On 2025/1/16 19:39, Russell Haley wrote: > Hello, > > I noticed something here just as a user casually browsing the mailing list. > > On 1/13/25 6:21 AM, Lifeng Zheng wrote: >> Add sysfs interfaces for CPPC autonomous selection in the cppc_cpufreq >> driver. >> >> Signed-off-by: Lifeng Zheng <zhenglifeng1@xxxxxxxxxx> >> --- >> .../ABI/testing/sysfs-devices-system-cpu | 54 +++++++++ >> drivers/cpufreq/cppc_cpufreq.c | 109 ++++++++++++++++++ >> 2 files changed, 163 insertions(+) >> >> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu >> index 206079d3bd5b..3d87c3bb3fe2 100644 >> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu >> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu >> @@ -268,6 +268,60 @@ Description: Discover CPUs in the same CPU frequency coordination domain >> This file is only present if the acpi-cpufreq or the cppc-cpufreq >> drivers are in use. >> > > [...snip...] > >> +What: /sys/devices/system/cpu/cpuX/cpufreq/energy_perf >> +Date: October 2024 >> +Contact: linux-pm@xxxxxxxxxxxxxxx >> +Description: Energy performance preference >> + >> + Read/write an 8-bit integer from/to this file. This file >> + represents a range of values from 0 (performance preference) to >> + 0xFF (energy efficiency preference) that influences the rate of >> + performance increase/decrease and the result of the hardware's >> + energy efficiency and performance optimization policies. >> + >> + Writing to this file only has meaning when Autonomous Selection is >> + enabled. >> + >> + This file only presents if the cppc-cpufreq driver is in use. > > In intel_pstate driver, there is file with near-identical semantics: > > /sys/devices/system/cpu/cpuX/cpufreq/energy_performance_preference > > It also accepts a few string arguments and converts them to integers. > > Perhaps the same name should be used, and the semantics made exactly > identical, and then it could be documented as present for either > cppc_cpufreq OR intel_pstate? > > I think would be more elegant if userspace tooling could Just Work with > either driver. > > One might object that the frequency selection behavior that results from > any particular value of the register itself might be different, but they > are *already* different between Intel's P and E-cores in the same CPU > package. (Ugh.) Yes, I should use the same name. Thanks. As for accepting string arguments and converting them to integers, I don't think it is necessary. It'll be a litte confused if someone writes a raw value and reads a string I think. I prefer to let users freely set this value. In addition, there are many differences between the implementations of energy_performance_preference in intel_pstate and cppc_cpufreq (and amd-pstate...). It is really difficult to explain all this differences in this document. So I'll leave it to be documented as present for cppc_cpufreq only. > > -- > Thanks, > Russell > > >
