Date:	Tue, 19 Aug 2014 17:35:41 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Sudeep Holla <sudeep.holla@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>
CC:	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Lv Zheng <lv.zheng@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Al Stone <al.stone@...aro.org>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>
Subject: Re: [PATCH v2 02/18] ARM64 / ACPI: Get RSDP and ACPI boot-time tables

On 2014-8-19 2:30, Sudeep Holla wrote:
> On 04/08/14 16:28, Hanjun Guo wrote:
>> From: Al Stone <al.stone@...aro.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/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;
> 
> This can go away now, as it's already present in v3.17-rc1

Thanks for the reminding, I will rebase this patch set on top of
3.17-rc1 and remove the outdated description.

> 
>>    - asm/acenv.h for arch specific ACPICA environments and
>>      implementation;
>>    - asm/acpi.h for arch specific variables and functions needed by
>>      ACPI driver core;
>>    - acpi.c for ARM64 related ACPI implementation for ACPI driver
>>      core;
>>
>> acpi_boot_table_init() is introduced to get RSDP and boot-time tables,
>> it will be called in setup_arch() before paging_init(), so we should
>> use eary_memremap() mechanism here to get the RSDP and all the table
>> pointers.
[...]
>> +
>> +/*
>> + * Checking for the posibility that the CPU can be initialized from the MADT.
>> + * It's used from ACPI core in crash kernel case where boot CPU is not
>> + * necessarily CPU0 like spec demands. Since MADT must provide at least one
> 
> Do you mean ACPI spec demands CPU0 to be boot cpu ?

ACPI spec demands CPU0 (BSP) should be the first entry in MADT.

> 
> IIUC it's basically to handle UP system with SMP kernel. IWO if all the
> ACPI resources are reused from SMP system to boot UP system with SMP
> kernel, with this check the ACPI core won't override the CPU index
> obtained from GIC/APIC mapping to zero.

Yes, you are right, I will update the comments.

> 
>> + * GICC structure for GIC initialization, CPU will be always available in
>> + * MADT on ARM64.
>> + */
>> +static inline bool acpi_has_cpu_in_madt(void)
>> +{
>> +    return 1;
> 
> probably true instead of 1

ok.

> 
>> +}
>> +
>> +static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>> +
>> +#endif /* CONFIG_ACPI */
>> +
>> +#endif /*_ASM_ACPI_H*/
>> diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
>> new file mode 100644
>> index 0000000..cee7d3f
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/cpu.h
>> @@ -0,0 +1,11 @@
>> +/*
>> + *  Copyright (C) 2013-2014 ARM Ltd.
>> + *
>> + * 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_CPU_H
>> +#define __ASM_CPU_H
>> +
>> +#endif
>> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
>> index cdaedad..b568c26 100644
>> --- a/arch/arm64/kernel/Makefile
>> +++ b/arch/arm64/kernel/Makefile
>> @@ -29,6 +29,7 @@ arm64-obj-$(CONFIG_ARM64_CPU_SUSPEND)    += sleep.o suspend.o
>>   arm64-obj-$(CONFIG_JUMP_LABEL)        += jump_label.o
>>   arm64-obj-$(CONFIG_KGDB)        += kgdb.o
>>   arm64-obj-$(CONFIG_EFI)            += efi.o efi-stub.o efi-entry.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..395778c
>> --- /dev/null
>> +++ b/arch/arm64/kernel/acpi.c
>> @@ -0,0 +1,69 @@
>> +/*
>> + *  ARM64 Specific Low-Level ACPI Boot Support
>> + *
>> + *  Copyright (C) 2013-2014, Linaro Ltd.
>> + *    Author: Al Stone <al.stone@...aro.org>
>> + *    Author: Graeme Gregory <graeme.gregory@...aro.org>
>> + *    Author: Hanjun Guo <hanjun.guo@...aro.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.
>> + */
>> +
>> +#include <linux/init.h>
>> +#include <linux/acpi.h>
>> +#include <linux/cpumask.h>
>> +#include <linux/memblock.h>
>> +#include <linux/irq.h>
>> +#include <linux/irqdomain.h>
>> +#include <linux/bootmem.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)
>> +        return NULL;
>> +
>> +    return early_memremap(phys, size);
>> +}
>> +
>> +void __init __acpi_unmap_table(char *map, unsigned long size)
>> +{
>> +    if (!map || !size)
>> +        return;
>> +
>> +    early_memunmap(map, size);
>> +}
>> +
>> +/*
>> + * 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.

> 
>> +        disable_acpi();
>> +        return;
>> +    }
>> +}
>> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
>> index fc50461..85c6326 100644
>> --- a/arch/arm64/kernel/setup.c
>> +++ b/arch/arm64/kernel/setup.c
>> @@ -43,6 +43,7 @@
>>   #include <linux/of_fdt.h>
>>   #include <linux/of_platform.h>
>>   #include <linux/efi.h>
>> +#include <linux/acpi.h>
>>
>>   #include <asm/fixmap.h>
>>   #include <asm/cputype.h>
>> @@ -385,6 +386,9 @@ void __init setup_arch(char **cmdline_p)
>>       efi_init();
>>       arm64_memblock_init();
>>
>> +    /* Parse the ACPI tables for possible boot-time configuration */
>> +    acpi_boot_table_init();
>> +
>>       paging_init();
>>       request_standard_resources();

Thanks
Hanjun

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