[PATCH RFC 02/15] cacheinfo: Expose the code to generate a cache-id from a device_node

[Yin Li]

From: James Morse <james.morse@xxxxxxx>

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(). Even after device_initcall(),
the cache-id is only available if at least one CPU associated with
the cache is online.

Instead of making the driver wait, 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@xxxxxxx>
[ Yin Li: fix context conflicts in cacheinfo.c and cacheinfo.h; guard the
  cache_of_calculate_id() declaration with CONFIG_OF to prevent build
  errors when CONFIG_OF is not set ]
Signed-off-by: Yin Li <yin.li@xxxxxxxxxxxxxxxx>
---
 drivers/base/cacheinfo.c  | 17 ++++++++++++-----
 include/linux/cacheinfo.h |  3 +++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 9f9c72727a05..f75e7f64038b 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -226,8 +226,7 @@ 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)
+u32 cache_of_calculate_id(struct device_node *cache_node)
 {
 	struct device_node *cpu;
 	u32 min_id = ~0;
@@ -238,15 +237,23 @@ 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 ~0;
 		}
 
 		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)
+{
+	u32 id = cache_of_calculate_id(cache_node);
+
+	if (id != ~0) {
+		this_leaf->id = id;
 		this_leaf->attributes |= CACHE_ID;
 	}
 }
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index fc879ac4cc4f..c33bb3c8bd63 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -113,6 +113,9 @@ int acpi_get_cache_info(unsigned int cpu,
 #endif
 
 const struct attribute_group *cache_get_priv_group(struct cacheinfo *this_leaf);
+#ifdef CONFIG_OF
+u32 cache_of_calculate_id(struct device_node *np);
+#endif
 
 /*
  * Get the cacheinfo structure for the cache associated with @cpu at

-- 
2.34.1