Re: [PATCH v3 13/17] ARM64 / ACPI: Add GICv2 specific ACPI boot support

[Tomasz Nowicki]

On 03.09.2014 20:42, Arnd Bergmann wrote:
> On Monday 01 September 2014 22:57:51 Hanjun Guo wrote:
> > +       /* Collect CPU base addresses */
> > +       count = acpi_parse_entries(sizeof(struct acpi_table_madt),
> > +                                  gic_acpi_parse_madt_cpu, table,
> > +                                  ACPI_MADT_TYPE_GENERIC_INTERRUPT,
> > +                                  ACPI_MAX_GIC_CPU_INTERFACE_ENTRIES);
> > +       if (count < 0) {
> > +               pr_err("Error during GICC entries parsing\n");
> > +               return -EFAULT;
> > +       } else if (!count) {
> > +               /* No GICC entries provided, use address from MADT header */
> > +               struct acpi_table_madt *madt = (struct acpi_table_madt *)table;
> > +
> > +               if (!madt->address)
> > +                       return -EFAULT;
> > +
> > +               cpu_phy_base = (u64)madt->address;
> > +       }
>
> After I read through ACPI-5.1 section 5.2.12.14, I wonder if this is the
> best way to treat a missing ACPI_MADT_TYPE_GENERIC_INTERRUPT table.
>
> Do we expect to see those in practice? It seems like using the x86 local
> APIC address as a fallback for the GIC address is not something we
> should do unless we absolutely have to support a system that doesn't
> have the GIC table.

No, we do not expect and hopefully there will be no such :)

But, we are trying to be as much as possible inline with 5.1 spec, 
5.2.12.14 says:
[...]
If provided here (CPU physical base address), the "Local Interrupt 
Controller Address" field in the MADT must be ignored by the OSPM.
[...]

Regards,
Tomasz



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