linux-kernel - Re: [patch 3/3] clockevent driver for arm/pxa2xx

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Date:	Fri, 19 Jan 2007 20:33:40 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	Luotao Fu <lfu@...gutronix.de>
Subject: Re: [patch 3/3] clockevent driver for arm/pxa2xx

On Fri, 2007-01-19 at 20:13 +0100, Guennadi Liakhovetski wrote:
> > +static u32 clockevent_mode = 0;
> > +
> > +static void pxa_set_next_event(unsigned long evt,
> > +				  struct clock_event_device *unused)
> > +{
> > +	OSMR0 = OSCR + evt;
> > +}
> 
> This doesn't work for me in various nasty ways. Please, check for a 
> minimum delay or loop to get ahead of time. See code in the "old" timer 
> ISR. See how it unconditionally adds at least 10 ticks...

I added support for match register based devices and you want to do
something like this:

static int hpet_next_event(unsigned long delta,
                           struct clock_event_device *evt)
{
        unsigned long cnt;

        cnt = hpet_readl(HPET_COUNTER);
        cnt += delta;
        hpet_writel(cnt, HPET_T0_CMP);

        return ((long)(hpet_readl(HPET_COUNTER) - cnt ) > 0);
}

The generic code takes care of the already expired event.

	tglx


	

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