Re: [RFC][PATCH] cpuidle: Consolidate disabled state checks

Daniel Lezcano
2019-09-04T21:54:55Z

Hi Rafael,

On 04/09/2019 12:41, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> There are two reasons why CPU idle states may be disabled: either
> because the driver has disabled them or because they have been
> disabled by user space via sysfs.
>
> In the former case, the state's "disabled" flag is set once during
> the initialization of the driver and it is never cleared later (it
> is read-only effectively). In the latter case, the "disable" field
> of the given state's cpuidle_state_usage struct is set and it may be
> changed via sysfs. Thus checking whether or not an idle state has
> been disabled involves reading these two flags every time.
>
> In order to avoid the additional check of the state's "disabled" flag
> (which is effectively read-only anyway), use the value of it at the
> init time to set a (new) flag in the "disable" field of that state's
> cpuidle_state_usage structure and use the sysfs interface to
> manipulate another (new) flag in it. This way the state is disabled
> whenever the "disable" field of its cpuidle_state_usage structure is
> nonzero, whatever the reason, and it is the only place to look into
> to check whether or not the state has been disabled.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> I have not tested this yet, hence RFC, so it is mainly for feedback.

This change makes sense.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

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