[PATCH v8 6/6] cpufreq: powernv: Add sysfs attributes to show throttle stats
viresh.kumar at linaro.org
Wed Feb 3 20:03:57 AEDT 2016
On 03-02-16, 14:12, Shilpasri G Bhat wrote:
> I need the chip-id in the <attr>_show(). With just sysfs_create_group() I will
> get the cpufreq_global_kobject in the <attr>_show() and I will not be able to
> figure out the chip-id.
The more I look at it, the more I am convinced that keeping this
'chip' directory in /sys/devices/system/cpu/cpuX/cpufreq/ makes sense.
So, here is the deal:
- A 'chip' on your platforms can contain multiple group of CPUs, which
are represented by policies in cpufreq core. i.e. A chip can have
- All CPUs present on the same chip are subject to same throttling
- Right now you are putting the 'chip' directory in cpu/cpufreq/
directory. Because that directory isn't specific to a policy, but
entire cpufreq subsystem, you can't get a policy->cpu in the code
for the kobject in question. And so you are *forced* to create a
kobject, so that you can do container_of() and get chip->id.
- And then you also need to unnecessarily add another field in the
chip directory 'chip_mask', that is nothing but an bitwise OR
operation on policy->related_cpus, so that userspace can know which
policies/CPUs are managed by the 'chip'.
What I can suggest is:
- Move this directory inside cpuX/cpufreq/ directory, in a similar way
as to how we create 'stats' directory today.
- You can then get policy->cpu, to get chip->id out of it.
- The only disadvantage here is that the same chip directory will be
replicated in multiple policies, but that makes it more readable.
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