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