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SubjectRe: [PATCH v9 05/21] ARM64 / ACPI: Get RSDP and ACPI boot-time tables
On 2015年03月06日 02:51, Lorenzo Pieralisi wrote:
> On Wed, Feb 25, 2015 at 08:39:45AM +0000, Hanjun Guo wrote:
>> From: Al Stone <al.stone@linaro.org>
>>
>> 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/acenv.h for arch specific ACPICA environments and
>> implementation, It is needed unconditionally by ACPI core;
>
> I am not sure we will ever need it since the global lock is not
> needed on HW reduced ACPI (ie ACPI on arm64), and instructions to
> flush the caches are not needed either on arm64.
>
> Anyway, I will have a look if it is worth writing optimized div/shift,
> to give it a purpose to exist.
>
> [...]
>
>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> new file mode 100644
>> index 0000000..8b837ab
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/acpi.h
>> @@ -0,0 +1,45 @@
>> +/*
>> + * Copyright (C) 2013-2014, Linaro Ltd.
>> + * Author: Al Stone <al.stone@linaro.org>
>> + * Author: Graeme Gregory <graeme.gregory@linaro.org>
>> + * Author: Hanjun Guo <hanjun.guo@linaro.org>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation;
>> + */
>> +
>> +#ifndef _ASM_ACPI_H
>> +#define _ASM_ACPI_H
>> +
>> +/* Basic configuration for ACPI */
>> +#ifdef CONFIG_ACPI
>> +#define acpi_strict 1 /* No out-of-spec workarounds on ARM64 */
>> +extern int acpi_disabled;
>> +extern int acpi_noirq;
>> +extern int acpi_pci_disabled;
>> +
>> +static inline void disable_acpi(void)
>> +{
>> + acpi_disabled = 1;
>> + acpi_pci_disabled = 1;
>> + acpi_noirq = 1;
>> +}
>> +
>> +/*
>> + * 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
>> + * obtained from GICC with 0 and not print some error message as well.
>> + * Since MADT must provide at least one GICC structure for GIC
>> + * initialization, CPU will be always available in MADT on ARM64.
>> + */
>> +static inline bool acpi_has_cpu_in_madt(void)
>> +{
>> + return true;
>> +}
>
> I am still trying to make sense of what's this is used for, to me
> it looks like a legacy hack in acpi_processor.c. It is a shame that we need
> to define functions to paper over legacy hacks that make no sense
> whatsoever on arm64.

I'm sorry that I'm confused, why call this as a "hack"? If I remember
correctly, this is a bugfix for x86 from Redhat folks to test kdump
on UP system but without CPU entries in MADT table [1], and we make it
arch independent to introduce acpi_has_cpu_in_madt().

[1]: commit c401eb8ee37, ACPI / processor: Check if LAPIC is present
during initialization

>
>> +static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>
> This is only used on ia64 to pass the _SUN value to arch code to fix up
> the socket id. See above.
>
> You could define last two functions in generic code, and let the
> arch code that needs them override them.
>
> Whether we do it in this series or later, this stuff needs cleaning up.
>
>> +
>> +#endif /* CONFIG_ACPI */
>> +
>> +#endif /*_ASM_ACPI_H*/
>> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
>> index bef04af..218eb7e 100644
>> --- a/arch/arm64/kernel/Makefile
>> +++ b/arch/arm64/kernel/Makefile
>> @@ -34,6 +34,7 @@ arm64-obj-$(CONFIG_KGDB) += kgdb.o
>> arm64-obj-$(CONFIG_EFI) += efi.o efi-stub.o efi-entry.o
>> arm64-obj-$(CONFIG_PCI) += pci.o
>> arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.o
>> +arm64-obj-$(CONFIG_ACPI) += acpi.o
>>
>> obj-y += $(arm64-obj-y) vdso/
>> obj-m += $(arm64-obj-m)
>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>> new file mode 100644
>> index 0000000..f052e7a
>> --- /dev/null
>> +++ b/arch/arm64/kernel/acpi.c
>> @@ -0,0 +1,101 @@
>> +/*
>> + * ARM64 Specific Low-Level ACPI Boot Support
>> + *
>> + * Copyright (C) 2013-2014, Linaro Ltd.
>> + * Author: Al Stone <al.stone@linaro.org>
>> + * Author: Graeme Gregory <graeme.gregory@linaro.org>
>> + * Author: Hanjun Guo <hanjun.guo@linaro.org>
>> + * Author: Tomasz Nowicki <tomasz.nowicki@linaro.org>
>> + * Author: Naresh Bhat <naresh.bhat@linaro.org>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +
>> +#define pr_fmt(fmt) "ACPI: " fmt
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/bootmem.h>
>> +#include <linux/cpumask.h>
>> +#include <linux/init.h>
>> +#include <linux/irq.h>
>> +#include <linux/irqdomain.h>
>> +#include <linux/memblock.h>
>> +#include <linux/smp.h>
>> +
>> +int acpi_noirq; /* skip ACPI IRQ initialization */
>> +int acpi_disabled;
>> +EXPORT_SYMBOL(acpi_disabled);
>> +
>> +int acpi_pci_disabled; /* skip ACPI PCI scan and IRQ initialization */
>> +EXPORT_SYMBOL(acpi_pci_disabled);
>> +
>> +/*
>> + * __acpi_map_table() will be called before page_init(), so early_ioremap()
>> + * or early_memremap() should be called here to for ACPI table mapping.
>> + */
>> +char *__init __acpi_map_table(unsigned long phys, unsigned long size)
>> +{
>> + if (!phys || !size)
>
> Is there a reason to rule out physical address 0x0 ?

No particular reasons, unless some arch/firmware limits, I'm
not sure if we need this check (x86 needs it), I'm CC Leif
to confirm.

Thanks
Hanjun


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