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

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

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.

Regards,

Hans