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SubjectRe: [PATCH v2 1/4] PM / EM: add devices to Energy Model
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On 06/02/2020 14:46, lukasz.luba@arm.com wrote:
> From: Lukasz Luba <lukasz.luba@arm.com>

[..]

> @@ -26,7 +28,7 @@ framework, and interested clients reading the data from it::

s/::/: ?

> | Thermal (IPA) | | Scheduler (EAS) | | Other |
> +---------------+ +-----------------+ +---------------+
> | | em_pd_energy() |
> - | | em_cpu_get() |
> + | em_get_pd() | em_cpu_get() |
> +---------+ | +---------+

em_get_pd() and em_cpu_get()? Why not em_pd_get()? em_cpu_get() is a
specific em_get_pd(). right?

[...]

> @@ -85,13 +89,20 @@ API.
> 2.3 Accessing performance domains
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> +There is two API functions which provide the access to the energy model:
> +em_cpu_get() which takes CPU id as an argument and em_get_pd() with device
> +pointer as an argument. It depends on the subsystem which interface it is
> +going to use, but in case of CPU devices both functions return the same
> +performance domain.

There is probably a reason why we need this specific function for CPU
devices? The reason should be described. People might ask why
em_get_pd() is not sufficient.

[...]

> - * A "performance domain" represents a group of CPUs whose performance is
> - * scaled together. All CPUs of a performance domain must have the same
> - * micro-architecture. Performance domains often have a 1-to-1 mapping with
> - * CPUFreq policies.
> + * In case of CPU device, a "performance domain" represents a group of CPUs
> + * whose performance is scaled together. All CPUs of a performance domain
> + * must have the same micro-architecture. Performance domains often have
> + * a 1-to-1 mapping with CPUFreq policies.
> + * In case of other devices the 'priv' field is unused.
> */
> struct em_perf_domain {
> - struct em_cap_state *table;
> - int nr_cap_states;
> - unsigned long cpus[0];
> + struct em_perf_state *table;
> + int nr_perf_states;
> + void *priv;

In case you go back to the variable length field plus type field to
distingush EM devices, keep cpus[0] as the name.

[..]

> /**
> - * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf. domain
> + * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf.
> + domain

Why this change?

[...]

> @@ -141,12 +210,12 @@ static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
> */
> opp_eff = freq / power;
> if (opp_eff >= prev_opp_eff)
> - pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
> - cpu, i, i - 1);
> + dev_warn(dev, "energy_model: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",

s/energy_model/EM ?

[...]

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