Re: [PATCH] clocksource: em_sti: Emma Mobile STI driver
From: Magnus Damm
Date: Tue May 08 2012 - 13:06:31 EST
Hi Thomas,
On Tue, May 8, 2012 at 4:10 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> 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.
Hm, I believe the idea is to check if it has been enabled already...
>> +
>> + if (!ret)
>> + p->flags |= flag;
>
> And then just or "flag" ??????
... but it certainly is overly complicated. I'll rework it into
something that is easier to digest. =)
>> + 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.
I believe the idea is that if the timer is currently enabled (f) and
if we are the last user thenthen stop.
A regular usage counter probably makes much more sense!
>> +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 :)
Ok, thanks for pointing that out. Need to look it up!
Will update and post a V2. Thanks for your help!
Cheers,
/ magnus
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