linux-kernel - [PATCH V2 1/2] arch_topology: support for parsing cache topology from DT

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Message-Id: <1650628289-67716-2-git-send-email-wangqing@vivo.com>
Date:   Fri, 22 Apr 2022 04:51:25 -0700
From:   Qing Wang <wangqing@...o.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     vincent.guittot@...aro.org, dietmar.eggemann@....com,
        Wang Qing <wangqing@...o.com>
Subject: [PATCH V2 1/2] arch_topology: support for parsing cache topology from DT

From: Wang Qing <wangqing@...o.com>

When ACPI is not enabled, we can get cache topolopy from DT like:
*		cpu0: cpu@000 {
*			next-level-cache = <&L2_1>;
*			L2_1: l2-cache {
* 				compatible = "cache";
*				next-level-cache = <&L3_1>;
* 			};
*			L3_1: l3-cache {
* 				compatible = "cache";
* 			};
*		};
*
*		cpu1: cpu@001 {
*			next-level-cache = <&L2_1>;
*		};
*		...
*		};
cache_topology[] hold the pointer describing by "next-level-cache", 
which can describe the cache topology of every level.

MAX_CACHE_LEVEL is strictly corresponding to the cache level from L2.

V2:
make function name more sense

Signed-off-by: Wang Qing <wangqing@...o.com>
---
 drivers/base/arch_topology.c  | 47 ++++++++++++++++++++++++++++++++++-
 include/linux/arch_topology.h |  3 +++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 1d6636ebaac5..46e84ce2ec0c 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -480,8 +480,10 @@ static int __init get_cpu_for_node(struct device_node *node)
 		return -1;
 
 	cpu = of_cpu_node_to_id(cpu_node);
-	if (cpu >= 0)
+	if (cpu >= 0) {
 		topology_parse_cpu_capacity(cpu_node, cpu);
+		topology_parse_cpu_caches(cpu_node, cpu);
+	}
 	else
 		pr_info("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
 			cpu_node, cpumask_pr_args(cpu_possible_mask));
@@ -647,6 +649,49 @@ static int __init parse_dt_topology(void)
 }
 #endif
 
+/*
+ * cpu cache topology table
+ */
+#define MAX_CACHE_LEVEL 7
+static struct device_node *cache_topology[NR_CPUS][MAX_CACHE_LEVEL];
+
+void topology_parse_cpu_caches(struct device_node *cpu_node, int cpu)
+{
+	struct device_node *node_cache = cpu_node;
+	int level = 0;
+
+	while (level < MAX_CACHE_LEVEL) {
+		node_cache = of_parse_phandle(node_cache, "next-level-cache", 0);
+		if (!node_cache)
+			break;
+
+		cache_topology[cpu][level++] = node_cache;
+	}
+}
+
+/*
+ * find the largest subset of the shared cache in the range of cpu_mask
+ */
+void find_subset_of_share_cache(const struct cpumask *cpu_mask, int cpu,
+								 struct cpumask *sc_mask)
+{
+	int cache_level, cpu_id;
+
+	for (cache_level = MAX_CACHE_LEVEL - 1; cache_level >= 0; cache_level--) {
+		if (!cache_topology[cpu][cache_level])
+			continue;
+
+		cpumask_clear(sc_mask);
+		for (cpu_id = 0; cpu_id < NR_CPUS; cpu_id++) {
+			if (cache_topology[cpu][cache_level] == cache_topology[cpu_id][cache_level])
+				cpumask_set_cpu(cpu_id, sc_mask);
+		}
+
+		if (cpumask_subset(sc_mask, cpu_mask))
+			break;
+	}
+}
+
 /*
  * cpu topology table
  */
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 58cbe18d825c..c6ed727e453c 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -93,6 +93,9 @@ void update_siblings_masks(unsigned int cpu);
 void remove_cpu_topology(unsigned int cpuid);
 void reset_cpu_topology(void);
 int parse_acpi_topology(void);
+void topology_parse_cpu_caches(struct device_node *cpu_node, int cpu);
+void find_subset_of_share_cache(const struct cpumask *cpu_mask, int cpu,
+								 struct cpumask *sc_mask);
 #endif
 
 #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
-- 
2.7.4