Re: [ PATCH] Add suspend/resume for HPET was: Re: [3/6] 2.6.21-rc4:known regressions

[Linus Torvalds]

On Thu, 29 Mar 2007, Maxim wrote:

> On Thursday 29 March 2007 07:08:58 Linus Torvalds wrote:
> > 
> > (Or, better yet, shouldn't we set "boot_hpet_disable" when we decide not 
> > to use the HPET, and set hpet_virt_address to NULL?)
> 
> This is done here
> 
> out_nohpet:
> 	iounmap(hpet_virt_address);
> 	hpet_virt_address = NULL;

No, that only clears hpet_virt_address, and thus makes all subsequent 
"hpet_readl()" and "hpet_writel()" calls oops.

But it doesn't actually *tell* anybody that the HPET is disabled, so if 
you later on do

	if (is_hpet_capable()) {
		time = hpet_readl(..);
		..

you will just Oops!

So as far as I can see, even with your latest patch, if hpet_enable() 
fails (and triggers the "goto out_nohpet" cases), you'll just oops 
immediately when you try to suspend/resume the HPET.

THAT was what I meant - when we clear hpet_virt_address, we should also 
tell all potential subsequent users that the HPET is not there!

		Linus
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