arch/arm/kernel/topology.c

   1 /*
   2  * arch/arm/kernel/topology.c
   3  *
   4  * Copyright (C) 2011 Linaro Limited.
   5  * Written by: Vincent Guittot
   6  *
   7  * based on arch/sh/kernel/topology.c
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file "COPYING" in the main directory of this archive
  11  * for more details.
  12  */
  13
  14 #include <linux/cpu.h>
  15 #include <linux/cpumask.h>
  16 #include <linux/init.h>
  17 #include <linux/percpu.h>
  18 #include <linux/node.h>
  19 #include <linux/nodemask.h>
  20 #include <linux/sched.h>
  21
  22 #include <asm/cputype.h>
  23 #include <asm/topology.h>
  24
  25 #define MPIDR_SMP_BITMASK (0x3 << 30)
  26 #define MPIDR_SMP_VALUE (0x2 << 30)
  27
  28 #define MPIDR_MT_BITMASK (0x1 << 24)
  29
  30 /*
  31  * These masks reflect the current use of the affinity levels.
  32  * The affinity level can be up to 16 bits according to ARM ARM
  33  */
  34
  35 #define MPIDR_LEVEL0_MASK 0x3
  36 #define MPIDR_LEVEL0_SHIFT 0
  37
  38 #define MPIDR_LEVEL1_MASK 0xF
  39 #define MPIDR_LEVEL1_SHIFT 8
  40
  41 #define MPIDR_LEVEL2_MASK 0xFF
  42 #define MPIDR_LEVEL2_SHIFT 16
  43
  44 struct cputopo_arm cpu_topology[NR_CPUS];
  45
  46 const struct cpumask *cpu_coregroup_mask(int cpu)
  47 {
  48         return &cpu_topology[cpu].core_sibling;
  49 }
  50
  51 /*
  52  * store_cpu_topology is called at boot when only one cpu is running
  53  * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
  54  * which prevents simultaneous write access to cpu_topology array
  55  */
  56 void store_cpu_topology(unsigned int cpuid)
  57 {
  58         struct cputopo_arm *cpuid_topo = &cpu_topology[cpuid];
  59         unsigned int mpidr;
  60         unsigned int cpu;
  61
  62         /* If the cpu topology has been already set, just return */
  63         if (cpuid_topo->core_id != -1)
  64                 return;
  65
  66         mpidr = read_cpuid_mpidr();
  67
  68         /* create cpu topology mapping */
  69         if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) {
  70                 /*
  71                  * This is a multiprocessor system
  72                  * multiprocessor format & multiprocessor mode field are set
  73                  */
  74
  75                 if (mpidr & MPIDR_MT_BITMASK) {
  76                         /* core performance interdependency */
  77                         cpuid_topo->thread_id = (mpidr >> MPIDR_LEVEL0_SHIFT)
  78                                 & MPIDR_LEVEL0_MASK;
  79                         cpuid_topo->core_id = (mpidr >> MPIDR_LEVEL1_SHIFT)
  80                                 & MPIDR_LEVEL1_MASK;
  81                         cpuid_topo->socket_id = (mpidr >> MPIDR_LEVEL2_SHIFT)
  82                                 & MPIDR_LEVEL2_MASK;
  83                 } else {
  84                         /* largely independent cores */
  85                         cpuid_topo->thread_id = -1;
  86                         cpuid_topo->core_id = (mpidr >> MPIDR_LEVEL0_SHIFT)
  87                                 & MPIDR_LEVEL0_MASK;
  88                         cpuid_topo->socket_id = (mpidr >> MPIDR_LEVEL1_SHIFT)
  89                                 & MPIDR_LEVEL1_MASK;
  90                 }
  91         } else {
  92                 /*
  93                  * This is an uniprocessor system
  94                  * we are in multiprocessor format but uniprocessor system
  95                  * or in the old uniprocessor format
  96                  */
  97                 cpuid_topo->thread_id = -1;
  98                 cpuid_topo->core_id = 0;
  99                 cpuid_topo->socket_id = -1;
 100         }
 101
 102         /* update core and thread sibling masks */
 103         for_each_possible_cpu(cpu) {
 104                 struct cputopo_arm *cpu_topo = &cpu_topology[cpu];
 105
 106                 if (cpuid_topo->socket_id == cpu_topo->socket_id) {
 107                         cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
 108                         if (cpu != cpuid)
 109                                 cpumask_set_cpu(cpu,
 110                                         &cpuid_topo->core_sibling);
 111
 112                         if (cpuid_topo->core_id == cpu_topo->core_id) {
 113                                 cpumask_set_cpu(cpuid,
 114                                         &cpu_topo->thread_sibling);
 115                                 if (cpu != cpuid)
 116                                         cpumask_set_cpu(cpu,
 117                                                 &cpuid_topo->thread_sibling);
 118                         }
 119                 }
 120         }
 121         smp_wmb();
 122
 123         printk(KERN_INFO "CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
 124                 cpuid, cpu_topology[cpuid].thread_id,
 125                 cpu_topology[cpuid].core_id,
 126                 cpu_topology[cpuid].socket_id, mpidr);
 127 }
 128
 129 /*
 130  * init_cpu_topology is called at boot when only one cpu is running
 131  * which prevent simultaneous write access to cpu_topology array
 132  */
 133 void init_cpu_topology(void)
 134 {
 135         unsigned int cpu;
 136
 137         /* init core mask */
 138         for_each_possible_cpu(cpu) {
 139                 struct cputopo_arm *cpu_topo = &(cpu_topology[cpu]);
 140
 141                 cpu_topo->thread_id = -1;
 142                 cpu_topo->core_id =  -1;
 143                 cpu_topo->socket_id = -1;
 144                 cpumask_clear(&cpu_topo->core_sibling);
 145                 cpumask_clear(&cpu_topo->thread_sibling);
 146         }
 147         smp_wmb();
 148 }