be and less flexible.
>>>>>
>>>>> Ah, so to be clear, my 2 scenarios above were theoretical scenarios,
>>>>> because I'm wondering how the firmware API here actually looks like,
>>>>> something which so far is not really clear to me.
>>>>>
>>>>> When you say that you considered using 6 values, then I guess that
>>>>> the firmware API actually offers 6 values which we can write to a single slot:
>>>>> ac-low-power,dc-lowpower,ac-balanced,dc-balanced,ac-performance,dc-
>>>>> performance
>>>>>
>>>>> ?
>>>>>
>>>>> But that is not what the RFC patch that started this thread shows at all,
>>>>> the API to the driver is totally unchanged and does not get passed
>>>>> any info on ac/dc selection ?  So it seems to me that the ACPI API Linux
>>>>> uses for this writes only 1 of 3 values to a single slot and the EC automatically
>>>>> switches between say ac-balanced and dc-balanced internally.
>>>>>
>>>>> IOW there really being 2 differently tuned balance-profiles is not visible to
>>>>> the OS at all, this is handled internally inside the EC, correct ?
>>>>>
>>>>
>>>> No - on Lenovo's platform there are 6 different profiles that can be selected
>>>> from the kernel driver.  3 are intended for use on battery, 3 are intended for
>>>> use on AC.
>>>
>>> Ah, I already got that feeling from the rest of the thread, so I reread
>>> Mark's RFC again before posting my reply today and the RFC looked like
>>> the same 3 profiles were being set and the only functionality added
>>> was auto profile switching when changing between AC/battery.
>>>
>>> Thank you for clarifying this. Having 6 different stories
>>> indeed is a very different story.
>>>
>>>>> Otherwise I would expect the kernel internal driver API to also change and
>>>>> to also see a matching thinkpad_acpi patch in the RFC series?
>>>>
>>>> The idea I see from Mark's thread was to send out RFC change for the platform profile
>>>> and based on the direction try to implement the thinkpad-acpi change after that.
>>>>
>>>> Because of the confusion @Mark I think you should send out an RFC v2 with thinkpad acpi
>>>> modeled on top of this the way that you want.
>>>
>>> I fully agree and since you introduce the concept of being on AC/battery to the
>>> drivers/acpi/platform_profile.c cpde, please change the 
>>> profile_set and profile_get function prototypes in struct platform_profile_handler
>>> to also take a "bool on_battery" extra argument and use that in the thinkpad
>>> driver to select either the ac or the battery tuned low/balanced/performance 
>>> profile.
>>>
>>> And please also include an update to Documentation/ABI/testing/sysfs-platform_profile
>>> in the next RFC.
>>>
>>> Also notice how I've tried to consistently use AC/battery in my last reply,
>>> DC really is not a good term for "on battery". AC also is sort of dubious
>>> for "connected to an external power-supply" but its use for that is sorta
>>> common and it is nice and short.
>>
>> One last request for the v2 RFC, please also Cc Bastien Nocera, so that
>> he can take a look at the proposed uapi changes from the userspace side
>> of things.
>>
> Ack - will do.

So I've been thinking a bit more about this while I was outside for some
fresh air.

First of all let me say that I do agree that the having in essence 6
different profiles thing needs a kernel solution.

What I'm not entirely sure about is if this needs to be something
generic, with a new userspace-API as you proposed in the v1 RFC,
or if it would be better to just solve this in thinkpad_acpi.c .

Now that I've a better grasp of the problem, I'll start a new email
thread on this tomorrow with all the various take-holders in the Cc
to try and answer that question.

It probably is a good idea to wait with doing a v2 of the RFC until
we've had that discussion...

Regards,

Hans