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 device_initcall().

Expose the code that generates the cache-id. The parts of the MPAM
driver that run early can use this to set up the resctrl structures
before cacheinfo is ready in device_initcall().

Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v1:
  * Renamed cache_of_get_id() cache_of_calculate_id().
---
  drivers/base/cacheinfo.c  | 17 ++++++++++++-----
  include/linux/cacheinfo.h |  1 +
  2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 613410705a47..0fdd6358ee73 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c

@@ -207,8 +207,7 @@ static bool match_cache_node(struct device_node *cpu,
  #define arch_compact_of_hwid(_x)	(_x)
  #endif
  
-static void cache_of_set_id(struct cacheinfo *this_leaf,
-			    struct device_node *cache_node)
+unsigned long cache_of_calculate_id(struct device_node *cache_node)
  {
  	struct device_node *cpu;
  	u32 min_id = ~0;

@@ -219,15 +218,23 @@ static void cache_of_set_id(struct cacheinfo *this_leaf,
  		id = arch_compact_of_hwid(id);
  		if (FIELD_GET(GENMASK_ULL(63, 32), id)) {
  			of_node_put(cpu);
-			return;
+			return ~0UL;
  		}
  
  		if (match_cache_node(cpu, cache_node))
  			min_id = min(min_id, id);
  	}
  
-	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 *cache_node)
+{
+	unsigned long id = cache_of_calculate_id(cache_node);
+
+	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..2dcbb69139e9 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_calculate_id(struct device_node *np);
  
  /*
   * Get the cacheinfo structure for the cache associated with @cpu at