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authorMorten Rasmussen <Morten.Rasmussen@arm.com>2012-09-14 14:38:13 +0100
committerViresh Kumar <viresh.kumar@linaro.org>2013-01-04 12:25:54 +0530
commitd6f82b0bc04ec0ef02cc7f3edb6db8dbc3fe0550 (patch)
tree7021b42adadad0e949779815a9298e86ef1dd9ba
parent1cdd8b72f8fa52af7dc33d00c338de65afc1c8bb (diff)
downloadvexpress-lsk-d6f82b0bc04ec0ef02cc7f3edb6db8dbc3fe0550.tar.gz
ARM: sched: Use device-tree to provide fast/slow CPU list for HMP
We can't rely on Kconfig options to set the fast and slow CPU lists for HMP scheduling if we want a single kernel binary to support multiple devices with different CPU topology. E.g. TC2 (ARM's Test-Chip-2 big.LITTLE system), Fast Models, or even non big.LITTLE devices. This patch adds the function arch_get_fast_and_slow_cpus() to generate the lists at run-time by parsing the CPU nodes in device-tree; it assumes slow cores are A7s and everything else is fast. The function still supports the old Kconfig options as this is useful for testing the HMP scheduler on devices without big.LITTLE. This patch is reuse of a patch by Jon Medhurst <tixy@linaro.org> with a few bits left out. Signed-off-by: Morten Rasmussen <Morten.Rasmussen@arm.com>
-rw-r--r--arch/arm/Kconfig4
-rw-r--r--arch/arm/kernel/topology.c69
2 files changed, 72 insertions, 1 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index cad806996ba..641f261d4af 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1596,13 +1596,15 @@ config HMP_FAST_CPU_MASK
string "HMP scheduler fast CPU mask"
depends on SCHED_HMP
help
- Specify the cpuids of the fast CPUs in the system as a list string,
+ Leave empty to use device tree information.
+ Specify the cpuids of the fast CPUs in the system as a list string,
e.g. cpuid 0+1 should be specified as 0-1.
config HMP_SLOW_CPU_MASK
string "HMP scheduler slow CPU mask"
depends on SCHED_HMP
help
+ Leave empty to use device tree information.
Specify the cpuids of the slow CPUs in the system as a list string,
e.g. cpuid 0+1 should be specified as 0-1.
diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 79282ebcd93..eac7424d372 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -287,6 +287,75 @@ void store_cpu_topology(unsigned int cpuid)
cpu_topology[cpuid].socket_id, mpidr);
}
+
+#ifdef CONFIG_SCHED_HMP
+
+static const char * const little_cores[] = {
+ "arm,cortex-a7",
+ NULL,
+};
+
+static bool is_little_cpu(struct device_node *cn)
+{
+ const char * const *lc;
+ for (lc = little_cores; *lc; lc++)
+ if (of_device_is_compatible(cn, *lc))
+ return true;
+ return false;
+}
+
+void __init arch_get_fast_and_slow_cpus(struct cpumask *fast,
+ struct cpumask *slow)
+{
+ struct device_node *cn = NULL;
+ int cpu = 0;
+
+ cpumask_clear(fast);
+ cpumask_clear(slow);
+
+ /*
+ * Use the config options if they are given. This helps testing
+ * HMP scheduling on systems without a big.LITTLE architecture.
+ */
+ if (strlen(CONFIG_HMP_FAST_CPU_MASK) && strlen(CONFIG_HMP_SLOW_CPU_MASK)) {
+ if (cpulist_parse(CONFIG_HMP_FAST_CPU_MASK, fast))
+ WARN(1, "Failed to parse HMP fast cpu mask!\n");
+ if (cpulist_parse(CONFIG_HMP_SLOW_CPU_MASK, slow))
+ WARN(1, "Failed to parse HMP slow cpu mask!\n");
+ return;
+ }
+
+ /*
+ * Else, parse device tree for little cores.
+ */
+ while ((cn = of_find_node_by_type(cn, "cpu"))) {
+
+ if (cpu >= num_possible_cpus())
+ break;
+
+ if (is_little_cpu(cn))
+ cpumask_set_cpu(cpu, slow);
+ else
+ cpumask_set_cpu(cpu, fast);
+
+ cpu++;
+ }
+
+ if (!cpumask_empty(fast) && !cpumask_empty(slow))
+ return;
+
+ /*
+ * We didn't find both big and little cores so let's call all cores
+ * fast as this will keep the system running, with all cores being
+ * treated equal.
+ */
+ cpumask_setall(fast);
+ cpumask_clear(slow);
+}
+
+#endif /* CONFIG_SCHED_HMP */
+
+
/*
* init_cpu_topology is called at boot when only one cpu is running
* which prevent simultaneous write access to cpu_topology array