linux-kernel - Re: [PATCH 1/3] clocksource: davinci: work around a clocksource problem on dm365 SoC

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Message-ID: <CAMRc=McRKwYkUcY9J8cEkwoMnGYxs7SkTnOnFsVMDZD2DkJ1Zw@mail.gmail.com>
Date:   Tue, 17 Dec 2019 09:00:44 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     David Lechner <david@...hnology.com>
Cc:     Sekhar Nori <nsekhar@...com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kevin Hilman <khilman@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 1/3] clocksource: davinci: work around a clocksource
 problem on dm365 SoC

pon., 16 gru 2019 o 18:58 David Lechner <david@...hnology.com> napisał(a):
>
> >
> > +static unsigned int davinci_clocksource_tim32_mode;
>
> static unsigned bool davinci_clocksource_initialized;
>
> > +
> >   static struct davinci_clockevent *
> >   to_davinci_clockevent(struct clock_event_device *clockevent)
> >   {
> > @@ -94,7 +96,7 @@ static void davinci_tim12_shutdown(void __iomem *base)
> >        * halves. In this case TIM34 runs in periodic mode and we must
> >        * not modify it.
> >        */
> > -     tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC <<
> > +     tcr |= davinci_clocksource_tim32_mode <<
> >               DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
>
>         if (davinci_clocksource_initialized)
>                 tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC <<
>                         DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;

I thought about doing this initially, but then figured this code would
be called a lot, so why not avoid branching and just store the right
value? Alternatively we can do:

    if (likely(davinci_clocksource_initialized)
        ....

Bart