Re: setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms

[Thomas Gleixner]

On Thu, 1 Aug 2019, Daniel Drake wrote:
> On Thu, Aug 1, 2019 at 3:16 PM Aubrey Li <aubrey.intel@xxxxxxxxx> wrote:
> However, the only way this can be called is from hpet_enable().
> 
> hpet_enable() is called from 2 places:
>  1. From hpet_time_init(). This is the default x86 timer_init that
> acpi_generic_reduced_hw_init() took out of action here.
>  2. From hpet_late_init(). However that function is only called late,
> after calibrate_APIC_clock() has already crashed the kernel. Also,
> even if moved earlier it would also not call hpet_enable() here
> because the ACPI HPET table parsing has already populated
> hpet_address.
> 
> I tried slotting in a call to hpet_enable() at an earlier point
> regardless, but I still end up with the kernel hanging later during
> boot, probably because irq0 fails to be setup and this error is hit:
>     if (setup_irq(0, &irq0))
>         pr_info("Failed to register legacy timer interrupt\n");

Right. The thing also lacks PIT :)

So there are two options:

   1) Make sure the HPET is parsed somehow even with the reduced stuff

   2) Make the clock frequency detection work.

#1 is a trainwreck

#2 is something we really want to have anyway. See the other reply. I cc'ed
   Tom there, he should be able to give us the missing link.

Thanks,

	tglx