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SubjectRe: [PATCH] x86: Bypass legacy PIC and PIT on ACPI hardware reduced platform

* Li, Aubrey <aubrey.li@linux.intel.com> wrote:

> >> - in x86_reduced_hw_init() set 'legacy_pic' to 'null_legacy_pic'
> >>
> >> - clean up 'global_clock_event' handling: instead of a global
> >> variable, move its management into x86_platform_ops::get_clockevent()
> >> and set the method to hpet/pit/abp/etc. specific handlers that
> >> return the right clockevent device.
> >>
> >> - in your x86_reduced_hw_init() function add the hpet clockevent
> >> device to x86_platform_ops::get_clockevent, overriding the default
> >> PIT.
>
> how about this one?
>
> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> index b9e30da..70955d6 100644
> --- a/arch/x86/kernel/acpi/boot.c
> +++ b/arch/x86/kernel/acpi/boot.c
> @@ -1541,6 +1541,16 @@ int __init early_acpi_boot_init(void)
> */
> early_acpi_process_madt();
>
> + /*
> + * Override x86_init functions and bypass legacy pic
> + * in hardware-reduced ACPI mode
> + */
> + if (acpi_gbl_reduced_hardware) {
> + x86_init.timers.timer_init = x86_init_noop;
> + x86_init.irqs.pre_vector_init = x86_init_noop;
> + legacy_pic = &null_legacy_pic;
> + }

Sounds good to me, assuming it builds, boots and works! :-)

A couple of extra suggestions:

1)

I'd suggest moving it into its own dedicated, appropriately named
static function, to make it clear that 'ACPI Reduced Hardware' init
happens there.

2)

I'd also initialize it like this:

x86_init.timers.timer_init = x86_init_noop;
x86_init.irqs.pre_vector_init = x86_init_noop;
legacy_pic = &null_legacy_pic;

to make the noop patterns stand out better.

3)

Once all is said and done, please also make acpi_gbl_reduced_hardware
a flag internal to the ACPI code, not exposed to and used by other
bits of x86 code.

> If the above makes sense, I'll send poweroff and reboot change
> together in a seperate patch.

Yeah, please send them in a single series though, so they form a
logical group.

Thanks,

Ingo


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