linux-kernel - Re: [PATCH v5 2/5] tick: Add freeze timer events

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Date:   Sat, 8 Jul 2017 19:05:37 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Derek Basehore <dbasehore@...omium.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v5 2/5] tick: Add freeze timer events

On Sat, Jul 8, 2017 at 3:03 AM, Derek Basehore <dbasehore@...omium.org> wrote:
> Adds a new feature to tick to schedule wakeups on a CPU during freeze.
> This won't fully wake up the system (devices are not resumed), but
> allow simple platform functionality to be run during freeze with
> little power impact.
>
> This implementation allows an idle driver to setup a timer event with
> the clock event device when entering freeze by calling
> tick_set_freeze_event. Only one caller should exist for the function.
>
> tick_freeze_event_expired is used to check if the timer went off when
> the CPU wakes.
>
> The event is cleared by tick_clear_freeze_event.

> +int tick_set_freeze_event(int cpu, ktime_t delta)
> +{

> +               printk_deferred(KERN_WARNING
> +                               "[%s] unsupported by clock event device\n",

Can it be one line?

> +               printk_deferred(KERN_WARNING
> +                               "[%s] clock event device in use\n",

Ditto.

> +               printk_deferred(KERN_WARNING
> +                               "[%s] %lluns outside range: [%lluns, %lluns]\n",

Ditto.

> +               printk_deferred(KERN_WARNING
> +                               "Failed to program freeze event\n");

Ditto.

> +int tick_freeze_event_expired(int cpu)
> +{
> +       struct clock_event_device *dev = per_cpu(tick_cpu_device, cpu).evtdev;
> +
> +       if (!(dev && dev->event_expired))

Usually we use a pattern (!x || !x->y). At least for me it looks
slightly better to read.

> +               return 0;
> +
> +       return dev->event_expired(dev);
> +}

-- 
With Best Regards,
Andy Shevchenko