6 files changed, 218 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 3269576dbfa8..c208fd97c180 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1393,6 +1393,31 @@ config SMP_ON_UP
 
           If you don't know what to do here, say Y.
 
+config ARM_CPU_TOPOLOGY
+        bool "Support cpu topology definition"
+        depends on SMP && CPU_V7
+        default y
+        help
+          Support ARM cpu topology definition. The MPIDR register defines
+          affinity between processors which is then used to describe the cpu
+          topology of an ARM System.
+
+config SCHED_MC
+        bool "Multi-core scheduler support"
+        depends on ARM_CPU_TOPOLOGY
+        help
+          Multi-core scheduler support improves the CPU scheduler's decision
+          making when dealing with multi-core CPU chips at a cost of slightly
+          increased overhead in some places. If unsure say N here.
+
+config SCHED_SMT
+        bool "SMT scheduler support"
+        depends on ARM_CPU_TOPOLOGY
+        help
+          Improves the CPU scheduler's decision making when dealing with
+          MultiThreading at a cost of slightly increased overhead in some
+          places. If unsure say N here.
+
 config HAVE_ARM_SCU
         bool
         help
diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h
index cd4458f64171..cb47d28cbe1f 100644
--- a/arch/arm/include/asm/cputype.h
+++ b/arch/arm/include/asm/cputype.h
@@ -8,6 +8,7 @@
 #define CPUID_CACHETYPE 1
 #define CPUID_TCM       2
 #define CPUID_TLBTYPE   3
+#define CPUID_MPIDR     5
 
 #define CPUID_EXT_PFR0  "c1, 0"
 #define CPUID_EXT_PFR1  "c1, 1"
@@ -70,6 +71,11 @@ static inline unsigned int __attribute_const__ read_cpuid_tcmstatus(void)
         return read_cpuid(CPUID_TCM);
 }
 
+static inline unsigned int __attribute_const__ read_cpuid_mpidr(void)
+{
+        return read_cpuid(CPUID_MPIDR);
+}
+
 /*
  * Intel's XScale3 core supports some v6 features (supersections, L2)
  * but advertises itself as v5 as it does not support the v6 ISA.  For
diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
index accbd7cad9b5..a7e457ed27c3 100644
--- a/arch/arm/include/asm/topology.h
+++ b/arch/arm/include/asm/topology.h
@@ -1,6 +1,39 @@
 #ifndef _ASM_ARM_TOPOLOGY_H
 #define _ASM_ARM_TOPOLOGY_H
 
+#ifdef CONFIG_ARM_CPU_TOPOLOGY
+
+#include <linux/cpumask.h>
+
+struct cputopo_arm {
+        int thread_id;
+        int core_id;
+        int socket_id;
+        cpumask_t thread_sibling;
+        cpumask_t core_sibling;
+};
+
+extern struct cputopo_arm cpu_topology[NR_CPUS];
+
+#define topology_physical_package_id(cpu)       (cpu_topology[cpu].socket_id)
+#define topology_core_id(cpu)           (cpu_topology[cpu].core_id)
+#define topology_core_cpumask(cpu)      (&cpu_topology[cpu].core_sibling)
+#define topology_thread_cpumask(cpu)    (&cpu_topology[cpu].thread_sibling)
+
+#define mc_capable()    (cpu_topology[0].socket_id != -1)
+#define smt_capable()   (cpu_topology[0].thread_id != -1)
+
+void init_cpu_topology(void);
+void store_cpu_topology(unsigned int cpuid);
+const struct cpumask *cpu_coregroup_mask(unsigned int cpu);
+
+#else
+
+static inline void init_cpu_topology(void) { }
+static inline void store_cpu_topology(unsigned int cpuid) { }
+
+#endif
+
 #include <asm-generic/topology.h>
 
 #endif /* _ASM_ARM_TOPOLOGY_H */
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index f7887dc53c1f..c687bceba7da 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -66,6 +66,7 @@ obj-$(CONFIG_IWMMXT)		+= iwmmxt.o
 obj-$(CONFIG_CPU_HAS_PMU)       += pmu.o
 obj-$(CONFIG_HW_PERF_EVENTS)    += perf_event.o
 AFLAGS_iwmmxt.o                 := -Wa,-mcpu=iwmmxt
+obj-$(CONFIG_ARM_CPU_TOPOLOGY)  += topology.o
 
 ifneq ($(CONFIG_ARCH_EBSA110),y)
   obj-y         += io.o
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index d88ff0230e82..62775c5c5ba0 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -31,6 +31,7 @@
 #include <asm/cacheflush.h>
 #include <asm/cpu.h>
 #include <asm/cputype.h>
+#include <asm/topology.h>
 #include <asm/mmu_context.h>
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -268,6 +269,8 @@ static void __cpuinit smp_store_cpu_info(unsigned int cpuid)
         struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpuid);
 
         cpu_info->loops_per_jiffy = loops_per_jiffy;
+
+        store_cpu_topology(cpuid);
 }
 
 /*
@@ -358,6 +361,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 {
         unsigned int ncores = num_possible_cpus();
 
+        init_cpu_topology();
+
         smp_store_cpu_info(smp_processor_id());
 
         /*
diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
new file mode 100644
index 000000000000..1040c00405d0
--- /dev/null
+++ b/arch/arm/kernel/topology.c
@@ -0,0 +1,148 @@
+/*
+ * arch/arm/kernel/topology.c
+ *
+ * Copyright (C) 2011 Linaro Limited.
+ * Written by: Vincent Guittot
+ *
+ * based on arch/sh/kernel/topology.c
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/init.h>
+#include <linux/percpu.h>
+#include <linux/node.h>
+#include <linux/nodemask.h>
+#include <linux/sched.h>
+
+#include <asm/cputype.h>
+#include <asm/topology.h>
+
+#define MPIDR_SMP_BITMASK (0x3 << 30)
+#define MPIDR_SMP_VALUE (0x2 << 30)
+
+#define MPIDR_MT_BITMASK (0x1 << 24)
+
+/*
+ * 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_LEVEL0_MASK 0x3
+#define MPIDR_LEVEL0_SHIFT 0
+
+#define MPIDR_LEVEL1_MASK 0xF
+#define MPIDR_LEVEL1_SHIFT 8
+
+#define MPIDR_LEVEL2_MASK 0xFF
+#define MPIDR_LEVEL2_SHIFT 16
+
+struct cputopo_arm cpu_topology[NR_CPUS];
+
+const struct cpumask *cpu_coregroup_mask(unsigned int cpu)
+{
+        return &cpu_topology[cpu].core_sibling;
+}
+
+/*
+ * store_cpu_topology is called at boot when only one cpu is running
+ * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
+ * which prevents simultaneous write access to cpu_topology array
+ */
+void store_cpu_topology(unsigned int cpuid)
+{
+        struct cputopo_arm *cpuid_topo = &cpu_topology[cpuid];
+        unsigned int mpidr;
+        unsigned int cpu;
+
+        /* If the cpu topology has been already set, just return */
+        if (cpuid_topo->core_id != -1)
+                return;
+
+        mpidr = read_cpuid_mpidr();
+
+        /* create cpu topology mapping */
+        if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) {
+                /*
+                 * This is a multiprocessor system
+                 * multiprocessor format & multiprocessor mode field are set
+                 */
+
+                if (mpidr & MPIDR_MT_BITMASK) {
+                        /* core performance interdependency */
+                        cpuid_topo->thread_id = (mpidr >> MPIDR_LEVEL0_SHIFT)
+                                & MPIDR_LEVEL0_MASK;
+                        cpuid_topo->core_id = (mpidr >> MPIDR_LEVEL1_SHIFT)
+                                & MPIDR_LEVEL1_MASK;
+                        cpuid_topo->socket_id = (mpidr >> MPIDR_LEVEL2_SHIFT)
+                                & MPIDR_LEVEL2_MASK;
+                } else {
+                        /* largely independent cores */
+                        cpuid_topo->thread_id = -1;
+                        cpuid_topo->core_id = (mpidr >> MPIDR_LEVEL0_SHIFT)
+                                & MPIDR_LEVEL0_MASK;
+                        cpuid_topo->socket_id = (mpidr >> MPIDR_LEVEL1_SHIFT)
+                                & MPIDR_LEVEL1_MASK;
+                }
+        } else {
+                /*
+                 * This is an uniprocessor system
+                 * we are in multiprocessor format but uniprocessor system
+                 * or in the old uniprocessor format
+                 */
+                cpuid_topo->thread_id = -1;
+                cpuid_topo->core_id = 0;
+                cpuid_topo->socket_id = -1;
+        }
+
+        /* update core and thread sibling masks */
+        for_each_possible_cpu(cpu) {
+                struct cputopo_arm *cpu_topo = &cpu_topology[cpu];
+
+                if (cpuid_topo->socket_id == cpu_topo->socket_id) {
+                        cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
+                        if (cpu != cpuid)
+                                cpumask_set_cpu(cpu,
+                                        &cpuid_topo->core_sibling);
+
+                        if (cpuid_topo->core_id == cpu_topo->core_id) {
+                                cpumask_set_cpu(cpuid,
+                                        &cpu_topo->thread_sibling);
+                                if (cpu != cpuid)
+                                        cpumask_set_cpu(cpu,
+                                                &cpuid_topo->thread_sibling);
+                        }
+                }
+        }
+        smp_wmb();
+
+        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,
+                cpu_topology[cpuid].socket_id, mpidr);
+}
+
+/*
+ * init_cpu_topology is called at boot when only one cpu is running
+ * which prevent simultaneous write access to cpu_topology array
+ */
+void init_cpu_topology(void)
+{
+        unsigned int cpu;
+
+        /* init core mask */
+        for_each_possible_cpu(cpu) {
+                struct cputopo_arm *cpu_topo = &(cpu_topology[cpu]);
+
+                cpu_topo->thread_id = -1;
+                cpu_topo->core_id =  -1;
+                cpu_topo->socket_id = -1;
+                cpumask_clear(&cpu_topo->core_sibling);
+                cpumask_clear(&cpu_topo->thread_sibling);
+        }
+        smp_wmb();
+}