Re: [PATCH v4 06/18] ARM64 / ACPI: Introduce early_param for "acpi"

Olof Johansson
2014-09-15T06:28:24Z

On Fri, Sep 12, 2014 at 10:00:04PM +0800, Hanjun Guo wrote:
> From: Al Stone <al.stone@linaro.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@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]

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
>