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). Cheers!
