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

Maxim Levitsky
2007-03-29T16:51:36Z

On Thursday 29 March 2007 18:35:21 Linus Torvalds wrote:
>
> 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
>

Hi,
I agree, and as you said I did exactly that:

out_nohpet:
iounmap(hpet_virt_address);
hpet_virt_address = NULL;
boot_hpet_disable = 1; <<<--- this ensures that is_hpet_capable() will never return positive value

I also sent an updated version on my patch with subject line "[PATCH v2] Add suspend/resume for HPET"

I forgot (a typo) to check error code in hpet_register_sysfs
Thanks to Sergei Shtylyov for pointing me on that.

This patch should be ok.

Best regards,
Maxim Levitsky