On Mon, 2019-03-04 at 22:57 +0100, Rafael J. Wysocki wrote: > On Mon, Mar 4, 2019 at 7:06 PM Srinivas Pandruvada > <srinivas.pandruv...@linux.intel.com> wrote: > > > > [...] > > > > There are other methods like PL1 budget limit for such cases. > > > > FW > > > > can > > > > just change the config TDP level. > > > > > > OK, but that would be done without notification I suppose? > > > > There is a notification via processor PCI device (B0D4). This is > > passed > > to user space to change the power limits. The new element is called > > PPCC and it is exposed via sysfs. > > What do you mean by "new element" and how exactly is it exposed? This is part of DPTF processor ACPI object (INT3401 or B0D4). They are exposed in sysfs E.g, /sys/bus/platform/devices/INT3401:00/power_limits/ There is a thermal uevent sent when they change. Both dptf daemon and thermald listen and use to set rapl power-constraints including step sizes for control. Someone can write a udev rule to do the same.
> > > Disabling turbo is not very interesting as there can be more turbo > > than > > non turbo. So you loose lots of performance. So instead you can > > control > > power in turbo region to give you more control. _PPC is even less > > interesting as you can't control uncore power. > > I guess that designers should know about that. The kernel is on the > receiving end here. :-) I think they know. Hence you don't see this issue of enable/disable of turbo by firmware quite often. This laptop here I guess released in beginning of 2014 with Haswell. > > > > [...] > > I guess that you are talking about intel_pstate_update_max_freq() > which acquires policy->rwsem. If so, what exactly is the problem > with > it? I was suggesting to use an API/define in cpufreq.h which does operation on policy->rwsem for better abstraction. This is the first time it was used outside core cpufreq.c. As more places it will be used in future, common function will help debug, if in some path there is a bug in aquire/release of semaphore. But you can ignore this. Thanks, Srinivas
