Re: [PATCH v3 1/7] ACPI/PPTT: Add Processor Properties Topology Table parsing

[Jeremy Linton]

Hi,

On 10/17/2017 08:25 AM, Tomasz Nowicki wrote:
> Hi Jeremy,
>
> I did second round of review and have some more comments, please see below:
>
> On 12.10.2017 21:48, 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.
> >
> > Further, report peers in the topology using setup_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>
> > ---
> > Â drivers/acpi/pptt.c | 485 
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++
> > Â 1 file changed, 485 insertions(+)
> > Â 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..c86715fed4a7
> > --- /dev/null
> > +++ b/drivers/acpi/pptt.c
> > @@ -0,1 +1,485 @@
> > +/*
> > + * Copyright (C) 2017, 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.
> > + */
> > +#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
> > + */
> > +static struct acpi_subtable_header *fetch_pptt_subtable(
> > +ÂÂÂ struct acpi_table_header *table_hdr, u32 pptt_ref)
> > +{
> > +ÂÂÂ struct acpi_subtable_header *entry;
> > +
> > +ÂÂÂ /* there isn't a subtable at reference 0 */
> > +ÂÂÂ if (!pptt_ref)
> > +ÂÂÂÂÂÂÂ return NULL;
> > +
> > +ÂÂÂ if (pptt_ref + sizeof(struct acpi_subtable_header) > 
> > table_hdr->length)
> > +ÂÂÂÂÂÂÂ return NULL;
> > +
> > +ÂÂÂ entry = (struct acpi_subtable_header *)((u8 *)table_hdr + pptt_ref);
> > +
> > +ÂÂÂ if (pptt_ref + entry->length > table_hdr->length)
> > +ÂÂÂÂÂÂÂ return NULL;
> > +
> > +ÂÂÂ return entry;
> > +}
> > +
> > +static struct acpi_pptt_processor *fetch_pptt_node(
> > +ÂÂÂ struct acpi_table_header *table_hdr, u32 pptt_ref)
> > +{
> > +ÂÂÂ return (struct acpi_pptt_processor 
> > *)fetch_pptt_subtable(table_hdr, pptt_ref);
> > +}
> > +
> > +static struct acpi_pptt_cache *fetch_pptt_cache(
> > +ÂÂÂ struct acpi_table_header *table_hdr, u32 pptt_ref)
> > +{
> > +ÂÂÂ return (struct acpi_pptt_cache *)fetch_pptt_subtable(table_hdr, 
> > pptt_ref);
> > +}
> > +
> > +static struct acpi_subtable_header *acpi_get_pptt_resource(
> > +ÂÂÂ struct acpi_table_header *table_hdr,
> > +ÂÂÂ struct acpi_pptt_processor *node, int resource)
> > +{
> > +ÂÂÂ u32 ref;
> > +
> > +ÂÂÂ if (resource >= node->number_of_priv_resources)
> > +ÂÂÂÂÂÂÂ return NULL;
> > +
> > +ÂÂÂ ref = *(u32 *)((u8 *)node + sizeof(struct acpi_pptt_processor) +
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂ sizeof(u32) * resource);
> > +
> > +ÂÂÂ return fetch_pptt_subtable(table_hdr, ref);
> > +}
> > +
> > +/*
> > + * 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,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ int local_level,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct acpi_subtable_header *res,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct acpi_pptt_cache **found,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ int level, int type)
> > +{
> > +ÂÂÂ struct acpi_pptt_cache *cache;
> > +
> > +ÂÂÂ if (res->type != ACPI_PPTT_TYPE_CACHE)
> > +ÂÂÂÂÂÂÂ return 0;
> > +
> > +ÂÂÂ cache = (struct acpi_pptt_cache *) res;
> > +ÂÂÂ while (cache) {
> > +ÂÂÂÂÂÂÂ local_level++;
> > +
> > +ÂÂÂÂÂÂÂ if ((local_level == level) &&
> > +ÂÂÂÂÂÂÂÂÂÂÂ (cache->flags & ACPI_PPTT_CACHE_TYPE_VALID) &&
> > +ÂÂÂÂÂÂÂÂÂÂÂ ((cache->attributes & ACPI_PPTT_MASK_CACHE_TYPE) == type)) {
>
> Attributes have to be shifted:
>
> (cache->attributes & ACPI_PPTT_MASK_CACHE_TYPE) >> 2

Hmmm, I'm not sure that is true, the top level function in this routine 
convert the "linux" constant to the ACPI version of that constant. In 
that case the "type" field is pre-shifted, so that it matches the result 
of just anding against the field... That is unless I messed something 
up, which I don't see at the moment (and the code of course has been 
tested with PPTT's from multiple people at this point).


> > +ÂÂÂÂÂÂÂÂÂÂÂ if (*found != NULL)
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_err("Found duplicate cache level/type unable to 
> > determine uniqueness\n");
> > +
> > +ÂÂÂÂÂÂÂÂÂÂÂ pr_debug("Found cache @ level %d\n", level);
> > +ÂÂÂÂÂÂÂÂÂÂÂ *found = cache;
> > +ÂÂÂÂÂÂÂÂÂÂÂ /*
> > +ÂÂÂÂÂÂÂÂÂÂÂÂ * continue looking at this node's resource list
> > +ÂÂÂÂÂÂÂÂÂÂÂÂ * to verify that we don't find a duplicate
> > +ÂÂÂÂÂÂÂÂÂÂÂÂ * cache node.
> > +ÂÂÂÂÂÂÂÂÂÂÂÂ */
> > +ÂÂÂÂÂÂÂ }
> > +ÂÂÂÂÂÂÂ cache = fetch_pptt_cache(table_hdr, cache->next_level_of_cache);
> > +ÂÂÂ }
> > +ÂÂÂ return local_level;
> > +}
> > +
> > +/*
> > + * Given a CPU node look for cache levels that exist at this level, 
> > and then
> > + * for each cache node, count how many levels exist below (logically 
> > above) it.
> > + * If a level and type are specified, and we find that level/type, abort
> > + * processing and return the acpi_pptt_cache structure.
> > + */
> > +static struct acpi_pptt_cache *acpi_find_cache_level(
> > +ÂÂÂ struct acpi_table_header *table_hdr,
> > +ÂÂÂ struct acpi_pptt_processor *cpu_node,
> > +ÂÂÂ int *starting_level, int level, int type)
> > +{
> > +ÂÂÂ struct acpi_subtable_header *res;
> > +ÂÂÂ int number_of_levels = *starting_level;
> > +ÂÂÂ int resource = 0;
> > +ÂÂÂ struct acpi_pptt_cache *ret = NULL;
> > +ÂÂÂ int local_level;
> > +
> > +ÂÂÂ /* walk down from the processor node */
> > +ÂÂÂ while ((res = acpi_get_pptt_resource(table_hdr, cpu_node, 
> > resource))) {
> > +ÂÂÂÂÂÂÂ resource++;
> > +
> > +ÂÂÂÂÂÂÂ local_level = acpi_pptt_walk_cache(table_hdr, *starting_level,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ res, &ret, level, type);
> > +ÂÂÂÂÂÂÂ /*
> > +ÂÂÂÂÂÂÂÂ * we are looking for the max depth. Since its potentially
> > +ÂÂÂÂÂÂÂÂ * possible for a given node to have resources with differing
> > +ÂÂÂÂÂÂÂÂ * depths verify that the depth we have found is the largest.
> > +ÂÂÂÂÂÂÂÂ */
> > +ÂÂÂÂÂÂÂ if (number_of_levels < local_level)
> > +ÂÂÂÂÂÂÂÂÂÂÂ number_of_levels = local_level;
> > +ÂÂÂ }
> > +ÂÂÂ if (number_of_levels > *starting_level)
> > +ÂÂÂÂÂÂÂ *starting_level = number_of_levels;
> > +
> > +ÂÂÂ return ret;
> > +}
> > +
> > +/*
> > + * given a processor node containing a processing unit, walk into it 
> > and count
> > + * how many levels exist solely for it, and then walk up each level 
> > until we hit
> > + * the root node (ignore the package level because it may be possible 
> > to have
> > + * caches that exist across packages). Count the number of cache 
> > levels that
> > + * exist at each level on the way up.
> > + */
> > +static int acpi_process_node(struct acpi_table_header *table_hdr,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct acpi_pptt_processor *cpu_node)
> > +{
> > +ÂÂÂ int total_levels = 0;
> > +
> > +ÂÂÂ do {
> > +ÂÂÂÂÂÂÂ acpi_find_cache_level(table_hdr, cpu_node, &total_levels, 0, 0);
> > +ÂÂÂÂÂÂÂ cpu_node = fetch_pptt_node(table_hdr, cpu_node->parent);
> > +ÂÂÂ } while (cpu_node);
> > +
> > +ÂÂÂ return total_levels;
> > +}
> > +
> > +/* determine if the given node is a leaf node */
> > +static int acpi_pptt_leaf_node(struct acpi_table_header *table_hdr,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct acpi_pptt_processor *node)
> > +{
> > +ÂÂÂ struct acpi_subtable_header *entry;
> > +ÂÂÂ unsigned long table_end;
> > +ÂÂÂ u32 node_entry;
> > +ÂÂÂ struct acpi_pptt_processor *cpu_node;
> > +
> > +ÂÂÂ table_end = (unsigned long)table_hdr + table_hdr->length;
> > +ÂÂÂ node_entry = (u32)((u8 *)node - (u8 *)table_hdr);
> > +ÂÂÂ entry = (struct acpi_subtable_header *)((u8 *)table_hdr +
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ sizeof(struct acpi_table_pptt));
> > +
> > +ÂÂÂ while (((unsigned long)entry) + sizeof(struct 
> > acpi_subtable_header) < table_end) {
> > +ÂÂÂÂÂÂÂ cpu_node = (struct acpi_pptt_processor *)entry;
> > +ÂÂÂÂÂÂÂ if ((entry->type == ACPI_PPTT_TYPE_PROCESSOR) &&
> > +ÂÂÂÂÂÂÂÂÂÂÂ (cpu_node->parent == node_entry))
> > +ÂÂÂÂÂÂÂÂÂÂÂ return 0;
> > +ÂÂÂÂÂÂÂ entry = (struct acpi_subtable_header *)((u8 *)entry + 
> > entry->length);
> > +ÂÂÂ }
> > +ÂÂÂ return 1;
> > +}
> > +
> > +/*
> > + * Find the subtable entry describing the provided processor
> > + */
> > +static struct acpi_pptt_processor *acpi_find_processor_node(
> > +ÂÂÂ struct acpi_table_header *table_hdr,
> > +ÂÂÂ u32 acpi_cpu_id)
> > +{
> > +ÂÂÂ struct acpi_subtable_header *entry;
> > +ÂÂÂ unsigned long table_end;
> > +ÂÂÂ struct acpi_pptt_processor *cpu_node;
> > +
> > +ÂÂÂ table_end = (unsigned long)table_hdr + table_hdr->length;
> > +ÂÂÂ entry = (struct acpi_subtable_header *)((u8 *)table_hdr +
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ sizeof(struct acpi_table_pptt));
> > +
> > +ÂÂÂ /* find the processor structure associated with this cpuid */
> > +ÂÂÂ while (((unsigned long)entry) + sizeof(struct 
> > acpi_subtable_header) < table_end) {
> > +ÂÂÂÂÂÂÂ cpu_node = (struct acpi_pptt_processor *)entry;
> > +
> > +ÂÂÂÂÂÂÂ if ((entry->type == ACPI_PPTT_TYPE_PROCESSOR) &&
> > +ÂÂÂÂÂÂÂÂÂÂÂ acpi_pptt_leaf_node(table_hdr, cpu_node)) {
> > +ÂÂÂÂÂÂÂÂÂÂÂ pr_debug("checking phy_cpu_id %d against acpi id %d\n",
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ acpi_cpu_id, cpu_node->acpi_processor_id);
> > +ÂÂÂÂÂÂÂÂÂÂÂ if (acpi_cpu_id == cpu_node->acpi_processor_id) {
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /* found the correct entry */
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_debug("match found!\n");
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return (struct acpi_pptt_processor *)entry;
> > +ÂÂÂÂÂÂÂÂÂÂÂ }
> > +ÂÂÂÂÂÂÂ }
> > +
> > +ÂÂÂÂÂÂÂ if (entry->length == 0) {
> > +ÂÂÂÂÂÂÂÂÂÂÂ pr_err("Invalid zero length subtable\n");
> > +ÂÂÂÂÂÂÂÂÂÂÂ break;
> > +ÂÂÂÂÂÂÂ }
> > +ÂÂÂÂÂÂÂ entry = (struct acpi_subtable_header *)
> > +ÂÂÂÂÂÂÂÂÂÂÂ ((u8 *)entry + entry->length);
> > +ÂÂÂ }
> > +
> > +ÂÂÂ return NULL;
> > +}
> > +
> > +/*
> > + * Given a acpi_pptt_processor node, walk up until we identify the
> > + * package that the node is associated with or we run out of levels
> > + * to request.
> > + */
> > +static struct acpi_pptt_processor *acpi_find_processor_package_id(
> > +ÂÂÂ struct acpi_table_header *table_hdr,
> > +ÂÂÂ struct acpi_pptt_processor *cpu,
> > +ÂÂÂ int level)
> > +{
> > +ÂÂÂ struct acpi_pptt_processor *prev_node;
> > +
> > +ÂÂÂ while (cpu && level && !(cpu->flags & ACPI_PPTT_PHYSICAL_PACKAGE)) {
> > +ÂÂÂÂÂÂÂ pr_debug("level %d\n", level);
> > +ÂÂÂÂÂÂÂ prev_node = fetch_pptt_node(table_hdr, cpu->parent);
> > +ÂÂÂÂÂÂÂ if (prev_node == NULL)
> > +ÂÂÂÂÂÂÂÂÂÂÂ break;
> > +ÂÂÂÂÂÂÂ cpu = prev_node;
> > +ÂÂÂÂÂÂÂ level--;
> > +ÂÂÂ }
> > +ÂÂÂ return cpu;
> > +}
> > +
> > +static int acpi_parse_pptt(struct acpi_table_header *table_hdr, u32 
> > acpi_cpu_id)
>
> The function name can be more descriptive. How about:
>
> acpi_count_cache_level() ?

The naming has drifted a bit, so yes, that routine is only used by the 
portion which is determining the number of cache levels for a given PE.


> > +{
> > +ÂÂÂ int number_of_levels = 0;
> > +ÂÂÂ struct acpi_pptt_processor *cpu;
> > +
> > +ÂÂÂ cpu = acpi_find_processor_node(table_hdr, acpi_cpu_id);
> > +ÂÂÂ if (cpu)
> > +ÂÂÂÂÂÂÂ number_of_levels = acpi_process_node(table_hdr, cpu);
> > +
> > +ÂÂÂ return number_of_levels;
> > +}
>
> It is hard to follow what acpi_find_cache_level() and 
> acpi_pptt_walk_cache() really do. It is because they are trying to do 
> too many things at the same time. IMO, splitting acpi_find_cache_level() 
> logic to:
> 1. counting the cache levels (max depth)
> 2. finding the specific cache node
> makes sense.

I disagree, that routine is shared by the two code paths because its 
functionality is 99% duplicated between the two. The difference being 
whether it terminates the search at a given level, or continues 
searching until it runs out of nodes. The latter case is simply a 
degenerate version of the first.


> Also, seems like we can merge acpi_parse_pptt() & acpi_process_node().

That is true, but I fail to see how any of this is actually fixes 
anything. There are a million ways to do this, including as pointed out 
by building another data-structure to simplify the parsing what is a 
table that is less than ideal for runtime parsing (starting with the 
direction of the relative pointers, and ending with having to "infer" 
information that isn't directly flagged). I actually built a couple 
other versions of this, including a nice cute version which is about 1/8 
this size of this and really easy to understand but of course is 
recursive...


> Here are my suggestions:
>
>
> static struct acpi_pptt_cache *acpi_pptt_cache_type_level(
>  ÂÂÂÂstruct acpi_table_header *table_hdr,
>  ÂÂÂÂstruct acpi_subtable_header *res,
>  ÂÂÂÂint *local_level,
>  ÂÂÂÂint level, int type)
> {
>  ÂÂÂÂstruct acpi_pptt_cache *cache = (struct acpi_pptt_cache *) res;
>
>  ÂÂÂÂif (res->type != ACPI_PPTT_TYPE_CACHE)
>  ÂÂÂÂÂÂÂ return NULL;
>
>  ÂÂÂÂwhile (cache) {
>  ÂÂÂÂÂÂÂ if ((*local_level == level) &&
>  ÂÂÂÂÂÂÂÂÂÂÂ (cache->flags & ACPI_PPTT_CACHE_TYPE_VALID) &&
>  ÂÂÂÂÂÂÂÂÂÂÂ ((cache->attributes & ACPI_PPTT_MASK_CACHE_TYPE) >> 2 == 
> type)) {
>
>  ÂÂÂÂÂÂÂÂÂÂÂ pr_debug("Found cache @ level %d\n", level);
>  ÂÂÂÂÂÂÂÂÂÂÂ return cache;
>  ÂÂÂÂÂÂÂ }
>  ÂÂÂÂÂÂÂ cache = fetch_pptt_cache(table_hdr, cache->next_level_of_cache);
>  ÂÂÂÂÂÂÂ (*local_level)++;
>  ÂÂÂÂ}
>  ÂÂÂÂreturn NULL;
> }
>
> static struct acpi_pptt_cache *_acpi_find_cache_node(
>  ÂÂÂÂstruct acpi_table_header *table_hdr,
>  ÂÂÂÂstruct acpi_pptt_processor *cpu_node,
>  ÂÂÂÂint *local_level, int level, int type)
> {
>  ÂÂÂÂstruct acpi_subtable_header *res;
>  ÂÂÂÂstruct acpi_pptt_cache *cache_tmp, *cache = NULL;
>  ÂÂÂÂint resource = 0;
>
>  ÂÂÂÂ/* walk down from the processor node */
>  ÂÂÂÂwhile ((res = acpi_get_pptt_resource(table_hdr, cpu_node, 
> resource))) {
>
>  ÂÂÂÂÂÂÂ cache_tmp = acpi_pptt_cache_type_level(table_hdr, res,
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ local_level, level, type);
>  ÂÂÂÂÂÂÂ if (cache_tmp) {
>  ÂÂÂÂÂÂÂÂÂÂÂ if (cache)
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_err("Found duplicate cache level/type unable to 
> determine uniqueness\n");
>
>  ÂÂÂÂÂÂÂÂÂÂÂ cache = cache_tmp;
>  ÂÂÂÂÂÂÂ }
>  ÂÂÂÂÂÂÂ resource++;
>  ÂÂÂÂ}
>  ÂÂÂÂreturn cache;
> }
>
> /* find the ACPI node describing the cache type/level for the given CPU */
> static struct acpi_pptt_cache *acpi_find_cache_node(
>  ÂÂÂÂstruct acpi_table_header *table_hdr, u32 acpi_cpu_id,
>  ÂÂÂÂenum cache_type type, unsigned int level,
>  ÂÂÂÂstruct acpi_pptt_processor **node)
> {
>  ÂÂÂÂint total_levels = 0;
>  ÂÂÂÂstruct acpi_pptt_cache *found = NULL;
>  ÂÂÂÂstruct acpi_pptt_processor *cpu_node;
>  ÂÂÂÂu8 acpi_type = acpi_cache_type(type);
>
>  ÂÂÂÂpr_debug("Looking for CPU %d's level %d cache type %d\n",
>  ÂÂÂÂÂÂÂÂ acpi_cpu_id, level, acpi_type);
>
>  ÂÂÂÂcpu_node = acpi_find_processor_node(table_hdr, acpi_cpu_id);
>  ÂÂÂÂif (!cpu_node)
>  ÂÂÂÂÂÂÂ return NULL;
>
>  ÂÂÂÂdo {
>  ÂÂÂÂÂÂÂ found = _acpi_find_cache_node(table_hdr, cpu_node,
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ &total_levels, level, acpi_type);
>  ÂÂÂÂÂÂÂ *node = cpu_node;
>  ÂÂÂÂÂÂÂ cpu_node = fetch_pptt_node(table_hdr, cpu_node->parent);
>  ÂÂÂÂ} while ((cpu_node) && (!found));
>
>  ÂÂÂÂreturn found;
> }
>
> static int acpi_pptt_cache_level(struct acpi_table_header *table_hdr,
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct acpi_subtable_header *res)
> {
>  ÂÂÂÂstruct acpi_pptt_cache *cache = (struct acpi_pptt_cache *) res;
>  ÂÂÂÂint local_level = 1;
>
>  ÂÂÂÂif (res->type != ACPI_PPTT_TYPE_CACHE)
>  ÂÂÂÂÂÂÂ return 0;
>
>  ÂÂÂÂwhile ((cache = fetch_pptt_cache(table_hdr, 
> cache->next_level_of_cache)))
>  ÂÂÂÂÂÂÂ local_level++;
>  ÂÂÂÂreturn local_level;
> }
>
> static int _acpi_count_cache_level(
>  ÂÂÂÂstruct acpi_table_header *table_hdr,
>  ÂÂÂÂstruct acpi_pptt_processor *cpu_node)
> {
>  ÂÂÂÂstruct acpi_subtable_header *res;
>  ÂÂÂÂint levels = 0, resource = 0, number_of_levels = 0;
>
>  ÂÂÂÂ/* walk down from the processor node */
>  ÂÂÂÂwhile ((res = acpi_get_pptt_resource(table_hdr, cpu_node, 
> resource))) {
>  ÂÂÂÂÂÂÂ levels = acpi_pptt_cache_level(table_hdr, res);
>
>  ÂÂÂÂÂÂÂ /*
>  ÂÂÂÂÂÂÂÂ * we are looking for the max depth. Since its potentially
>  ÂÂÂÂÂÂÂÂ * possible for a given node to have resources with differing
>  ÂÂÂÂÂÂÂÂ * depths verify that the depth we have found is the largest.
>  ÂÂÂÂÂÂÂÂ */
>  ÂÂÂÂÂÂÂ if (levels > number_of_levels)
>  ÂÂÂÂÂÂÂÂÂÂÂ number_of_levels = levels;
>
>  ÂÂÂÂÂÂÂ resource++;
>  ÂÂÂÂ}
>  ÂÂÂÂreturn number_of_levels;
> }
>
> static int acpi_count_cache_level(struct acpi_table_header *table_hdr,
>  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ u32 acpi_cpu_id)
> {
>  ÂÂÂÂint total_levels = 0;
>  ÂÂÂÂstruct acpi_pptt_processor *cpu_node;
>
>  ÂÂÂÂcpu_node = acpi_find_processor_node(table_hdr, acpi_cpu_id);
>  ÂÂÂÂwhile (cpu_node) {
>  ÂÂÂÂÂÂÂ total_levels += _acpi_count_cache_level(table_hdr, cpu_node);
>  ÂÂÂÂÂÂÂ cpu_node = fetch_pptt_node(table_hdr, cpu_node->parent);
>  ÂÂÂÂ}
>
>  ÂÂÂÂreturn total_levels;
> }
>
>
> Did not compile the code so I may have missed somthing.
>
> Thanks,
> Tomasz