linux-kernel - Re: [PATCH 10/13] Do not try to disable hpet if it hasn't been initialized before

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Date:	Thu, 08 Jul 2010 18:05:37 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	stefano@...bellini.net, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xensource.com, Stefano.Stabellini@...citrix.com,
	sheng@...ux.intel.com, ddutile@...hat.com, jeremy@...p.org
Subject: Re: [PATCH 10/13] Do not try to disable hpet if it hasn't been
 initialized before

On Wed, 2010-06-30 at 13:53 -0400, Konrad Rzeszutek Wilk wrote:
> On Mon, Jun 21, 2010 at 05:14:04PM +0100, stefano@...bellini.net wrote:
> > From: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > 
> > hpet_disable is called unconditionally on machine reboot if hpet support
> > is compiled in the kernel.
> > hpet_disable only checks if the machine is hpet capable but doesn't make
> > sure that hpet has been initialized.
> 
> CC-ing John Stultz who has had his head wrapped around this time-thingy.
> 
> Hi John!
> 
> What are your thoughts about this patch?

Sorry for the slow reply.

The patch looks good to me. It makes the code easier to read as well!

However, I've not had my head in the hpet details for awhile, so
Venkatesh's ack (already provided) is the better endorsement.

thanks
-john


> > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > ---
> >  arch/x86/kernel/hpet.c |   18 ++++++++++--------
> >  1 files changed, 10 insertions(+), 8 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
> > index 23b4ecd..2b299da 100644
> > --- a/arch/x86/kernel/hpet.c
> > +++ b/arch/x86/kernel/hpet.c
> > @@ -959,16 +959,18 @@ fs_initcall(hpet_late_init);
> >  
> >  void hpet_disable(void)
> >  {
> > -	if (is_hpet_capable()) {
> > -		unsigned int cfg = hpet_readl(HPET_CFG);
> > +	unsigned int cfg;
> >  
> > -		if (hpet_legacy_int_enabled) {
> > -			cfg &= ~HPET_CFG_LEGACY;
> > -			hpet_legacy_int_enabled = 0;
> > -		}
> > -		cfg &= ~HPET_CFG_ENABLE;
> > -		hpet_writel(cfg, HPET_CFG);
> > +	if (!is_hpet_capable() || !hpet_address || !hpet_virt_address)
> > +		return;
> > +
> > +	cfg = hpet_readl(HPET_CFG);
> > +	if (hpet_legacy_int_enabled) {
> > +		cfg &= ~HPET_CFG_LEGACY;
> > +		hpet_legacy_int_enabled = 0;
> >  	}
> > +	cfg &= ~HPET_CFG_ENABLE;
> > +	hpet_writel(cfg, HPET_CFG);
> >  }
> >  
> >  #ifdef CONFIG_HPET_EMULATE_RTC
> > -- 
> > 1.7.0.4
> > 
> > --
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