linux-kernel - [PATCH v2 7/8] of: base: add support to get the device node for the CPU's last level cache

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Date:   Wed, 18 May 2022 10:33:24 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Atish Patra <atishp@...shpatra.org>, linux-kernel@...r.kernel.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Atish Patra <atishp@...osinc.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, Rob Herring <robh+dt@...nel.org>
Subject: [PATCH v2 7/8] of: base: add support to get the device node for the CPU's last level cache

It is useful to have helper function just to get the pointer to the device
node of the last level cache for a given logical cpu. It can be used as
unique firmware identifier for the last level cache.

This is useful to obtain the cpumask/cpumap of all the CPUs sharing the last
level cache using the device node pointer as unique identifier for the last
level cache.

Cc: Rob Herring <robh+dt@...nel.org>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/of/base.c  | 33 +++++++++++++++++++++++++--------
 include/linux/of.h |  1 +
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index d4f98c8469ed..0b6a8c3f9a85 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2072,17 +2072,17 @@ struct device_node *of_find_next_cache_node(const struct device_node *np)
 }
 
 /**
- * of_find_last_cache_level - Find the level at which the last cache is
- * 		present for the given logical cpu
+ * of_find_last_level_cache_node - Find the device node at which the last
+ *		cache is present for the given logical cpu
  *
- * @cpu: cpu number(logical index) for which the last cache level is needed
+ * @cpu: cpu number(logical index) for which the last cache level's device
+ * node is needed
  *
- * Return: The the level at which the last cache is present. It is exactly
- * same as  the total number of cache levels for the given logical cpu.
+ * Return: The device node corresponding to the last cache for the  given
+ * logical cpu
  */
-int of_find_last_cache_level(unsigned int cpu)
+struct device_node *of_find_last_level_cache_node(unsigned int cpu)
 {
-	u32 cache_level = 0;
 	struct device_node *prev = NULL, *np = of_cpu_device_node_get(cpu);
 
 	while (np) {
@@ -2091,7 +2091,24 @@ int of_find_last_cache_level(unsigned int cpu)
 		np = of_find_next_cache_node(np);
 	}
 
-	of_property_read_u32(prev, "cache-level", &cache_level);
+	return prev;
+}
+
+/**
+ * of_find_last_cache_level - Find the level at which the last cache is
+ *		present for the given logical cpu
+ *
+ * @cpu: cpu number(logical index) for which the last cache level is needed
+ *
+ * Return: The level at which the last cache is present. It is exactly
+ * same as  the total number of cache levels for the given logical cpu.
+ */
+int of_find_last_cache_level(unsigned int cpu)
+{
+	u32 cache_level = 0;
+	struct device_node *np = of_find_last_level_cache_node(cpu);
+
+	of_property_read_u32(np, "cache-level", &cache_level);
 
 	return cache_level;
 }
diff --git a/include/linux/of.h b/include/linux/of.h
index 04971e85fbc9..ca0384cf08a3 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -297,6 +297,7 @@ extern struct device_node *of_get_child_by_name(const struct device_node *node,
 
 /* cache lookup */
 extern struct device_node *of_find_next_cache_node(const struct device_node *);
+extern struct device_node *of_find_last_level_cache_node(unsigned int cpu);
 extern int of_find_last_cache_level(unsigned int cpu);
 extern struct device_node *of_find_node_with_property(
 	struct device_node *from, const char *prop_name);
-- 
2.36.1