Re: [PATCH v4 12/18] ACPI / processor: Make it possible to get CPU hardware ID via GICC

Hanjun Guo
2014-09-16T00:11:59Z

On 2014年09月15日 15:05, Olof Johansson wrote:
> On Fri, Sep 12, 2014 at 10:00:10PM +0800, Hanjun Guo wrote:
>> Introduce a new function map_gicc_mpidr() to allow MPIDRs to be obtained
>> from the GICC Structure introduced by ACPI 5.1.
>>
>> MPIDR is the CPU hardware ID as local APIC ID on x86 platform, so we use
>> MPIDR not the GIC CPU interface ID to identify CPUs.
>>
>> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
>> ---
>> arch/arm64/include/asm/acpi.h | 32 ++++++++++++++++++++++++++++++++
>> arch/arm64/kernel/acpi.c | 1 -
>> drivers/acpi/processor_core.c | 37 +++++++++++++++++++++++++++++++++++++
>> 3 files changed, 69 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> index da8f74a..2c48f70e 100644
>> --- a/arch/arm64/include/asm/acpi.h
>> +++ b/arch/arm64/include/asm/acpi.h
>> @@ -12,6 +12,8 @@
>> #ifndef _ASM_ACPI_H
>> #define _ASM_ACPI_H
>>
>> +#include <asm/smp_plat.h>
>> +
>> /* Basic configuration for ACPI */
>> #ifdef CONFIG_ACPI
>> #define acpi_strict 1 /* No out-of-spec workarounds on ARM64 */
>> @@ -38,6 +40,36 @@ static inline void disable_acpi(void)
>> acpi_noirq = 1;
>> }
>>
>> +/* MPIDR value provided in GICC structure is 64 bits, but
>> + * the acpi processor driver use the 32 bits cpu hardware
>> + * ID (apic_id on intel platform) everywhere, it is pretty
>> + * hard to modify the acpi processor driver to accept the
>> + * 64 bits MPIDR value, at the same time, only 32 bits of
>> + * the MPIDR is used in the 64 bits MPIDR, just pack the
>> + * Affx fields into a single 32 bit identifier to accommodate
>> + * the acpi processor drivers.
>> + */
> This is a pretty run-on comment.
>
> I'd much rather value something like:
>
> Existing apic_id is 32-bit, to conform to the same datatype we need to repack the GICC
> structure MPIDR.
>
> The two formats are:
>
> <show how the 64-bit format is laid out>
> <show how the 32-bit format is laid out>
>
>
>> +static inline u32 pack_mpidr_into_32_bits(u64 mpidr)
> That's a pretty long name for an exported function.
>
>> +{
>> + /*
>> + * Bits [0:7] Aff0;
>> + * Bits [8:15] Aff1;
>> + * Bits [16:23] Aff2;
>> + * Bits [32:39] Aff3;
>> + */
> With the format description above added, then this comment can be removed.

ok, I will update it.

>
>> + return (u32) ((mpidr & 0xff00000000) >> 8) | mpidr;
>> +}
>> +
>> +/*
>> + * The ACPI processor driver for ACPI core code needs this macro
>> + * to find out this cpu was already mapped (mapping from CPU hardware
>> + * ID to CPU logical ID) or not.
>> + *
>> + * cpu_logical_map(cpu) is the mapping of MPIDR and the logical cpu,
>> + * and MPIDR is the cpu hardware ID we needed to pack.
>> + */
>> +#define cpu_physical_id(cpu) pack_mpidr_into_32_bits(cpu_logical_map(cpu))
>> +
>> /*
>> * It's used from ACPI core in kdump to boot UP system with SMP kernel,
>> * with this check the ACPI core will not override the CPU index
>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>> index 644b8b8..2ef8721 100644
>> --- a/arch/arm64/kernel/acpi.c
>> +++ b/arch/arm64/kernel/acpi.c
>> @@ -24,7 +24,6 @@
>> #include <linux/bootmem.h>
>> #include <linux/smp.h>
>>
>> -#include <asm/smp_plat.h>
>> #include <asm/cputype.h>
>> #include <asm/cpu_ops.h>
>>
>> diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
>> index e32321c..4007313 100644
>> --- 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.
>> + */
> Here's duplicated information again. Reusing the same macro as in the header file
> would help overall readability, I think.

The problem is that it will cause compile error on x86 and ia64 platform,
it is ARM64 specific only.

>
>> + *mpidr = ((gicc->arm_mpidr & 0xff00000000) >> 8)
>> + | gicc->arm_mpidr;
>> + return 0;
>> + }
>> +
>> + return -EINVAL;
>> +}
>> +

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