linux-kernel - Re: [PATCH 2/6] cpufreq: Replace few CPUFREQ_CONST_LOOPS checks with has

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Date:   Wed, 19 Jun 2019 14:20:18 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] cpufreq: Replace few CPUFREQ_CONST_LOOPS checks with has_target()

On Wed, Jun 19, 2019 at 1:36 PM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> CPUFREQ_CONST_LOOPS was introduced in a very old commit from pre-2.6
> kernel release commit 6a4a93f9c0d5 ("[CPUFREQ] Fix 'out of sync'
> issue").
>
> Probably the initial idea was to just avoid these checks for set_policy
> type drivers and then things got changed over the years. And it is very
> unclear why these checks are there at all.
>
> Replace the CPUFREQ_CONST_LOOPS check with has_target(), which makes
> more sense now.
>
> Also remove () around freq comparison statement as they aren't required
> and checkpatch also warns for them.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 54befd775bd6..e59194c2c613 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -359,12 +359,10 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy,
>                  * which is not equal to what the cpufreq core thinks is
>                  * "old frequency".
>                  */
> -               if (!(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
> -                       if (policy->cur && (policy->cur != freqs->old)) {
> -                               pr_debug("Warning: CPU frequency is %u, cpufreq assumed %u kHz\n",
> -                                        freqs->old, policy->cur);
> -                               freqs->old = policy->cur;
> -                       }
> +               if (has_target() && policy->cur && policy->cur != freqs->old) {
> +                       pr_debug("Warning: CPU frequency is %u, cpufreq assumed %u kHz\n",
> +                                freqs->old, policy->cur);
> +                       freqs->old = policy->cur;

Is cpufreq_notify_transition() ever called if ->setpolicy drivers are in use?

>                 }
>
>                 srcu_notifier_call_chain(&cpufreq_transition_notifier_list,
> @@ -1618,8 +1616,7 @@ static unsigned int __cpufreq_get(struct cpufreq_policy *policy)
>         if (policy->fast_switch_enabled)
>                 return ret_freq;
>
> -       if (ret_freq && policy->cur &&
> -               !(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
> +       if (has_target() && ret_freq && policy->cur) {
>                 /* verify no discrepancy between actual and
>                                         saved value exists */
>                 if (unlikely(ret_freq != policy->cur)) {
> --
> 2.21.0.rc0.269.g1a574e7a288b
>