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    SubjectRe: [PATCH v7 05/13] ACPI/PPTT: Add Processor Properties Topology Table parsing
    Date
    On Wednesday, February 28, 2018 11:06:11 PM CET Jeremy Linton 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, COD (clusters
    > on die), within a given package, etc.
    >
    > Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>

    A couple of cosmetic comments.

    > ---
    > drivers/acpi/pptt.c | 488 ++++++++++++++++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 488 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..883e4318c6cd
    > --- /dev/null
    > +++ b/drivers/acpi/pptt.c
    > @@ -0,0 +1,488 @@

    Use an SPDX license ID here and then you don't need the license boilerplate
    below.

    > +/*
    > + * Copyright (C) 2018, ARM
    > + *
    > + * This program is free software; you can redistribute it and/or modify it
    > + * under the terms and conditions of the GNU General Public License,
    > + * version 2, as published by the Free Software Foundation.
    > + *
    > + * This program is distributed in the hope it will be useful, but WITHOUT
    > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
    > + * more details.
    > + *
    > + * This file implements parsing of Processor Properties Topology Table (PPTT)
    > + * 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>
    > +
    > +/*
    > + * Given the PPTT table, find and verify that the subtable entry
    > + * is located within the table
    > + */

    If you add a comment above a function, make it a kerneldoc. That
    never hurts, but really helps sometimes.

    > +static struct acpi_subtable_header *fetch_pptt_subtable(

    Don't break the line here, it can be broken after the first arg.

    That's OK even if it is more than 80 chars long.

    > + 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 (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);

    You don't need to break this line too.

    > +}
    > +
    > +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);

    And here.

    > +}
    > +
    > +static struct acpi_subtable_header *acpi_get_pptt_resource(
    > + struct acpi_table_header *table_hdr,
    > + struct acpi_pptt_processor *node, int resource)
    > +{
    > + u32 *ref;
    > +
    > + if (resource >= node->number_of_priv_resources)
    > + return NULL;
    > +
    > + ref = ACPI_ADD_PTR(u32, node, sizeof(struct acpi_pptt_processor));
    > + ref += resource;
    > +
    > + return fetch_pptt_subtable(table_hdr, *ref);
    > +}
    > +
    > +/*
    > + * Match the type passed and special case the TYPE_UNIFIED so that
    > + * it match both ACPI_PPTT_CACHE_TYPE_UNIFIED(_ALT) types.
    > + */
    > +static inline bool acpi_pptt_match_type(int table_type, int type)
    > +{
    > + return (((table_type & ACPI_PPTT_MASK_CACHE_TYPE) == type) ||
    > + (table_type & ACPI_PPTT_CACHE_TYPE_UNIFIED & type));
    > +}
    > +
    > +/*
    > + * Attempt to find a given cache level, while counting the max number
    > + * of cache levels for the cache node.
    > + *
    > + * Given a pptt resource, verify that it is a cache node, then walk
    > + * down each level of caches, counting how many levels are found
    > + * as well as checking the cache type (icache, dcache, unified). If a
    > + * level & type match, then we set found, and continue the search.
    > + * Once the entire cache branch has been walked return its max
    > + * depth.
    > + */
    > +static int acpi_pptt_walk_cache(struct acpi_table_header *table_hdr,
    > + int local_level,
    > + struct acpi_subtable_header *res,
    > + struct acpi_pptt_cache **found,
    > + int level, int type)
    > +{
    > + struct acpi_pptt_cache *cache;
    > +
    > + if (res->type != ACPI_PPTT_TYPE_CACHE)
    > + return 0;
    > +
    > + cache = (struct acpi_pptt_cache *) res;
    > + while (cache) {
    > + local_level++;
    > +
    > + if ((local_level == level) &&
    > + (cache->flags & ACPI_PPTT_CACHE_TYPE_VALID) &&
    > + acpi_pptt_match_type(cache->attributes, type)) {
    > + if ((*found != NULL) && (cache != *found))

    Inner parens are not necessary (and above and in some other places too).

    > + pr_err("Found duplicate cache level/type unable to determine uniqueness\n");

    This is not an error, rather a statement that something is inconsistent in the
    ACPI table, so please consider using a different log level here.

    [cut]

    I guess I could post similar comments for the other general ACPI patches in
    this series, so please address them in there too if applicable.

    Thanks!

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