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    SubjectRE: [PATCH v2 05/18] ARM64 / ACPI: Parse FADT table to get PSCI flags for PSCI init
    Date
    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@linaro.org]
    > Sent: Tuesday, August 19, 2014 5:14 AM
    > To: Mark Rutland
    > Cc: Catalin Marinas; Rafael J. Wysocki; graeme.gregory@linaro.org; Arnd
    > Bergmann; Olof Johansson; grant.likely@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@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
    > kernel@vger.kernel.org; linaro-acpi@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:
    > >>>> @@ -47,6 +49,26 @@ void __init __acpi_unmap_table(char *map, unsigned
    > long size)
    > >>>> 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;
    > >>>> +
    > >>>> + /*
    > >>>> + * 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



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