Re: [PATCH v2 02/18] ARM64 / ACPI: Get RSDP and ACPI boot-time tables

[Sudeep Holla]

On 19/08/14 10:35, Hanjun Guo wrote:
> On 2014-8-19 2:30, Sudeep Holla wrote:
> > On 04/08/14 16:28, Hanjun Guo wrote:
> > > From: Al Stone <al.stone@xxxxxxxxxx>
> > >
> > > As we want to get ACPI tables to parse and then use the information
> > > for system initialization, we should get the RSDP (Root System
> > > Description Pointer) first, it then locates Extended Root Description
> > > Table (XSDT) which contains all the 64-bit physical address that
> > > pointer to other boot-time tables.
> > >
> > > Introduce acpi.c and its related head file in this patch to provide
> > > fundamental needs of extern variables and functions for ACPI core,
> > > and then get boot-time tables as needed.
> > >     - asm/cpu.h need for ACPI core and will be updated in the future to
> > >       add definitions for arch_(un)register_cpu which are required for
> > >       ACPI based physical CPU hotplug;

[...]

> > > +/*
> > > + * acpi_boot_table_init() called from setup_arch(), always.
> > > + *    1. find RSDP and get its address, and then find XSDT
> > > + *    2. extract all tables and checksums them all
> > > + *
> > > + * We can parse ACPI boot-time tables such as FADT, MADT after
> > > + * this function is called.
> > > + */
> > > +void __init acpi_boot_table_init(void)
> > > +{
> > > +    /* If acpi_disabled, bail out */
> > > +    if (acpi_disabled)
> > > +        return;
> > > +
> > > +    /* Initialize the ACPI boot-time table parser. */
> > > +    if (acpi_table_init()) {
> >
> > Can't we call acpi_table_init directly in setup ?
> > IIUC x86 has acpi_boot_table_init as it parses Boot Flags
> > table(ACPI_SIG_BOOT)
>
> Yes, we can. But I think it not a big deal to dot that, if that
> makes the code more readable, I will update it.

I agree, but I actually wanted to check if we ever have to use/parse
Simple Boot Flag Table on ARM64 which is reserved but not part of ACPI
spec. I assume x86 use either for Legacy reason or firmware expects it.

Regards,
Sudeep

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