Re: [PATCH v6 05/12] ACPI/PPTT: Add Processor Properties Topology Table parsing

From: Jeremy Linton
Date: Tue Jan 16 2018 - 15:22:30 EST

Hi,

On 01/15/2018 09:48 AM, Sudeep Holla wrote:
On Fri, Jan 12, 2018 at 06:59:13PM -0600, 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@xxxxxxx>
---
drivers/acpi/pptt.c | 476 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 476 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..2c4b3ed862a8
--- /dev/null
+++ b/drivers/acpi/pptt.c
@@ -0,0 +1,476 @@
+/*
+ * 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>
+
+/* total number of attributes checked by the properties code */
+#define PPTT_CHECKED_ATTRIBUTES 6
+
+/*
+ * Given the PPTT table, find and verify that the subtable entry
+ * is located within the table
+ */
+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 (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);
+}
+
+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);
+}
+
+/*
+ * 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) &&
+ ((cache->attributes & ACPI_PPTT_MASK_CACHE_TYPE) == type)) {
+ if ((*found != NULL) && (cache != *found))

I forgot to mention this earlier, I see you have used parentheses too
liberally at quite some place in this file like the above 4 line.
Please drop those unnecessary parentheses.

Yes, those tend to get leftover when I remove code, I realized not long after posting this that in one of the previous patches I actually added a pair where there wasn't one because I first shuffled something into the if condition, then a few revisions later dropped it, and when I squashed it before posting the result was some pointless churn.

I will rescan the whole set for this.