linux-kernel - Re: [PATCH v9 05/12] ACPI/PPTT: Add Processor Properties Topology Table parsing

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Message-ID: <CAJZ5v0h4OeTaG2h0Q1c8zX93tici_nfLftpEyKWSkXoztHuUDg@mail.gmail.com>
Date:   Sat, 12 May 2018 12:09:40 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Sudeep Holla <Sudeep.Holla@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Will Deacon <Will.Deacon@....com>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <Mark.Rutland@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv@...ts.infradead.org, wangxiongfeng2@...wei.com,
        vkilari@...eaurora.org, Al Stone <ahs3@...hat.com>,
        Dietmar Eggemann <Dietmar.Eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>, palmer@...ive.com,
        Len Brown <lenb@...nel.org>,
        John Garry <john.garry@...wei.com>, austinwc@...eaurora.org,
        tnowicki@...iumnetworks.com, jhugo@...eaurora.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH v9 05/12] ACPI/PPTT: Add Processor Properties Topology
 Table parsing

On Sat, May 12, 2018 at 1:58 AM, Jeremy Linton <jeremy.linton@....com> wrote:
> ACPI 6.2 adds a new table, which describes how processing units
> are related to each other in tree like fashion. Caches are
> also sprinkled throughout the tree and describe the properties
> of the caches in relation to other caches and processing units.
>
> Add the code to parse the cache hierarchy and report the total
> number of levels of cache for a given core using
> acpi_find_last_cache_level() as well as fill out the individual
> cores cache information with cache_setup_acpi() once the
> cpu_cacheinfo structure has been populated by the arch specific
> code.
>
> An additional patch later in the set adds the ability to report
> peers in the topology using find_acpi_cpu_topology()
> to report a unique ID for each processing unit at a given level
> in the tree. These unique id's can then be used to match related
> processing units which exist as threads, within a given
> package, etc.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
> Tested-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Tested-by: Vijaya Kumar K <vkilari@...eaurora.org>
> Tested-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
> Tested-by: Tomasz Nowicki <Tomasz.Nowicki@...ium.com>
> Acked-by: Sudeep Holla <sudeep.holla@....com>
> Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
>  drivers/acpi/pptt.c  | 655 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/acpi.h |   4 +
>  2 files changed, 659 insertions(+)
>  create mode 100644 drivers/acpi/pptt.c
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> new file mode 100644
> index 000000000000..e5ea1974d1e3
> --- /dev/null
> +++ b/drivers/acpi/pptt.c
> @@ -0,0 +1,655 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * pptt.c - parsing of Processor Properties Topology Table (PPTT)
> + *
> + * Copyright (C) 2018, ARM
> + *
> + * This file implements parsing of the Processor Properties Topology Table
> + * which is optionally used to describe the processor and cache topology.
> + * Due to the relative pointers used throughout the table, this doesn't
> + * leverage the existing subtable parsing in the kernel.
> + *
> + * The PPTT structure is an inverted tree, with each node potentially
> + * holding one or two inverted tree data structures describing
> + * the caches available at that level. Each cache structure optionally
> + * contains properties describing the cache at a given level which can be
> + * used to override hardware probed values.
> + */
> +#define pr_fmt(fmt) "ACPI PPTT: " fmt
> +
> +#include <linux/acpi.h>
> +#include <linux/cacheinfo.h>
> +#include <acpi/processor.h>
> +
> +static struct acpi_subtable_header *fetch_pptt_subtable(struct acpi_table_header *table_hdr,
> +                                                       u32 pptt_ref)
> +{
> +       struct acpi_subtable_header *entry;
> +
> +       /* there isn't a subtable at reference 0 */
> +       if (pptt_ref < sizeof(struct acpi_subtable_header))
> +               return NULL;
> +
> +       if (pptt_ref + sizeof(struct acpi_subtable_header) > table_hdr->length)
> +               return NULL;
> +
> +       entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr, pptt_ref);
> +
> +       if (entry->length == 0)
> +               return NULL;
> +
> +       if (pptt_ref + entry->length > table_hdr->length)
> +               return NULL;
> +
> +       return entry;
> +}
> +
> +static struct acpi_pptt_processor *fetch_pptt_node(struct acpi_table_header *table_hdr,
> +                                                  u32 pptt_ref)
> +{
> +       return (struct acpi_pptt_processor *)fetch_pptt_subtable(table_hdr, pptt_ref);
> +}
> +
> +static struct acpi_pptt_cache *fetch_pptt_cache(struct acpi_table_header *table_hdr,
> +                                               u32 pptt_ref)
> +{
> +       return (struct acpi_pptt_cache *)fetch_pptt_subtable(table_hdr, pptt_ref);

I don't think you really need the explicit type cast here and above,
but that's very minor.

> +}

Please feel free to add

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

to the patch and route it through the arch tree as needed.

Thanks,
Rafael