linux-kernel - Re: [PATCH 3/7] cpufreq: Only query drivers that implement cpufreq

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Message-ID: <CAOh2x=nXQrgwm2Jw88GjQe-fjpJrK+cjTWd-vK377UEBeXGu3w@mail.gmail.com>
Date:	Wed, 6 Feb 2013 07:17:16 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	dirk.brandewie@...il.com
Cc:	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: Re: [PATCH 3/7] cpufreq: Only query drivers that implement cpufreq_driver.target()

On Tue, Feb 5, 2013 at 11:54 PM,  <dirk.brandewie@...il.com> wrote:
> From: Dirk Brandewie <dirk.brandewie@...il.com>
>
> Scaling drivers that implement cpufreq_driver.setpolicy() have
> internal governors and may/will change the current operating frequency
> very frequently this will cause cpufreq_out_of_sync() to be called
> every time. Only call cpufreq_driver.get() for drivers that implement
> cpufreq_driver.target()
>
> Signed-off-by: Dirk Brandewie <dirk.j.brandewie@...el.com>
> ---
>  drivers/cpufreq/cpufreq.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 96bc302..d8daa4b 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1787,7 +1787,7 @@ int cpufreq_update_policy(unsigned int cpu)
>
>         /* BIOS might change freq behind our back
>           -> ask driver for current freq and notify governors about a change */
> -       if (cpufreq_driver->get) {
> +       if (cpufreq_driver->get && cpufreq_driver->target) {
>                 policy.cur = cpufreq_driver->get(cpu);
>                 if (!data->cur) {
>                         pr_debug("Driver did not initialize current freq");

I am really not liking copy-pasting my older comments here :(

"This would mean policy->cur has a garbage value. I don't really know
how would other routine behave on this. Would it make sense to make
policy->cur zero atleast?
"
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