Re: [PATCH v3 04/17] ARM64 / ACPI: Introduce early_param for "acpi"

Bjorn Helgaas
2014-09-09T17:17:00Z

On Mon, Sep 1, 2014 at 8:57 AM, Hanjun Guo <hanjun.guo@linaro.org> wrote:
> From: Al Stone <al.stone@linaro.org>
>
> Introduce one early parameters "off" for "acpi" to disable ACPI on
> ARM64.

It might be worth mentioning the purpose of this in the changelog (and
maybe the documentation). I don't think this parameter is supported
on ia64, and on x86 it seems like it's mostly used as a "fix" by
Ubuntu users who consider the problem resolved when they find this
parameter. That just means we don't get a chance to fix the real
underlying problem, so I'm not sure it's a real benefit to have the
parameter.

> Signed-off-by: Al Stone <al.stone@linaro.org>
> Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.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]
> 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.
>
> See also Documentation/power/runtime_pm.txt, pci=noacpi
>
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index b6940a0..9547275 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -74,3 +74,18 @@ void __init acpi_boot_table_init(void)
> * TBD when ARM/ARM64 starts to support suspend...
> */
> int (*acpi_suspend_lowlevel)(void) = NULL;
> +
> +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 */
> +
> + return 0;
> +}
> +early_param("acpi", parse_acpi);
> --
> 1.7.9.5
>