linux-kernel - Re: [PATCH] clocksource: em

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Date:	Mon, 7 May 2012 21:10:07 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Magnus Damm <magnus.damm@...il.com>
cc:	linux-kernel@...r.kernel.org, horms@...ge.net.au, arnd@...db.de,
	linux-sh@...r.kernel.org, johnstul@...ibm.com, rjw@...k.pl,
	lethal@...ux-sh.org, gregkh@...uxfoundation.org, olof@...om.net
Subject: Re: [PATCH] clocksource: em_sti: Emma Mobile STI driver

On Thu, 3 May 2012, Magnus Damm wrote:
> +/* private flags */
> +#define FLAG_CLOCKEVENT (1 << 0)
> +#define FLAG_CLOCKSOURCE (1 << 1)
> +
> +static int em_sti_start(struct em_sti_priv *p, unsigned long flag)
> +{
> +	int ret = 0;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&p->lock, flags);
> +
> +	if (!(p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
> +		ret = em_sti_enable(p);

That's confusing. You seem to enable both CLOCKEVENT and CLOCKSOURCE
independent of "flag" value.

> +
> +	if (!ret)
> +		p->flags |= flag;

And then just or "flag" ??????

> +	spin_unlock_irqrestore(&p->lock, flags);
> +
> +	return ret;
> +}
> +
> +static void em_sti_stop(struct em_sti_priv *p, unsigned long flag)
> +{
> +	unsigned long flags;
> +	unsigned long f;
> +
> +	spin_lock_irqsave(&p->lock, flags);
> +
> +	f = p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE);
> +	p->flags &= ~flag;
> +
> +	if (f && !(p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
> +		em_sti_disable(p);

Huch? If the caller wants to disable the clockevent, you stop the
clocksource as well because em_sti_disable() stops the clock.

/me is confused.

> +static void em_sti_clock_event_start(struct em_sti_priv *p)
> +{
> +	struct clock_event_device *ced = &p->ced;
> +
> +	em_sti_start(p, FLAG_CLOCKEVENT);
> +
> +	/* TODO: calculate good shift from rate and counter bit width */
> +
> +	ced->shift = 32;
> +	ced->mult = div_sc(p->rate, NSEC_PER_SEC, ced->shift);

IIRC, we have a generic function to do that :)

Thanks,

	tglx
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