Re: [PATCH v7 11/17] ACPI / processor: Make it possible to get CPU hardware ID via GICC

[Hanjun Guo]

On 2015å01æ20æ 19:17, Catalin Marinas wrote:
> On Wed, Jan 14, 2015 at 03:04:59PM +0000, Hanjun Guo wrote:
> > --- a/drivers/acpi/processor_core.c
> > +++ b/drivers/acpi/processor_core.c
> > @@ -64,6 +64,38 @@ static int map_lsapic_id(struct acpi_subtable_header *entry,
> >   	return 0;
> >   }
> >
> > +/*
> > + * On ARM platform, MPIDR value is the hardware ID as apic ID
> > + * on Intel platforms
> > + */
> > +static int map_gicc_mpidr(struct acpi_subtable_header *entry,
> > +		int device_declaration, u32 acpi_id, int *mpidr)
> > +{
> > +	struct acpi_madt_generic_interrupt *gicc =
> > +	    container_of(entry, struct acpi_madt_generic_interrupt, header);
> > +
> > +	if (!(gicc->flags & ACPI_MADT_ENABLED))
> > +		return -ENODEV;
> > +
> > +	/* In the GIC interrupt model, logical processors are
> > +	 * required to have a Processor Device object in the DSDT,
> > +	 * so we should check device_declaration here
> > +	 */
> > +	if (device_declaration && (gicc->uid == acpi_id)) {
> > +		/*
> > +		 * Only bits [0:7] Aff0, bits [8:15] Aff1, bits [16:23] Aff2
> > +		 * and bits [32:39] Aff3 are meaningful, so pack the Affx
> > +		 * fields into a single 32 bit identifier to accommodate the
> > +		 * acpi processor drivers.
> > +		 */
> > +		*mpidr = ((gicc->arm_mpidr & 0xff00000000) >> 8)
> > +			 | gicc->arm_mpidr;
>
> Nitpick: I would clarify the comment here since "meaningful" doesn't
> necessarily mean that the other bits are 0. And if they are not, the
> above masking is not enough. Looking at the ACPI 5.1 spec, bits other
> than Aff[0-3] must be zero.
>
> Same for the pack_mpidr() comment.

OK, how about:

/*
 * bits other than [0:7] Aff0, [8:15] Aff1, [16:23] Aff2 and
 * [32:39] Aff3 must be 0 which is defined in ACPI 5.1, so pack
 * the Affx fields into a single 32 bit identifier to accommodate
 * the acpi processor drivers.
 */

Thanks
Hanjun
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