Re: [PATCH 1/3] ia64: convert to use clocksource code

[Peter Keilty <peter.keilty@hp.com>]

Daniel Walker wrote:

> On Thu, 2007-04-26 at 16:26 -0400, Peter Keilty wrote:
>
>  
>
> > +        .mask           = (1LL << 40) - 1,
> > +        .mult           = 0, /*to be caluclated*/
> > +        .shift          = 16,
> > +        .is_continuous  = 1,
> > };
> >    
>
> You should use CLOCKSOURCE_MASK() here ..
>
>  
It is correct in patch 3, I believe.

>  
>
> > diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
> > index daa4940..a20b4d6 100644
> > --- a/include/linux/clocksource.h
> > +++ b/include/linux/clocksource.h
> > @@ -61,6 +61,9 @@ struct clocksource {
> > 	u32 shift;
> > 	unsigned long flags;
> > 	cycle_t (*vread)(void);
> > +#ifdef CONFIG_IA64
> > +	void *fsys_mmio_ptr;	/* used by fsyscall asm code */
> > +#endif
> >    
>
> Could you explain in detail why this is needed?
>  
This ptr is needed to hold the mmio address to read the cycle value.
The fast ia64 path utilizies a special gate page which can allow user
code to execute small amount of kernel code, normal calling a function
not done and so the address is need. The fast syscall path executes on
user stack, between user/kernel state. And if the the fast path has to 
fallback
to the slow syscall code the vread will be needed and used.
Hope this helps.

> Daniel
>
>  
-
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