[PATCH 4/5] cacheinfo: Expose the code to generate a cache-id from a device_node

[James Morse <james.morse@arm.com>]

The MPAM driver identifies caches by id for use with resctrl. It
needs to know the cache-id when probe-ing, but the value isn't set
in cacheinfo until the corresponding CPU comes online.

Expose the code that generates the cache-id. This allows the MPAM
driver to determine the properties of the caches without waiting
for all CPUs to come online.

Signed-off-by: James Morse <james.morse@arm.com>
---
 drivers/base/cacheinfo.c  | 15 +++++++++++----
 include/linux/cacheinfo.h |  1 +
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index d8e5b4c7156c..6316d80abab8 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -188,7 +188,7 @@ static bool cache_node_is_unified(struct cacheinfo *this_leaf,
 #define arch_compact_of_hwid(_x)	(_x)
 #endif
 
-static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
+unsigned long cache_of_get_id(struct device_node *np)
 {
 	struct device_node *cpu;
 	u32 min_id = ~0;
@@ -200,7 +200,7 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
 		id = arch_compact_of_hwid(id);
 		if (FIELD_GET(GENMASK_ULL(63, 32), id)) {
 			of_node_put(cpu);
-			return;
+			return ~0UL;
 		}
 		while (1) {
 			if (!cache_node)
@@ -214,8 +214,15 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
 		}
 	}
 
-	if (min_id != ~0) {
-		this_leaf->id = min_id;
+	return min_id;
+}
+
+static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
+{
+	unsigned long id = cache_of_get_id(np);
+
+	if (id != ~0UL) {
+		this_leaf->id = id;
 		this_leaf->attributes |= CACHE_ID;
 	}
 }
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index c8f4f0a0b874..9c959caf8af8 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -112,6 +112,7 @@ int acpi_get_cache_info(unsigned int cpu,
 #endif
 
 const struct attribute_group *cache_get_priv_group(struct cacheinfo *this_leaf);
+unsigned long cache_of_get_id(struct device_node *np);
 
 /*
  * Get the cacheinfo structure for the cache associated with @cpu at
-- 
2.39.5