[PATCH 2/4] arm64: topology: Add support for topology DT bindings
Lorenzo Pieralisi
lorenzo.pieralisi at arm.com
Thu Apr 24 07:48:46 PDT 2014
On Tue, Apr 22, 2014 at 09:21:16PM +0100, Mark Brown wrote:
> From: Mark Brown <broonie at linaro.org>
>
> Add support for parsing the explicit topology bindings to discover the
> topology of the system.
>
> Since it is not currently clear how to map multi-level clusters for the
> scheduler all leaf clusters are presented to the scheduler at the same
> level. This should be enough to provide good support for current systems.
>
> Signed-off-by: Mark Brown <broonie at linaro.org>
> ---
> arch/arm64/kernel/topology.c | 203 +++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 195 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> index ff662b23af5f..a326f5b37546 100644
> --- a/arch/arm64/kernel/topology.c
> +++ b/arch/arm64/kernel/topology.c
> @@ -17,10 +17,191 @@
> #include <linux/percpu.h>
> #include <linux/node.h>
> #include <linux/nodemask.h>
> +#include <linux/of.h>
> #include <linux/sched.h>
>
> #include <asm/topology.h>
>
> +static int __init get_cpu_for_node(struct device_node *node)
> +{
> + struct device_node *cpu_node;
> + int cpu;
> +
> + cpu_node = of_parse_phandle(node, "cpu", 0);
> + if (!cpu_node)
> + return -1;
> +
> + for_each_possible_cpu(cpu)
> + if (of_get_cpu_node(cpu, NULL) == cpu_node) {
> + of_node_put(cpu_node);
> + return cpu;
> + }
> +
> + pr_crit("Unable to find CPU node for %s\n", cpu_node->full_name);
> +
> + of_node_put(cpu_node);
> + return -1;
> +}
> +
> +static int __init parse_core(struct device_node *core, int cluster_id,
> + int core_id)
> +{
> + char name[10];
> + bool leaf = true;
> + int i = 0;
> + int cpu;
> + struct device_node *t;
> +
> + do {
> + snprintf(name, sizeof(name), "thread%d", i);
> + t = of_get_child_by_name(core, name);
> + if (t) {
> + leaf = false;
> + cpu = get_cpu_for_node(t);
> + if (cpu >= 0) {
> + cpu_topology[cpu].cluster_id = cluster_id;
> + cpu_topology[cpu].core_id = core_id;
> + cpu_topology[cpu].thread_id = i;
> + } else {
> + pr_err("%s: Can't get CPU for thread\n",
> + t->full_name);
> + of_node_put(t);
> + return -EINVAL;
> + }
> + of_node_put(t);
> + }
> + i++;
> + } while (t);
> +
> + cpu = get_cpu_for_node(core);
> + if (cpu >= 0) {
> + if (!leaf) {
> + pr_err("%s: Core has both threads and CPU\n",
> + core->full_name);
> + return -EINVAL;
> + }
> +
> + cpu_topology[cpu].cluster_id = cluster_id;
> + cpu_topology[cpu].core_id = core_id;
> + } else if (leaf) {
> + pr_err("%s: Can't get CPU for leaf core\n", core->full_name);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int __init parse_cluster(struct device_node *cluster, int depth)
> +{
> + char name[10];
> + bool leaf = true;
> + bool has_cores = false;
> + struct device_node *c;
> + 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.
> + */
> + i = 0;
> + do {
> + snprintf(name, sizeof(name), "cluster%d", i);
> + c = of_get_child_by_name(cluster, name);
> + if (c) {
> + leaf = false;
> + ret = parse_cluster(c, depth + 1);
> + of_node_put(c);
> + if (ret != 0)
> + return ret;
> + }
> + i++;
> + } while (c);
> +
> + /* Now check for cores */
> + i = 0;
> + do {
> + snprintf(name, sizeof(name), "core%d", i);
> + c = of_get_child_by_name(cluster, name);
> + if (c) {
> + has_cores = true;
> +
> + if (depth == 0) {
> + pr_err("%s: cpu-map children should be clusters\n",
> + c->full_name);
> + of_node_put(c);
> + return -EINVAL;
> + }
> +
> + if (leaf) {
> + ret = parse_core(c, cluster_id, core_id++);
> + } else {
> + pr_err("%s: Non-leaf cluster with core %s\n",
> + cluster->full_name, name);
> + ret = -EINVAL;
> + }
> +
> + of_node_put(c);
> + if (ret != 0)
> + return ret;
> + }
> + i++;
> + } while (c);
> +
> + if (leaf && !has_cores)
> + pr_warn("%s: empty cluster\n", cluster->full_name);
> +
> + if (leaf)
> + cluster_id++;
> +
> + return 0;
> +}
> +
> +static int __init parse_dt_topology(void)
> +{
> + struct device_node *cn, *map;
> + int ret = 0;
> + int cpu;
> +
> + cn = of_find_node_by_path("/cpus");
> + if (!cn) {
> + pr_err("No CPU information found in DT\n");
> + return 0;
> + }
> +
> + /*
> + * When topology is provided cpu-map is essentially a root
> + * cluster with restricted subnodes.
> + */
> + map = of_get_child_by_name(cn, "cpu-map");
> + if (!map)
> + goto out;
> +
> + ret = parse_cluster(map, 0);
> + if (ret != 0)
> + goto out_map;
> +
> + /*
> + * Check that all cores are in the topology; the SMP code will
> + * only mark cores described in the DT as possible.
> + */
> + for_each_possible_cpu(cpu) {
> + if (cpu_topology[cpu].cluster_id == -1) {
> + pr_err("CPU%d: No topology information specified\n",
> + cpu);
> + ret = -EINVAL;
> + }
> + }
> +
> +out_map:
> + of_node_put(map);
> +out:
> + of_node_put(cn);
> + return ret;
> +}
> +
> /*
> * cpu topology table
> */
> @@ -39,8 +220,7 @@ static void update_siblings_masks(unsigned int cpuid)
>
> if (cpuid_topo->cluster_id == -1) {
> /*
> - * DT does not contain topology information for this cpu
> - * reset it to default behaviour
> + * DT does not contain topology information for this cpu.
> */
> pr_debug("CPU%u: No topology information configured\n", cpuid);
> return;
> @@ -71,15 +251,10 @@ void store_cpu_topology(unsigned int cpuid)
> update_siblings_masks(cpuid);
> }
>
> -/*
> - * init_cpu_topology is called at boot when only one cpu is running
> - * which prevent simultaneous write access to cpu_topology array
> - */
> -void __init init_cpu_topology(void)
> +static void __init reset_cpu_topology(void)
> {
> unsigned int cpu;
>
> - /* init core mask and power*/
> for_each_possible_cpu(cpu) {
> struct cpu_topology *cpu_topo = &cpu_topology[cpu];
>
> @@ -93,3 +268,15 @@ void __init init_cpu_topology(void)
> cpumask_set_cpu(cpu, &cpu_topo->thread_sibling);
> }
> }
> +
> +void __init init_cpu_topology(void)
> +{
> + reset_cpu_topology();
> +
> + /*
> + * Discard anything that was parsed if we hit an error so we
> + * don't use partial information.
> + */
> + if (parse_dt_topology())
> + reset_cpu_topology();
> +}
I tested it and tried to clobber it a bit with some DT changes, it seems
fine.
Apart from an ultra-minor decoration change (attached):
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
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