On Sun, Oct 18, 2020 at 11:41 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Hi, > > On 10/16/20 4:51 PM, Rafael J. Wysocki wrote: > > On Fri, Oct 16, 2020 at 1:11 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> > >> <note folding the 2 threads we are having on this into one, adding every one from both threads to the Cc> > >> > >> Hi, > >> > >> On 10/14/20 5:42 PM, Rafael J. Wysocki wrote: > >>> On Wed, Oct 14, 2020 at 4:06 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >>>> On 10/14/20 3:33 PM, Rafael J. Wysocki wrote: > >> > >> <snip> > >> > >>>>> First, a common place to register a DPTF system profile seems to be > >>>>> needed and, as I said above, I wouldn't expect more than one such > >>>>> thing to be present in the system at any given time, so it may be > >>>>> registered along with the list of supported profiles and user space > >>>>> will have to understand what they mean. > >>>> > >>>> Mostly Ack, I would still like to have an enum for DPTF system > >>>> profiles in the kernel and have a single piece of code map that > >>>> enum to profile names. This enum can then be extended as > >>>> necessary, but I want to avoid having one driver use > >>>> "Performance" and the other "performance" or one using > >>>> "performance-balanced" and the other "balanced-performance", etc. > >>>> > >>>> With the goal being that new drivers use existing values from > >>>> the enum as much as possible, but we extend it where necessary. > >>> > >>> IOW, just a table of known profile names with specific indices assigned to them. > >> > >> Yes. > >> > >>> This sounds reasonable. > >>> > >>>>> Second, irrespective of the above, it may be useful to have a > >>>>> consistent way to pass performance-vs-power preference information > >>>>> from user space to different parts of the kernel so as to allow them > >>>>> to adjust their operation and this could be done with a system-wide > >>>>> power profile attribute IMO. > >>>> > >>>> I agree, which is why I tried to tackle both things in one go, > >>>> but as you said doing both in 1 API is probably not the best idea. > >>>> So I believe we should park this second issue for now and revisit it > >>>> when we find a need for it. > >>> > >>> Agreed. > >>> > >>>> Do you have any specific userspace API in mind for the > >>>> DPTF system profile selection? > >>> > >>> Not really. > >> > >> So before /sys/power/profile was mentioned, but that seems more like > >> a thing which should have a set of fixed possible values, iow that is > >> out of scope for this discussion. > > > > Yes. > > > >> Since we all seem to agree that this is something which we need > >> specifically for DPTF profiles maybe just add: > >> > >> /sys/power/dptf_current_profile (rw) > >> /sys/power/dptf_available_profiles (ro) > >> > >> (which will only be visible if a dptf-profile handler > >> has been registered) ? > >> > >> Or more generic and thus better (in case other platforms > >> later need something similar) I think, mirror the: > >> > >> /sys/bus/cpu/devices/cpu#/cpufreq/energy_performance_* bits > >> for a system-wide energy-performance setting, so we get: > >> > >> /sys/power/energy_performance_preference > >> /sys/power/energy_performance_available_preferences > > > > But this is not about energy vs performance only in general, is it? > > > >> (again only visible when applicable) ? > >> > >> I personally like the second option best. > > > > But I would put it under /sys/firmware/ instead of /sys/power/ and I > > would call it something like platform_profile (and > > platform_profile_choices or similar). > > Currently we only have dirs under /sys/firmware: > > [hans@x1 ~]$ ls /sys/firmware > acpi dmi efi memmap > > But we do have /sys/firmware/apci/pm_profile: > > Documentation/ABI/stable/sysfs-acpi-pmprofile > > What: /sys/firmware/acpi/pm_profile > Date: 03-Nov-2011 > KernelVersion: v3.2 > Contact: linux-acpi@xxxxxxxxxxxxxxx > Description: The ACPI pm_profile sysfs interface exports the platform > power management (and performance) requirement expectations > as provided by BIOS. The integer value is directly passed as > retrieved from the FADT ACPI table. > Values: For possible values see ACPI specification: > 5.2.9 Fixed ACPI Description Table (FADT) > Field: Preferred_PM_Profile > > Currently these values are defined by spec: > 0 Unspecified > 1 Desktop > 2 Mobile > 3 Workstation > 4 Enterprise Server > ... > > Since all platforms which we need this for are ACPI based > (and the involved interfaces are also all ACPI interfaces) > how about: > > /sys/firmware/acpi/platform_profile > /sys/firmware/acpi/platform_profile_choices > > ? > > I think this goes nice together with /sys/firmware/acpi/pm_profile > although that is read-only and this is a read/write setting. > > Rafel, would: > > /sys/firmware/acpi/platform_profile > /sys/firmware/acpi/platform_profile_choices > > work for you ? Yes, it would. Cheers!
