Re: [PATCH v2 1/2] cpufreq: Add exit_prepare callback to cpufreq_driver interface

From: Rafael J. Wysocki
Date: Fri Mar 14 2014 - 21:49:40 EST


On Friday, March 14, 2014 02:03:56 PM dirk.brandewie@xxxxxxxxx wrote:
> From: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
>
> This callback allows the driver to do clean up before the CPU is
> completely down and its state cannot be modified. This is used
> by the intel_pstate driver to reduce the requested P state prior to
> the core going away. This is required because the requested P state
> of the offline core is used to select the package P state. This
> effectively sets the floor package P state to the requested P state on
> the offline core.
>
> Signed-off-by: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
> ---
> Documentation/cpu-freq/cpu-drivers.txt | 8 +++++++-
> drivers/cpufreq/cpufreq.c | 3 +++
> include/linux/cpufreq.h | 1 +
> 3 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt
> index 8b1a445..79def80 100644
> --- a/Documentation/cpu-freq/cpu-drivers.txt
> +++ b/Documentation/cpu-freq/cpu-drivers.txt
> @@ -61,7 +61,13 @@ target_index - See below on the differences.
>
> And optionally
>
> -cpufreq_driver.exit - A pointer to a per-CPU cleanup function.
> +cpufreq_driver.exit - A pointer to a per-CPU cleanup
> + function called during CPU_POST_DEAD
> + phase of cpu hotplug process.
> +
> +cpufreq_driver.stop - A pointer to a per-CPU stop function
> + called during CPU_DOWN_PREPARE phase of
> + cpu hotplug process.
>
> cpufreq_driver.resume - A pointer to a per-CPU resume function
> which is called with interrupts disabled
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index cf485d9..0d430d7 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1338,6 +1338,9 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
> }
> }
>
> + if (cpufreq_driver->stop)

What about doing

+ if (cpufreq_driver->setpolicy && cpufreq_driver->stop)

here instead? That would make it clear where the new callback belongs.

If you're fine with that, I can make that change when applying the patch.

> + cpufreq_driver->stop(policy);
> +
> return 0;
> }
>
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 4d89e0e..ff8db19 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -224,6 +224,7 @@ struct cpufreq_driver {
> int (*bios_limit) (int cpu, unsigned int *limit);
>
> int (*exit) (struct cpufreq_policy *policy);
> + int (*stop) (struct cpufreq_policy *policy);
> int (*suspend) (struct cpufreq_policy *policy);
> int (*resume) (struct cpufreq_policy *policy);
> struct freq_attr **attr;
>

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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