[RFC 3/4] ARM: topology: Update cpu_power according to DT information

Vincent Guittot
2012-06-12T12:02:55Z

Use cpu compatibility field and clock-frequency field of DT to
estimate the capacity of each core of the system

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
arch/arm/kernel/topology.c | 122 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 122 insertions(+)

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 2f85a64..0c2aee4 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -17,6 +17,7 @@
#include <linux/percpu.h>
#include <linux/node.h>
#include <linux/nodemask.h>
+#include <linux/of.h>
#include <linux/sched.h>

#include <asm/cputype.h>
@@ -47,6 +48,122 @@ void set_power_scale(unsigned int cpu, unsigned long power)
per_cpu(cpu_scale, cpu) = power;
}

+#ifdef CONFIG_OF
+struct cpu_efficiency {
+ const char *compatible;
+ unsigned long efficiency;
+};
+
+/*
+ * Table of relative efficiency of each processors
+ * The efficiency value must fit in 20bit. The final
+ * cpu_scale value must be in the range [1:2048[.
+ * Processors that are not defined in the table,
+ * use the default SCHED_POWER_SCALE value for cpu_scale.
+ */
+struct cpu_efficiency table_efficiency[] = {
+ {"arm,cortex-a15", 3891},
+ {"arm,cortex-a7", 2048},
+ {NULL, },
+};
+
+struct cpu_capacity {
+ unsigned long hwid;
+ unsigned long capacity;
+};
+
+struct cpu_capacity cpu_capacity[NR_CPUS];
+
+unsigned long middle_capacity = 1;
+
+static void __init parse_dt_topology(void)
+{
+ struct cpu_efficiency *cpu_eff;
+ struct device_node *cn = NULL;
+ unsigned long min_capacity = (unsigned long)(-1);
+ unsigned long max_capacity = 0;
+ unsigned long capacity = 0;
+ int cpu = 0;
+
+ while ((cn = of_find_node_by_type(cn, "cpu"))) {
+ const u32 *rate, *reg;
+ char *compatible;
+ int len;
+
+ if (cpu >= num_possible_cpus())
+ break;
+
+ compatible = of_get_property(cn, "compatible", &len);
+
+ for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)
+ if (of_device_is_compatible(cn, cpu_eff->compatible))
+ break;
+
+ if (cpu_eff->compatible == NULL)
+ continue;
+
+ rate = of_get_property(cn, "clock-frequency", &len);
+ if (!rate || len != 4) {
+ pr_err("%s missing clock-frequency property\n",
+ cn->full_name);
+ continue;
+ }
+
+ reg = of_get_property(cn, "reg", &len);
+ if (!reg || len != 4) {
+ pr_err("%s missing reg property\n", cn->full_name);
+ continue;
+ }
+
+ capacity = ((be32_to_cpup(rate)) >> 20)
+ * cpu_eff->efficiency;
+
+ /* Save min capacity of the system */
+ if (capacity < min_capacity)
+ min_capacity = capacity;
+
+ /* Save max capacity of the system */
+ if (capacity > max_capacity)
+ max_capacity = capacity;
+
+ cpu_capacity[cpu].capacity = capacity;
+ cpu_capacity[cpu++].hwid = be32_to_cpup(reg);
+ }
+
+ if (cpu < num_possible_cpus())
+ cpu_capacity[cpu].hwid = (unsigned long)(-1);
+
+ middle_capacity = (min_capacity + max_capacity) >> 11;
+}
+
+void update_cpu_power(unsigned int cpu, unsigned long hwid)
+{
+ unsigned int idx = 0;
+
+ /* look for the cpu's hwid in the cpu capacity table */
+ for (idx = 0; idx < num_possible_cpus(); idx++) {
+ if (cpu_capacity[idx].hwid == hwid)
+ break;
+
+ if (cpu_capacity[idx].hwid == -1)
+ return;
+ }
+
+ if (idx == num_possible_cpus())
+ return;
+
+ set_power_scale(cpu, cpu_capacity[idx].capacity / middle_capacity);
+
+ printk(KERN_INFO "CPU%u: update cpu_power %lu\n",
+ cpu, arch_scale_freq_power(NULL, cpu));
+}
+
+#else
+static inline void parse_dt_topology(void) {}
+static inline void update_cpu_power(unsigned int cpuid, unsigned int mpidr) {}
+#endif
+
+
/*
* cpu topology management
*/
@@ -60,6 +177,7 @@ void set_power_scale(unsigned int cpu, unsigned long power)
* These masks reflect the current use of the affinity levels.
* The affinity level can be up to 16 bits according to ARM ARM
*/
+#define MPIDR_HWID_BITMASK 0xFFFFFF

#define MPIDR_LEVEL0_MASK 0x3
#define MPIDR_LEVEL0_SHIFT 0
@@ -157,6 +275,8 @@ void store_cpu_topology(unsigned int cpuid)

update_siblings_masks(cpuid);

+ update_cpu_power(cpuid, mpidr & MPIDR_HWID_BITMASK);
+
printk(KERN_INFO "CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
cpuid, cpu_topology[cpuid].thread_id,
cpu_topology[cpuid].core_id,
@@ -184,4 +304,6 @@ void init_cpu_topology(void)
per_cpu(cpu_scale, cpu) = SCHED_POWER_SCALE;
}
smp_wmb();
+
+ parse_dt_topology();
}
--
1.7.9.5