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

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Date:	Tue, 9 Sep 2014 17:26:49 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	"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 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).

> 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.

-- 
Catalin

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