linux-kernel - Re: [PATCH v4 06/18] ARM64 / ACPI: Introduce early

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Message-ID: <20140915062824.GB26649@localhost>
Date:	Sun, 14 Sep 2014 23:28:24 -0700
From:	Olof Johansson <olof@...om.net>
To:	Hanjun Guo <hanjun.guo@...aro.org>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <mark.rutland@....com>,
	Grant Likely <grant.likely@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Jon Masters <jcm@...hat.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@....com, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linaro-acpi@...ts.linaro.org, Al Stone <al.stone@...aro.org>
Subject: Re: [PATCH v4 06/18] ARM64 / ACPI: Introduce early_param for "acpi"

On Fri, Sep 12, 2014 at 10:00:04PM +0800, Hanjun Guo wrote:
> From: Al Stone <al.stone@...aro.org>
> 
> Introduce one early parameters "off" for "acpi" to disable ACPI on
> ARM64.
> 
> This ensures the kernel uses the DT on a platform that provides both
> ACPI tables and DT.
> 
> Signed-off-by: Al Stone <al.stone@...aro.org>
> Signed-off-by: Graeme Gregory <graeme.gregory@...aro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> ---
>  Documentation/kernel-parameters.txt |    3 ++-
>  arch/arm64/kernel/acpi.c            |   15 +++++++++++++++
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 5ae8608..9dfb1d8 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -165,7 +165,7 @@ multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
>  bytes respectively. Such letter suffixes can also be entirely omitted.
>  
>  
> -	acpi=		[HW,ACPI,X86]
> +	acpi=		[HW,ACPI,X86,ARM]

ARM64, not ARM.

>  			Advanced Configuration and Power Interface
>  			Format: { force | off | strict | noirq | rsdt }
>  			force -- enable ACPI if default was off
> @@ -175,6 +175,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  				strictly ACPI specification compliant.
>  			rsdt -- prefer RSDT over (default) XSDT
>  			copy_dsdt -- copy DSDT to memory
> +			For ARM64, ONLY "acpi=off" is available.

Both force and off should be made available, since they're the two main switches here.

>  			See also Documentation/power/runtime_pm.txt, pci=noacpi
>  
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index 9252f72..693da7f 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -67,3 +67,18 @@ void __init acpi_boot_table_init(void)
>  	if (acpi_table_init())
>  		disable_acpi();
>  }
> +
> +static int __init parse_acpi(char *arg)
> +{
> +	if (!arg)
> +		return -EINVAL;
> +
> +	/* "acpi=off" disables both ACPI table parsing and interpreter */
> +	if (strcmp(arg, "off") == 0)
> +		disable_acpi();
> +	else
> +		return -EINVAL;	/* Core will print when we return error */

For symmetry, you should handle acpi=force here too (i.e. if someone
disables by default, which I expect we'll ask for when this code is
first merged).

> +
> +	return 0;
> +}
> +early_param("acpi", parse_acpi);
> -- 
> 1.7.9.5
> 
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