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ACPI / CPPC: add sysfs support to compute delivered performance

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The CPPC tables contain entries for per CPU feedback counters which
allows us to compute the delivered performance over a given interval
of time.

The math for delivered performance per the CPPCv5.0+ spec is:
  reference perf * delta(delivered perf ctr)/delta(ref perf ctr)

Maintaining deltas of the counters in the kernel is messy, as it
depends on when the reads are triggered. (e.g. via the cpufreq
->get() interface). Also the ->get() interace only returns one
value, so cant return raw values. So instead, leave it to userspace
to keep track of raw values and do its math for CPUs it cares about.

delivered and reference perf counters are exposed via the same
sysfs file to avoid the potential "skid", if these values are read
individually from userspace.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Ashwin Chaugule 2016-08-16 14:39:42 -06:00 • committed by Rafael J. Wysocki
parent be8b88d7d9
commit 158c998ea4
2 changed files with 120 additions and 21 deletions
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6
include/acpi/cppc_acpi.h
View file

@ -65,6 +65,7 @@ struct cpc_desc {
int write_cmd_id;
struct cpc_register_resource cpc_regs[MAX_CPC_REG_ENT];
struct acpi_psd_package domain_info;
struct kobject kobj;
};
/* These are indexes into the per-cpu cpc_regs[]. Order is important. */
@ -99,7 +100,6 @@ enum cppc_regs {
struct cppc_perf_caps {
u32 highest_perf;
u32 nominal_perf;
u32 reference_perf;
u32 lowest_perf;
};
@ -111,9 +111,9 @@ struct cppc_perf_ctrls {
struct cppc_perf_fb_ctrs {
u64 reference;
u64 prev_reference;
u64 delivered;
u64 prev_delivered;
u64 reference_perf;
u64 ctr_wrap_time;
};
/* Per CPU container for runtime CPPC management. */