Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver

[Kumar Gala <galak@kernel.crashing.org>]

On May 17, 2007, at 1:07 PM, Sergei Shtylyov wrote:

> Hello.
>
> Kumar Gala wrote:
>
> > > Index: linux-2.6/arch/powerpc/kernel/time.c
> > > ===================================================================
> > > --- linux-2.6.orig/arch/powerpc/kernel/time.c
> > > +++ linux-2.6/arch/powerpc/kernel/time.c
> [...]
> > > @@ -128,6 +129,83 @@ unsigned long ppc_tb_freq;
> > >  static u64 tb_last_jiffy __cacheline_aligned_in_smp;
> > >  static DEFINE_PER_CPU(u64, last_jiffy);
> > >
> > > +#ifdef CONFIG_GENERIC_CLOCKEVENTS
> > > +
> > > +#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
> > > +#define DECREMENTER_MAX 0xffffffff
> > > +#else
> > > +#define DECREMENTER_MAX 0x7fffffff /* setting MSB triggers an   
> > > interrupt */
> > > +#endif
> > > +
> > > +static int decrementer_set_next_event(unsigned long evt,
> > > +                      struct clock_event_device *dev)
> > > +{
> > > +#if defined(CONFIG_40x)
> > > +    mtspr(SPRN_PIT, evt);    /* 40x has a hidden PIT auto- 
> > > reload  register */
> > > +#elif defined(CONFIG_BOOKE)
> > > +    mtspr(SPRN_DECAR, evt); /* Book E has  separate auto-reload   
> > > register */
> > > +    set_dec(evt);
>
> > what's the point of setting decar if you're just going to set_dec  
> > as  well?
>
>    Bothered to read the Book E specs? ;-)

I have :)

>    Loading DECAR doesn't auto-reload DEC. What I want is both set  
> the auto-reload value and start counting down from it at the same  
> time (if the decrementer is in auto-reload mode).

I see you're using DECAR to make it periodic.

> [big cut-off]
>
> WBR, Sergei

I haven't looked at all the new clock/timer code, is there any  
utility in having support for more than one clock source?

- k
-
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