linux-kernel - Re: [PATCH v3 02/17] ARM64 / ACPI: Get RSDP and ACPI boot-time tables

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Date:	Wed, 10 Sep 2014 15:30:19 +0800
From:	Hanjun Guo <guohanjun@...wei.com>
To:	Catalin Marinas <catalin.marinas@....com>,
	"hanjun.guo@...aro.org" <hanjun.guo@...aro.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>,
	Olof Johansson <olof@...om.net>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Sudeep Holla <Sudeep.Holla@....com>,
	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 v3 02/17] ARM64 / ACPI: Get RSDP and ACPI boot-time tables

On 2014/9/10 0:26, Catalin Marinas wrote:
> On Mon, Sep 01, 2014 at 03:57:40PM +0100, Hanjun Guo wrote:
>> diff --git a/arch/arm64/include/asm/acenv.h b/arch/arm64/include/asm/acenv.h
>> new file mode 100644
>> index 0000000..3899ee6
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/acenv.h
>> @@ -0,0 +1,18 @@
>> +/*
>> + * ARM64 specific ACPICA environments and implementation
>> + *
>> + * Copyright (C) 2014, Linaro Ltd.
>> + *   Author: Hanjun Guo <hanjun.guo@...aro.org>
>> + *   Author: Graeme Gregory <graeme.gregory@...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.
>> + */
>> +
>> +#ifndef _ASM_ACENV_H
>> +#define _ASM_ACENV_H
>> +
>> +#define ACPI_FLUSH_CPU_CACHE() WARN_ONCE(1, "Not currently supported on ARM64")
> 
> Does this mean that it will be supported at some point? Looking at the
> places where this function is called, I don't really see how this would
> ever work on ARM. Which means that we add such macro just to be able to
> compile code that would never be used on arm64. I would rather see the
> relevant ACPI files only compiled on x86/IA-64 rather than arm64.
> 
>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>> new file mode 100644
>> index 0000000..9252f72
>> --- /dev/null
>> +++ b/arch/arm64/kernel/acpi.c
> 
> [...]
> 
>> +/*
>> + * 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 MADT after
>> + * this function is called.
>> + */
>> +void __init acpi_boot_table_init(void)
>> +{
>> +	/* If acpi_disabled, bail out */
>> +	if (acpi_disabled)
>> +		return;
> 
> So at this point, there wouldn't be anything yet to set acpi_disabled to
> 1, unless !CONFIG_ACPI.
> 
>> +
>> +	/* Initialize the ACPI boot-time table parser. */
>> +	if (acpi_table_init())
>> +		disable_acpi();
> 
> Do you need anything more to add to this function later? Otherwise, just
> call it in setup_arch() directly (maybe dependent on
> IS_ENABLED(CONFIG_ACPI) or just create an equivalent dummy
> acpi_table_init() when not configured).

We add FADT parse function to this function later.

> 
>> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
>> index c96172a..fb7cc0e 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/cpu.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();
> 
> Is there any dummy acpi_boot_table_init() when !CONFIG_ACPI? I couldn't
> see one in this patch, so I don't see how this would compile when ACPI
> is disabled.

There is a stub function in linux/acpi.h when ACPI is disabled.

Thanks
Hanjun


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