Re: [RFC PATCH] acpi/arm64: ignore 5.1 FADTs that are reported as 5.0

[Lee Jones <lee.jones@linaro.org>]

On Wed, 19 Jun 2019, Ard Biesheuvel wrote:

> Some Qualcomm Snapdragon based laptops built to run Microsoft Windows
> are clearly ACPI 5.1 based, given that that is the first ACPI revision
> that supports ARM, and introduced the FADT 'arm_boot_flags' field,
> which has a non-zero field on those systems.
> 
> So in these cases, infer from the ARM boot flags that the FADT must be
> 5.1 or later, and treat it as 5.1.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  arch/arm64/kernel/acpi.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index 803f0494dd3e..7722e85fb69c 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -155,10 +155,14 @@ static int __init acpi_fadt_sanity_check(void)
>  	 */
>  	if (table->revision < 5 ||
>  	   (table->revision == 5 && fadt->minor_revision < 1)) {
> -		pr_err("Unsupported FADT revision %d.%d, should be 5.1+\n",
> +		pr_err(FW_BUG "Unsupported FADT revision %d.%d, should be 5.1+\n",
>  		       table->revision, fadt->minor_revision);
> -		ret = -EINVAL;
> -		goto out;
> +
> +		if (!fadt->arm_boot_flags) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +		pr_err("FADT has ARM boot flags set, assuming 5.1\n");

Tested-by: Lee Jones <lee.jones@linaro.org>

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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