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


    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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