linux-kernel - [PATCH V2] arch_topology: support parsing cluster

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Date:   Wed, 11 May 2022 02:52:56 -0700
From:   Qing Wang <wangqing@...o.com>
To:     Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Cc:     dietmar.eggemann@....com, Wang Qing <wangqing@...o.com>
Subject: [PATCH V2] arch_topology: support parsing cluster_id from DT

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

Use nested cluster structures in DT to support describing multi-level
cluster topologies and increase the parsing of nested cluster.

Notice: the clusters describing in DT currently are not physical
boundaries, since changing "cluster" to "socket" is too involved and error
prone, this patch will not have any effect on one-level cluster topo, but
can support the mutil-level cluster topo to support CLUSTER_SCHED.

Signed-off-by: Wang Qing <wangqing@...o.com>
---
 drivers/base/arch_topology.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 1d6636ebaac5..5a407cff0ab1 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -491,7 +491,7 @@ static int __init get_cpu_for_node(struct device_node *node)
 }
 
 static int __init parse_core(struct device_node *core, int package_id,
-			     int core_id)
+			     int cluster_id, int core_id)
 {
 	char name[20];
 	bool leaf = true;
@@ -507,6 +507,7 @@ static int __init parse_core(struct device_node *core, int package_id,
 			cpu = get_cpu_for_node(t);
 			if (cpu >= 0) {
 				cpu_topology[cpu].package_id = package_id;
+				cpu_topology[cpu].cluster_id = cluster_id;
 				cpu_topology[cpu].core_id = core_id;
 				cpu_topology[cpu].thread_id = i;
 			} else if (cpu != -ENODEV) {
@@ -528,6 +529,7 @@ static int __init parse_core(struct device_node *core, int package_id,
 		}
 
 		cpu_topology[cpu].package_id = package_id;
+		cpu_topology[cpu].cluster_id = cluster_id;
 		cpu_topology[cpu].core_id = core_id;
 	} else if (leaf && cpu != -ENODEV) {
 		pr_err("%pOF: Can't get CPU for leaf core\n", core);
@@ -544,13 +546,15 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
 	bool has_cores = false;
 	struct device_node *c;
 	static int package_id __initdata;
+	static int cluster_id __initdata;
 	int core_id = 0;
 	int i, ret;
 
 	/*
-	 * First check for child clusters; we currently ignore any
-	 * information about the nesting of clusters and present the
-	 * scheduler with a flat list of them.
+	 * nesting of clusters :
+	 * level 1:  package_id
+	 * level 2:  cluster_id
+	 * level 3+: ignore
 	 */
 	i = 0;
 	do {
@@ -559,6 +563,14 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
 		if (c) {
 			leaf = false;
 			ret = parse_cluster(c, depth + 1);
+			if (depth == 0) {
+				package_id++;
+				cluster_id = 0;
+			} else if (depth == 1)
+				cluster_id++;
+			else
+				pr_err("Ignore nested clusters with more than two levels!\n");
+
 			of_node_put(c);
 			if (ret != 0)
 				return ret;
@@ -582,7 +594,8 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
 			}
 
 			if (leaf) {
-				ret = parse_core(c, package_id, core_id++);
+				ret = parse_core(c, package_id, (depth == 2)?cluster_id : -1,
+					       core_id++);
 			} else {
 				pr_err("%pOF: Non-leaf cluster with core %s\n",
 				       cluster, name);
@@ -599,9 +612,6 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
 	if (leaf && !has_cores)
 		pr_warn("%pOF: empty cluster\n", cluster);
 
-	if (leaf)
-		package_id++;
-
 	return 0;
 }
 
-- 
2.7.4