Messages in this thread | | | Subject | Re: [External] RE: [RFC] Documentation: Add documentation for new performance_profile sysfs class | From | Mark Pearson <> | Date | Mon, 5 Oct 2020 13:46:47 -0400 |
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On 2020-10-05 12:56 p.m., Limonciello, Mario wrote: >>> >>> When implemented for the two vendors mentioned here, it would be using a >>> proprietary "firmware API" implemented by those two vendors. For example >> write >>> arguments (0x1, 0x2) to ACPI-WMI method WMFT and it will cause firmware to >> coordinate >>> using undisclosed protocol to affect the platform changes desirable. >>> >>> This is different in my mind from "kernel writes to a specific register" to >> set >>> power properties of a specific device. >>> >> >> Just curious on this point - isn't that (mostly) what all hardware does? >> You write to it and the device does "stuff" to achieve the required >> effect. Yes this is in proprietary firmware, but from my experience with >> hardware devices that's not uncommon these days anyway. >> > > Yes I agree. Even "register" writes to a device are actually an API and > something in the hardware monitors those registers and does something as a > result. > >> Let me know if I'm misunderstanding something here. I couldn't see the >> difference between a register written to via ACPI and one written to via >> some other protocol (SMBUS? or whatever) >> >> Mark >> > > The reason I'm calling out a distinction here is that "platform" and "device" > can cover a lot more things. In this case it's an API provided by the platform's > firmware, not an individual device's firmware. So you can't actually guarantee > what the platform's firmware did. It could have sent any number of sideband > commands to devices that it controls. The "platform" could have potentially > told the GPU to turn up its fans, or lower it's clock as a result of this, but you > can't possibly know. > > However if we go the GPU example alone, it's a specific single device you're > controlling. You put the GPU into the characterization that you expected and it > operates that way. > Got it - fair enough :) Thanks for the explain. Thanks Mark
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