Re: [patch 08/18] PS3: Kexec support

[Michael Ellerman <michael@ellerman.id.au>]

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On Wed, 2007-06-06 at 14:55 -0700, Geoff Levand wrote:
> Michael Ellerman wrote:
> >> --- a/arch/powerpc/platforms/ps3/htab.c
> >> +++ b/arch/powerpc/platforms/ps3/htab.c
> >> @@ -234,10 +234,18 @@ static void ps3_hpte_invalidate(unsigned
> >>  
> >>  static void ps3_hpte_clear(void)
> >>  {
> >> -	/* Make sure to clean up the frame buffer device first */
> >> -	ps3fb_cleanup();
> >> +	int result;
> >>  
> >> -	lv1_unmap_htab(htab_addr);
> >> +	DBG(" -> %s:%d\n", __func__, __LINE__);
> >> +
> >> +	result = lv1_unmap_htab(htab_addr);
> >> +	BUG_ON(result);
> >> +
> >> +	ps3_mm_shutdown();
> >> +
> >> +	ps3_mm_vas_destroy();
> >> +
> >> +	DBG(" <- %s:%d\n", __func__, __LINE__);
> >>  }
> > 
> > Do you really want to be calling DBG() here? Hmm, it looks like it
> > doesn't actually do anything?
> 
> 
> Sure, it uses udbg_printf, and works OK.

Which is hooked up to what?

> >> +static void ps3_chip_mask(unsigned int virq)
> >> +{
> >> +	struct ps3_private *pd = get_irq_chip_data(virq);
> >> +	u64 bit = 0x8000000000000000UL >> virq;
> >> +	u64 *p = &pd->bmp.mask;
> >> +	u64 old;
> >> +	unsigned long flags;
> >> +
> >> +	pr_debug("%s:%d: cpu %u, virq %d\n", __func__, __LINE__, pd->cpu, virq);
> >> +
> >> +	local_irq_save(flags);
> >> +	asm volatile(
> >> +		     "1:	ldarx %0,0,%3\n"
> >> +		     "andc	%0,%0,%2\n"
> >> +		     "stdcx.	%0,0,%3\n"
> >> +		     "bne-	1b"
> >> +		     : "=&r" (old), "+m" (*p)
> >> +		     : "r" (bit), "r" (p)
> >> +		     : "cc" );
> >> +
> >> +	lv1_did_update_interrupt_mask(pd->node, pd->cpu);
> >> +	local_irq_restore(flags);
> > 
> > How is this different from set_bit() ?  (asm-powerpc/bitops.h)
> > 
> > ps. now that I see you're just moving this code around someone's
> > probably already asked that question.
> 
> 
> This was contributed by Ben H as the fastest way.  I think the
> reason was that we could minimize the time between local_irq_save
> and local_irq_restore?

To save ~10 instructions? Followed by a HV call? I guess Ben has some
really good benchmark data to support it ;)

cheers


-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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