RE: [RFC] Documentation: Add documentation for new performance_profile sysfs class

[Limonciello, Mario]

> As far as I know, the profiles affect  the thermal behavior like "how long to
> wait before starting the fan and at what temperature" or "how fast to run the
> fan with the current cpu load and temperature".
> 
> The only way that firmware uses to "control" performance should be the odvp0
> DPTF variable.
> 
> On Windows HP expose  both "Cool" and "Quiet" profile respectively as "Ideal
> for when the computer feels warm to the touch" and "Ideal for quiet
> environments".
> 
> more detail: https://support.hp.com/in-en/document/c06063108
> 
> To be precise "Quiet" profile should be available only on platform without
> dedicate GPU (I'm investigating if there is other case), instead the other 3
> profiles ("HP Recommended", "Performance" and "Cool") are available on all
> platform that support thermal profile.
> 
> reading here seems that Dell offer identical profiles:
> https://www.dell.com/support/manuals/it/it/itbsdt1/dell-command-power-manager-
> v2.2/userguide_dell/thermal-management?guid=guid-c05d2582-fc07-4e3e-918a-
> 965836d20752&lang=en-us
> 

The Dell profiles here I don't think should be conflated with DTT/DPTF though.
These won't affect anything in the DTT vault.

Those profiles are already accessible from Linux userland, there is already a
command line tool in libsmbios that can do it.

$ sudo smbios-thermal-ctl -i
Libsmbios version : 2.4.3
smbios-thermal-ctl version : 2.4.3

 Print all the Available Thermal Information of your system:
-------------------------------------------------------------------

Supported Thermal Modes:
         Balanced
         Cool Bottom
         Quiet
         Performance

Supported Active Acoustic Controller (AAC) modes:

Supported AAC Configuration type:
        Global (AAC enable/disable applies to all supported USTT modes)\

$ sudo smbios-thermal-ctl -g
Helper function to Get current Thermal Mode settings

 Print Current Status of Thermal Information:
-------------------------------------------------------------------

Current Thermal Modes:
         Balanced

Current Active Acoustic Controller (AAC) Mode:
         AAC mode Disabled

Current Active Acoustic Controller (AAC) Mode:
        Global (AAC enable/disable applies to all supported USTT modes)

---
*If* we choose to export them for Dell from the kernel, we should probably also
filter from kernel side and modify the existing userspace tool to use the kernel
API when possible.

I'm not convinced that Dell would want to tie into this proposed knob with those
settings because I expect that existing software like thermald will not work as
efficiently.