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    SubjectRe: [PATCH] kexec: reenable HPET before kexec
    On Thu, 23 Aug 2007 14:38:45 +0530
    Vivek Goyal <vgoyal@in.ibm.com> wrote:
    > Does your kernel 2 boot normally? I mean through BIOS and boot-loader?
    > This explanation seems to be suggesting that because PM and ACPI is
    > disabled, kernel 2 does not search for HPET. If this is the case,
    > this kernel will not boot even through normal boot-loader and will
    > try to use PIT instead?
    >
    > If so, it is not an kexec issue at all.
    >
    > Thanks
    > Vivek

    kernel 2 boots normally through BIOS and boot-loader. I agree with your
    explanation.
    It seems that kernel 2 can't enable PIT, when it is executed by kexec.
    As kernel 1 disabled HPET(IRQ0 source) and PIT is "broken"(or isn't
    enabled) IRQ0 are not triggered at all, and kernel 2 hangs.
    As kernel 2 boots normally through BIOS and boot-loader, than
    additional code needed(in Linux kernel init code) for PIT or ACPI
    or APIC initialization, I mean the same code as executed on BIOS stage.
    I agree that it's not an kexec issue. But can we use my fix as a
    workaround(to make kexec work) until PIT will be fixed?
    Everything above is correct for i386/x86_64 RT(2.6.23-rc2-rt2) kernel
    and for i368 "plain"(2.6.23-rc3) kernel. Bug isn't reproduced in 2.6.23-rc3
    x86_64 kernel, because x86_64 code never disables HPET. So on every
    boot(initiated by kexec or BIOS) IRQ0 are triggered.

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