linux-kernel - [PATCH 01/33] cacheinfo: Expose the code to generate a cache-id from a device

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Message-Id: <20250822153048.2287-2-james.morse@arm.com>
Date: Fri, 22 Aug 2025 15:29:42 +0000
From: James Morse <james.morse@....com>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-acpi@...r.kernel.org,
	devicetree@...r.kernel.org
Cc: James Morse <james.morse@....com>,
	shameerali.kolothum.thodi@...wei.com,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	carl@...amperecomputing.com,
	lcherian@...vell.com,
	bobo.shaobowang@...wei.com,
	tan.shaopeng@...itsu.com,
	baolin.wang@...ux.alibaba.com,
	Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>,
	peternewman@...gle.com,
	dfustini@...libre.com,
	amitsinght@...vell.com,
	David Hildenbrand <david@...hat.com>,
	Rex Nie <rex.nie@...uarmicro.com>,
	Dave Martin <dave.martin@....com>,
	Koba Ko <kobak@...dia.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	fenghuay@...dia.com,
	baisheng.gao@...soc.com,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Rob Herring <robh@...nel.org>,
	Rohit Mathew <rohit.mathew@....com>,
	Rafael Wysocki <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH 01/33] cacheinfo: Expose the code to generate a cache-id from a device_node

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@....com>
---
Changes since v1:
 * Renamed cache_of_get_id() cache_of_calculate_id().
---
 drivers/base/cacheinfo.c  | 19 +++++++++++++------
 include/linux/cacheinfo.h |  1 +
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 613410705a47..f6289d142ba9 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -207,11 +207,10 @@ 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;
+	unsigned long min_id = ~0UL;
 
 	for_each_of_cpu_node(cpu) {
 		u64 id = of_get_cpu_hwid(cpu, 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
-- 
2.20.1