linux-kernel - Re: [PATCH v5 1/4] ACPI/PPTT: Modify node flag detection to find last IDENTICAL

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Date:   Thu, 27 Jun 2019 13:15:00 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Hanjun Gou <gouhanjun@...wei.com>
Subject: Re: [PATCH v5 1/4] ACPI/PPTT: Modify node flag detection to find last IDENTICAL

On Wed, Jun 26, 2019 at 11:37 PM Jeremy Linton <jeremy.linton@....com> wrote:
>
> The ACPI specification implies that the IDENTICAL flag should be
> set on all non leaf nodes where the children are identical.
> This means that we need to be searching for the last node with
> the identical flag set rather than the first one.
>
> Since this flag is also dependent on the table revision, we
> need to add a bit of extra code to verify the table revision,
> and the next node's state in the traversal. Since we want to
> avoid function pointers here, lets just special case
> the IDENTICAL flag.
>
> Tested-by: Hanjun Gou <gouhanjun@...wei.com>
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
> Signed-off-by: Jeremy Linton <jeremy.linton@....com>

Assuming that the Tested-by tag will be fixed:

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
>  drivers/acpi/pptt.c | 35 +++++++++++++++++++++++++++++------
>  1 file changed, 29 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index b72e6afaa8fb..05344413f199 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -432,17 +432,40 @@ static void cache_setup_acpi_cpu(struct acpi_table_header *table,
>         }
>  }
>
> +static bool flag_identical(struct acpi_table_header *table_hdr,
> +                          struct acpi_pptt_processor *cpu)
> +{
> +       struct acpi_pptt_processor *next;
> +
> +       /* heterogeneous machines must use PPTT revision > 1 */
> +       if (table_hdr->revision < 2)
> +               return false;
> +
> +       /* Locate the last node in the tree with IDENTICAL set */
> +       if (cpu->flags & ACPI_PPTT_ACPI_IDENTICAL) {
> +               next = fetch_pptt_node(table_hdr, cpu->parent);
> +               if (!(next && next->flags & ACPI_PPTT_ACPI_IDENTICAL))
> +                       return true;
> +       }
> +
> +       return false;
> +}
> +
>  /* Passing level values greater than this will result in search termination */
>  #define PPTT_ABORT_PACKAGE 0xFF
>
> -static struct acpi_pptt_processor *acpi_find_processor_package_id(struct acpi_table_header *table_hdr,
> -                                                                 struct acpi_pptt_processor *cpu,
> -                                                                 int level, int flag)
> +static struct acpi_pptt_processor *acpi_find_processor_tag(struct acpi_table_header *table_hdr,
> +                                                          struct acpi_pptt_processor *cpu,
> +                                                          int level, int flag)
>  {
>         struct acpi_pptt_processor *prev_node;
>
>         while (cpu && level) {
> -               if (cpu->flags & flag)
> +               /* special case the identical flag to find last identical */
> +               if (flag == ACPI_PPTT_ACPI_IDENTICAL) {
> +                       if (flag_identical(table_hdr, cpu))
> +                               break;
> +               } else if (cpu->flags & flag)
>                         break;
>                 pr_debug("level %d\n", level);
>                 prev_node = fetch_pptt_node(table_hdr, cpu->parent);
> @@ -480,8 +503,8 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table,
>
>         cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
>         if (cpu_node) {
> -               cpu_node = acpi_find_processor_package_id(table, cpu_node,
> -                                                         level, flag);
> +               cpu_node = acpi_find_processor_tag(table, cpu_node,
> +                                                  level, flag);
>                 /*
>                  * As per specification if the processor structure represents
>                  * an actual processor, then ACPI processor ID must be valid.
> --
> 2.21.0
>