linux-kernel - Re: [PATCH v10 3/7] x86/time: read_boot

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Date:   Mon, 18 Jun 2018 11:42:30 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     pasha.tatashin@...cle.com
Cc:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux@...linux.org.uk, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, john.stultz@...aro.org,
        sboyd@...eaurora.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        douly.fnst@...fujitsu.com, peterz@...radead.org, prarit@...hat.com,
        feng.tang@...el.com, pmladek@...e.com, gnomes@...rguk.ukuu.org.uk
Subject: Re: [PATCH v10 3/7] x86/time: read_boot_clock64() implementation

On Fri, Jun 15, 2018 at 8:48 PM Pavel Tatashin
<pasha.tatashin@...cle.com> wrote:
>
> read_boot_clock64() returns time of when system was started. Now, that
> early boot clock is going to be available on x86 it is possible to
> implement x86 specific version of read_boot_clock64() that takes advantage
> of this new feature.

> +void __init read_boot_clock64(struct timespec64 *now, struct timespec64 *ts)
> +{
> +       u64 ns_boot = sched_clock_cpu(smp_processor_id());
> +       bool valid_clock;
> +       u64 ns_now;
> +
> +       ns_now = timespec64_to_ns(now);
> +       valid_clock = ns_boot && timespec64_valid_strict(now) &&
> +                       (ns_now > ns_boot);
> +

> +       if (!valid_clock)
> +               *ts = (struct timespec64){0, 0};
> +       else
> +               *ts = ns_to_timespec64(ns_now - ns_boot);



> +}


--
With Best Regards,
Andy Shevchenko