I should warn you that FADT version numbers are notoriously unreliable; In fact, in ACPICA we were eventually forced to abandon them entirely. We use the actual size of the FADT instead.

Bob

-----Original Message-----
From: Hanjun Guo [mailto:hanjun.guo at linaro.org]
Sent: Tuesday, August 19, 2014 5:14 AM
To: Mark Rutland
Cc: Catalin Marinas; Rafael J. Wysocki; graeme.gregory at linaro.org; Arnd
Bergmann; Olof Johansson; grant.likely at linaro.org; Sudeep Holla; Will
Deacon; Jason Cooper; Marc Zyngier; Bjorn Helgaas; Daniel Lezcano; Mark
Brown; Rob Herring; Robert Richter; Zheng, Lv; Moore, Robert; Lorenzo
Pieralisi; Liviu Dudau; Randy Dunlap; Charles Garcia-Tobin; linux-
acpi at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-
kernel at vger.kernel.org; linaro-acpi at lists.linaro.org
Subject: Re: [PATCH v2 05/18] ARM64 / ACPI: Parse FADT table to get PSCI
flags for PSCI init

On 2014-8-19 19:10, Mark Rutland wrote:

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@@ -47,6 +49,26 @@ void __init __acpi_unmap_table(char *map, unsigned

long size)

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 	early_memunmap(map, size);
 }

+static int __init acpi_parse_fadt(struct acpi_table_header *table)
+{
+	struct acpi_table_fadt *fadt = (struct acpi_table_fadt

*)table;

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+
+	/*
+	 * Revision in table header is the FADT Major version,
+	 * and there is a minor version of FADT which was introduced
+	 * by ACPI 5.1, we only deal with ACPI 5.1 or higher version
+	 * to get arm boot flags, or we will disable ACPI.
+	 */
+	if (table->revision < 5 || fadt->minor_revision < 1) {

If we ever get revision 6.0, this would trigger.

Yes, good catch, actually I already fixed that in my local git repo,

+       if (table->revision > 5 ||
+           (table->revision == 5 && fadt->minor_revision >= 1)) {
+               return 0;
+       } else {
+               pr_info("FADT revision is %d.%d, no PSCI support,
+ should be 5.1
or higher\n",
+                       table->revision, fadt->minor_revision);
+               disable_acpi();
+               return -EINVAL;
+       }

Given you return in the first path, you don't need the remaining code
to live in an else block.

Agreed, I will update it, and move disable_acpi() outside this function
and keep it in one place as Sudeep suggested.

Thanks
Hanjun