powerpc: Rewrite sysfs processor cache info code

The current code for providing processor cache information in sysfs
has the following deficiencies:
- several complex functions that are hard to understand
- implicit recursion (cache_desc_release -> kobject_put -> cache_desc_release)
- explicit recursion (create_cache_index_info)
- use of two per-cpu arrays when one would suffice
- duplication of work on systems where CPUs share cache

Also, when I looked at implementing support for a shared_cpu_map
attribute, it was pretty much impossible to handle hotplug without
checking every single online CPU's cache_desc list and fixing things
up... not that this is a hot path, but it would have introduced
O(n^2)-ish behavior during boot.  Addressing this involved rethinking
the core data structures used, which didn't lend itself to an
incremental approach.

This implementation maintains a "forest" (potentially more than one
tree) of cache objects which reflects the system's cache topology.
Cache objects are instantiated as needed as CPUs come online.  A
per-cpu array is used mainly for sysfs-related bookkeeping; the
objects in the array just point to the appropriate points in the
forest.

This maintains compatibility with the existing code and includes some
enhancements:
- Implement the shared_cpu_map attribute, which is essential for
  enabling userspace to discover the system's overall cache topology.
- Use cache-block-size properties if cache-line-size is not available.

I chose to place this implementation in a new file since it would have
roughly doubled the size of sysfs.c, which is already kind of messy.
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/Makefile

@@ -29,7 +29,7 @@ endif
 obj-y				:= cputable.o ptrace.o syscalls.o \
 				   irq.o align.o signal_32.o pmc.o vdso.o \
 				   init_task.o process.o systbl.o idle.o \
-				   signal.o sysfs.o
+				   signal.o sysfs.o cacheinfo.o
 obj-y				+= vdso32/
 obj-$(CONFIG_PPC64)		+= setup_64.o sys_ppc32.o \
 				   signal_64.o ptrace32.o \

arch/powerpc/kernel/cacheinfo.h

+#ifndef _PPC_CACHEINFO_H
+#define _PPC_CACHEINFO_H
+
+/* These are just hooks for sysfs.c to use. */
+extern void cacheinfo_cpu_online(unsigned int cpu_id);
+extern void cacheinfo_cpu_offline(unsigned int cpu_id);
+
+#endif /* _PPC_CACHEINFO_H */

arch/powerpc/kernel/sysfs.c

@@ -18,6 +18,8 @@
 #include <asm/machdep.h>
 #include <asm/smp.h>
 
+#include "cacheinfo.h"
+
 #ifdef CONFIG_PPC64
 #include <asm/paca.h>
 #include <asm/lppaca.h>
@@ -25,8 +27,6 @@
 
 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 
-static DEFINE_PER_CPU(struct kobject *, cache_toplevel);
-
 /*
  * SMT snooze delay stuff, 64-bit only for now
  */
@@ -343,283 +343,6 @@ static struct sysdev_attribute pa6t_attrs[] = {
 #endif /* HAS_PPC_PMC_PA6T */
 #endif /* HAS_PPC_PMC_CLASSIC */
 
-struct cache_desc {
-	struct kobject kobj;
-	struct cache_desc *next;
-	const char *type;	/* Instruction, Data, or Unified */
-	u32 size;		/* total cache size in KB */
-	u32 line_size;		/* in bytes */
-	u32 nr_sets;		/* number of sets */
-	u32 level;		/* e.g. 1, 2, 3... */
-	u32 associativity;	/* e.g. 8-way... 0 is fully associative */
-};
-
-DEFINE_PER_CPU(struct cache_desc *, cache_desc);
-
-static struct cache_desc *kobj_to_cache_desc(struct kobject *k)
-{
-	return container_of(k, struct cache_desc, kobj);
-}
-
-static void cache_desc_release(struct kobject *k)
-{
-	struct cache_desc *desc = kobj_to_cache_desc(k);
-
-	pr_debug("%s: releasing %s\n", __func__, kobject_name(k));
-
-	if (desc->next)
-		kobject_put(&desc->next->kobj);
-
-	kfree(kobj_to_cache_desc(k));
-}
-
-static ssize_t cache_desc_show(struct kobject *k, struct attribute *attr, char *buf)
-{
-	struct kobj_attribute *kobj_attr;
-
-	kobj_attr = container_of(attr, struct kobj_attribute, attr);
-
-	return kobj_attr->show(k, kobj_attr, buf);
-}
-
-static struct sysfs_ops cache_desc_sysfs_ops = {
-	.show = cache_desc_show,
-};
-
-static struct kobj_type cache_desc_type = {
-	.release = cache_desc_release,
-	.sysfs_ops = &cache_desc_sysfs_ops,
-};
-
-static ssize_t cache_size_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
-{
-	struct cache_desc *cache = kobj_to_cache_desc(k);
-
-	return sprintf(buf, "%uK\n", cache->size);
-}
-
-static struct kobj_attribute cache_size_attr =
-	__ATTR(size, 0444, cache_size_show, NULL);
-
-static ssize_t cache_line_size_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
-{
-	struct cache_desc *cache = kobj_to_cache_desc(k);
-
-	return sprintf(buf, "%u\n", cache->line_size);
-}
-
-static struct kobj_attribute cache_line_size_attr =
-	__ATTR(coherency_line_size, 0444, cache_line_size_show, NULL);
-
-static ssize_t cache_nr_sets_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
-{
-	struct cache_desc *cache = kobj_to_cache_desc(k);
-
-	return sprintf(buf, "%u\n", cache->nr_sets);
-}
-
-static struct kobj_attribute cache_nr_sets_attr =
-	__ATTR(number_of_sets, 0444, cache_nr_sets_show, NULL);
-
-static ssize_t cache_type_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
-{
-	struct cache_desc *cache = kobj_to_cache_desc(k);
-
-	return sprintf(buf, "%s\n", cache->type);
-}
-
-static struct kobj_attribute cache_type_attr =
-	__ATTR(type, 0444, cache_type_show, NULL);
-
-static ssize_t cache_level_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
-{
-	struct cache_desc *cache = kobj_to_cache_desc(k);
-
-	return sprintf(buf, "%u\n", cache->level);
-}
-
-static struct kobj_attribute cache_level_attr =
-	__ATTR(level, 0444, cache_level_show, NULL);
-
-static ssize_t cache_assoc_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
-{
-	struct cache_desc *cache = kobj_to_cache_desc(k);
-
-	return sprintf(buf, "%u\n", cache->associativity);
-}
-
-static struct kobj_attribute cache_assoc_attr =
-	__ATTR(ways_of_associativity, 0444, cache_assoc_show, NULL);
-
-struct cache_desc_info {
-	const char *type;
-	const char *size_prop;
-	const char *line_size_prop;
-	const char *nr_sets_prop;
-};
-
-/* PowerPC Processor binding says the [di]-cache-* must be equal on
- * unified caches, so just use d-cache properties. */
-static struct cache_desc_info ucache_info = {
-	.type = "Unified",
-	.size_prop = "d-cache-size",
-	.line_size_prop = "d-cache-line-size",
-	.nr_sets_prop = "d-cache-sets",
-};
-
-static struct cache_desc_info dcache_info = {
-	.type = "Data",
-	.size_prop = "d-cache-size",
-	.line_size_prop = "d-cache-line-size",
-	.nr_sets_prop = "d-cache-sets",
-};
-
-static struct cache_desc_info icache_info = {
-	.type = "Instruction",
-	.size_prop = "i-cache-size",
-	.line_size_prop = "i-cache-line-size",
-	.nr_sets_prop = "i-cache-sets",
-};
-
-static struct cache_desc * __cpuinit create_cache_desc(struct device_node *np, struct kobject *parent, int index, int level, struct cache_desc_info *info)
-{
-	const u32 *cache_line_size;
-	struct cache_desc *new;
-	const u32 *cache_size;
-	const u32 *nr_sets;
-	int rc;
-
-	new = kzalloc(sizeof(*new), GFP_KERNEL);
-	if (!new)
-		return NULL;
-
-	rc = kobject_init_and_add(&new->kobj, &cache_desc_type, parent,
-				  "index%d", index);
-	if (rc)
-		goto err;
-
-	/* type */
-	new->type = info->type;
-	rc = sysfs_create_file(&new->kobj, &cache_type_attr.attr);
-	WARN_ON(rc);
-
-	/* level */
-	new->level = level;
-	rc = sysfs_create_file(&new->kobj, &cache_level_attr.attr);
-	WARN_ON(rc);
-
-	/* size */
-	cache_size = of_get_property(np, info->size_prop, NULL);
-	if (cache_size) {
-		new->size = *cache_size / 1024;
-		rc = sysfs_create_file(&new->kobj,
-				       &cache_size_attr.attr);
-		WARN_ON(rc);
-	}
-
-	/* coherency_line_size */
-	cache_line_size = of_get_property(np, info->line_size_prop, NULL);
-	if (cache_line_size) {
-		new->line_size = *cache_line_size;
-		rc = sysfs_create_file(&new->kobj,
-				       &cache_line_size_attr.attr);
-		WARN_ON(rc);
-	}
-
-	/* number_of_sets */
-	nr_sets = of_get_property(np, info->nr_sets_prop, NULL);
-	if (nr_sets) {
-		new->nr_sets = *nr_sets;
-		rc = sysfs_create_file(&new->kobj,
-				       &cache_nr_sets_attr.attr);
-		WARN_ON(rc);
-	}
-
-	/* ways_of_associativity */
-	if (new->nr_sets == 1) {
-		/* fully associative */
-		new->associativity = 0;
-		goto create_assoc;
-	}
-
-	if (new->nr_sets && new->size && new->line_size) {
-		/* If we have values for all of these we can derive
-		 * the associativity. */
-		new->associativity =
-			((new->size * 1024) / new->nr_sets) / new->line_size;
-create_assoc:
-		rc = sysfs_create_file(&new->kobj,
-				       &cache_assoc_attr.attr);
-		WARN_ON(rc);
-	}
-
-	return new;
-err:
-	kfree(new);
-	return NULL;
-}
-
-static bool cache_is_unified(struct device_node *np)
-{
-	return of_get_property(np, "cache-unified", NULL);
-}
-
-static struct cache_desc * __cpuinit create_cache_index_info(struct device_node *np, struct kobject *parent, int index, int level)
-{
-	struct device_node *next_cache;
-	struct cache_desc *new, **end;
-
-	pr_debug("%s(node = %s, index = %d)\n", __func__, np->full_name, index);
-
-	if (cache_is_unified(np)) {
-		new = create_cache_desc(np, parent, index, level,
-					&ucache_info);
-	} else {
-		new = create_cache_desc(np, parent, index, level,
-					&dcache_info);
-		if (new) {
-			index++;
-			new->next = create_cache_desc(np, parent, index, level,
-						      &icache_info);
-		}
-	}
-	if (!new)
-		return NULL;
-
-	end = &new->next;
-	while (*end)
-		end = &(*end)->next;
-
-	next_cache = of_find_next_cache_node(np);
-	if (!next_cache)
-		goto out;
-
-	*end = create_cache_index_info(next_cache, parent, ++index, ++level);
-
-	of_node_put(next_cache);
-out:
-	return new;
-}
-
-static void __cpuinit create_cache_info(struct sys_device *sysdev)
-{
-	struct kobject *cache_toplevel;
-	struct device_node *np = NULL;
-	int cpu = sysdev->id;
-
-	cache_toplevel = kobject_create_and_add("cache", &sysdev->kobj);
-	if (!cache_toplevel)
-		return;
-	per_cpu(cache_toplevel, cpu) = cache_toplevel;
-	np = of_get_cpu_node(cpu, NULL);
-	if (np != NULL) {
-		per_cpu(cache_desc, cpu) =
-			create_cache_index_info(np, cache_toplevel, 0, 1);
-		of_node_put(np);
-	}
-	return;
-}
-
 static void __cpuinit register_cpu_online(unsigned int cpu)
 {
 	struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -684,25 +407,10 @@ static void __cpuinit register_cpu_online(unsigned int cpu)
 		sysdev_create_file(s, &attr_dscr);
 #endif /* CONFIG_PPC64 */
 
-	create_cache_info(s);
+	cacheinfo_cpu_online(cpu);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
-static void remove_cache_info(struct sys_device *sysdev)
-{
-	struct kobject *cache_toplevel;
-	struct cache_desc *cache_desc;
-	int cpu = sysdev->id;
-
-	cache_desc = per_cpu(cache_desc, cpu);
-	if (cache_desc != NULL)
-		kobject_put(&cache_desc->kobj);
-
-	cache_toplevel = per_cpu(cache_toplevel, cpu);
-	if (cache_toplevel != NULL)
-		kobject_put(cache_toplevel);
-}
-
 static void unregister_cpu_online(unsigned int cpu)
 {
 	struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -769,7 +477,7 @@ static void unregister_cpu_online(unsigned int cpu)
 		sysdev_remove_file(s, &attr_dscr);
 #endif /* CONFIG_PPC64 */
 
-	remove_cache_info(s);
+	cacheinfo_cpu_offline(cpu);
 }
 #endif /* CONFIG_HOTPLUG_CPU */