acpi/arm64: ignore 5.1 FADTs that are reported as 5.0

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>
aarch64-laptops · Jun 17, 2019 · a7edc17 · a7edc17
1 parent f9b3d76
commit a7edc17
Showing 1 changed file with 7 additions and 3 deletions.
diff --git 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");
 	}
 
 	if (!(fadt->flags & ACPI_FADT_HW_REDUCED)) {