linux-kernel - [PATCH v4 1/5] ARM: topology: Add arch_scale_freq

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Date:	Mon,  9 Jul 2012 11:27:02 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linaro-dev@...ts.linaro.org, devicetree-discuss@...ts.ozlabs.org
Cc:	linux@....linux.org.uk, a.p.zijlstra@...llo.nl,
	grant.likely@...retlab.ca, rob.herring@...xeda.com,
	yong.zhang0@...il.com, namhyung@...nel.org,
	jean.pihet@...oldbits.com,
	Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH v4 1/5] ARM: topology: Add arch_scale_freq_power function

Add infrastructure to be able to modify the cpu_power of each core

Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
Reviewed-by: Namhyung Kim <namhyung@...nel.org>
---
 arch/arm/kernel/topology.c |   38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 8200dea..51f23b3 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -22,6 +22,37 @@
 #include <asm/cputype.h>
 #include <asm/topology.h>
 
+/*
+ * cpu power scale management
+ */
+
+/*
+ * cpu power table
+ * This per cpu data structure describes the relative capacity of each core.
+ * On a heteregenous system, cores don't have the same computation capacity
+ * and we reflect that difference in the cpu_power field so the scheduler can
+ * take this difference into account during load balance. A per cpu structure
+ * is preferred because each CPU updates its own cpu_power field during the
+ * load balance except for idle cores. One idle core is selected to run the
+ * rebalance_domains for all idle cores and the cpu_power can be updated
+ * during this sequence.
+ */
+static DEFINE_PER_CPU(unsigned long, cpu_scale);
+
+unsigned long arch_scale_freq_power(struct sched_domain *sd, int cpu)
+{
+	return per_cpu(cpu_scale, cpu);
+}
+
+static void set_power_scale(unsigned int cpu, unsigned long power)
+{
+	per_cpu(cpu_scale, cpu) = power;
+}
+
+/*
+ * cpu topology management
+ */
+
 #define MPIDR_SMP_BITMASK (0x3 << 30)
 #define MPIDR_SMP_VALUE (0x2 << 30)
 
@@ -41,6 +72,9 @@
 #define MPIDR_LEVEL2_MASK 0xFF
 #define MPIDR_LEVEL2_SHIFT 16
 
+/*
+ * cpu topology table
+ */
 struct cputopo_arm cpu_topology[NR_CPUS];
 
 const struct cpumask *cpu_coregroup_mask(int cpu)
@@ -134,7 +168,7 @@ void init_cpu_topology(void)
 {
 	unsigned int cpu;
 
-	/* init core mask */
+	/* init core mask and power*/
 	for_each_possible_cpu(cpu) {
 		struct cputopo_arm *cpu_topo = &(cpu_topology[cpu]);
 
@@ -143,6 +177,8 @@ void init_cpu_topology(void)
 		cpu_topo->socket_id = -1;
 		cpumask_clear(&cpu_topo->core_sibling);
 		cpumask_clear(&cpu_topo->thread_sibling);
+
+		set_power_scale(cpu, SCHED_POWER_SCALE);
 	}
 	smp_wmb();
 }
-- 
1.7.9.5

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