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/of.h>
  21 #include <linux/sched.h>
  22 #include <linux/slab.h>
  23
  24 #include <asm/cputype.h>
  25 #include <asm/topology.h>
  26
  27 /*
  28  * cpu power scale management
  29  */
  30
  31 /*
  32  * cpu power table
  33  * This per cpu data structure describes the relative capacity of each core.
  34  * On a heteregenous system, cores don't have the same computation capacity
  35  * and we reflect that difference in the cpu_power field so the scheduler can
  36  * take this difference into account during load balance. A per cpu structure
  37  * is preferred because each CPU updates its own cpu_power field during the
  38  * load balance except for idle cores. One idle core is selected to run the
  39  * rebalance_domains for all idle cores and the cpu_power can be updated
  40  * during this sequence.
  41  */
  42 static DEFINE_PER_CPU(unsigned long, cpu_scale);
  43
  44 unsigned long arch_scale_freq_power(struct sched_domain *sd, int cpu)
  45 {
  46         return per_cpu(cpu_scale, cpu);
  47 }
  48
  49 static void set_power_scale(unsigned int cpu, unsigned long power)
  50 {
  51         per_cpu(cpu_scale, cpu) = power;
  52 }
  53
  54 #ifdef CONFIG_OF
  55 struct cpu_efficiency {
  56         const char *compatible;
  57         unsigned long efficiency;
  58 };
  59
  60 /*
  61  * Table of relative efficiency of each processors
  62  * The efficiency value must fit in 20bit and the final
  63  * cpu_scale value must be in the range
  64  *   0 < cpu_scale < 3*SCHED_POWER_SCALE/2
  65  * in order to return at most 1 when DIV_ROUND_CLOSEST
  66  * is used to compute the capacity of a CPU.
  67  * Processors that are not defined in the table,
  68  * use the default SCHED_POWER_SCALE value for cpu_scale.
  69  */
  70 struct cpu_efficiency table_efficiency[] = {
  71         {"arm,cortex-a15", 3891},
  72         {"arm,cortex-a7",  2048},
  73         {NULL, },
  74 };
  75
  76 struct cpu_capacity {
  77         unsigned long hwid;
  78         unsigned long capacity;
  79 };
  80
  81 struct cpu_capacity *cpu_capacity;
  82
  83 unsigned long middle_capacity = 1;
  84
  85 /*
  86  * Iterate all CPUs' descriptor in DT and compute the efficiency
  87  * (as per table_efficiency). Also calculate a middle efficiency
  88  * as close as possible to  (max{eff_i} - min{eff_i}) / 2
  89  * This is later used to scale the cpu_power field such that an
  90  * 'average' CPU is of middle power. Also see the comments near
  91  * table_efficiency[] and update_cpu_power().
  92  */
  93 static void __init parse_dt_topology(void)
  94 {
  95         struct cpu_efficiency *cpu_eff;
  96         struct device_node *cn = NULL;
  97         unsigned long min_capacity = (unsigned long)(-1);
  98         unsigned long max_capacity = 0;
  99         unsigned long capacity = 0;
 100         int alloc_size, cpu = 0;
 101
 102         alloc_size = nr_cpu_ids * sizeof(struct cpu_capacity);
 103         cpu_capacity = kzalloc(alloc_size, GFP_NOWAIT);
 104
 105         while ((cn = of_find_node_by_type(cn, "cpu"))) {
 106                 const u32 *rate, *reg;
 107                 int len;
 108
 109                 if (cpu >= num_possible_cpus())
 110                         break;
 111
 112                 for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)
 113                         if (of_device_is_compatible(cn, cpu_eff->compatible))
 114                                 break;
 115
 116                 if (cpu_eff->compatible == NULL)
 117                         continue;
 118
 119                 rate = of_get_property(cn, "clock-frequency", &len);
 120                 if (!rate || len != 4) {
 121                         pr_err("%s missing clock-frequency property\n",
 122                                 cn->full_name);
 123                         continue;
 124                 }
 125
 126                 reg = of_get_property(cn, "reg", &len);
 127                 if (!reg || len != 4) {
 128                         pr_err("%s missing reg property\n", cn->full_name);
 129                         continue;
 130                 }
 131
 132                 capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
 133
 134                 /* Save min capacity of the system */
 135                 if (capacity < min_capacity)
 136                         min_capacity = capacity;
 137
 138                 /* Save max capacity of the system */
 139                 if (capacity > max_capacity)
 140                         max_capacity = capacity;
 141
 142                 cpu_capacity[cpu].capacity = capacity;
 143                 cpu_capacity[cpu++].hwid = be32_to_cpup(reg);
 144         }
 145
 146         if (cpu < num_possible_cpus())
 147                 cpu_capacity[cpu].hwid = (unsigned long)(-1);
 148
 149         /* If min and max capacities are equals, we bypass the update of the
 150          * cpu_scale because all CPUs have the same capacity. Otherwise, we
 151          * compute a middle_capacity factor that will ensure that the capacity
 152          * of an 'average' CPU of the system will be as close as possible to
 153          * SCHED_POWER_SCALE, which is the default value, but with the
 154          * constraint explained near table_efficiency[].
 155          */
 156         if (min_capacity == max_capacity)
 157                 cpu_capacity[0].hwid = (unsigned long)(-1);
 158         else if (4*max_capacity < (3*(max_capacity + min_capacity)))
 159                 middle_capacity = (min_capacity + max_capacity)
 160                                 >> (SCHED_POWER_SHIFT+1);
 161         else
 162                 middle_capacity = ((max_capacity / 3)
 163                                 >> (SCHED_POWER_SHIFT-1)) + 1;
 164
 165 }
 166
 167 /*
 168  * Look for a customed capacity of a CPU in the cpu_capacity table during the
 169  * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
 170  * function returns directly for SMP system.
 171  */
 172 void update_cpu_power(unsigned int cpu, unsigned long hwid)
 173 {
 174         unsigned int idx = 0;
 175
 176         /* look for the cpu's hwid in the cpu capacity table */
 177         for (idx = 0; idx < num_possible_cpus(); idx++) {
 178                 if (cpu_capacity[idx].hwid == hwid)
 179                         break;
 180
 181                 if (cpu_capacity[idx].hwid == -1)
 182                         return;
 183         }
 184
 185         if (idx == num_possible_cpus())
 186                 return;
 187
 188         set_power_scale(cpu, cpu_capacity[idx].capacity / middle_capacity);
 189
 190         printk(KERN_INFO "CPU%u: update cpu_power %lu\n",
 191                 cpu, arch_scale_freq_power(NULL, cpu));
 192 }
 193
 194 #else
 195 static inline void parse_dt_topology(void) {}
 196 static inline void update_cpu_power(unsigned int cpuid, unsigned int mpidr) {}
 197 #endif
 198
 199  /*
 200  * cpu topology table
 201  */
 202 struct cputopo_arm cpu_topology[NR_CPUS];
 203
 204 const struct cpumask *cpu_coregroup_mask(int cpu)
 205 {
 206         return &cpu_topology[cpu].core_sibling;
 207 }
 208
 209 void update_siblings_masks(unsigned int cpuid)
 210 {
 211         struct cputopo_arm *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
 212         int cpu;
 213
 214         /* update core and thread sibling masks */
 215         for_each_possible_cpu(cpu) {
 216                 cpu_topo = &cpu_topology[cpu];
 217
 218                 if (cpuid_topo->socket_id != cpu_topo->socket_id)
 219                         continue;
 220
 221                 cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
 222                 if (cpu != cpuid)
 223                         cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
 224
 225                 if (cpuid_topo->core_id != cpu_topo->core_id)
 226                         continue;
 227
 228                 cpumask_set_cpu(cpuid, &cpu_topo->thread_sibling);
 229                 if (cpu != cpuid)
 230                         cpumask_set_cpu(cpu, &cpuid_topo->thread_sibling);
 231         }
 232         smp_wmb();
 233 }
 234
 235 /*
 236  * store_cpu_topology is called at boot when only one cpu is running
 237  * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
 238  * which prevents simultaneous write access to cpu_topology array
 239  */
 240 void store_cpu_topology(unsigned int cpuid)
 241 {
 242         struct cputopo_arm *cpuid_topo = &cpu_topology[cpuid];
 243         unsigned int mpidr;
 244
 245         /* If the cpu topology has been already set, just return */
 246         if (cpuid_topo->core_id != -1)
 247                 return;
 248
 249         mpidr = read_cpuid_mpidr();
 250
 251         /* create cpu topology mapping */
 252         if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) {
 253                 /*
 254                  * This is a multiprocessor system
 255                  * multiprocessor format & multiprocessor mode field are set
 256                  */
 257
 258                 if (mpidr & MPIDR_MT_BITMASK) {
 259                         /* core performance interdependency */
 260                         cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
 261                         cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
 262                         cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL(mpidr, 2);
 263                 } else {
 264                         /* largely independent cores */
 265                         cpuid_topo->thread_id = -1;
 266                         cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
 267                         cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
 268                 }
 269         } else {
 270                 /*
 271                  * This is an uniprocessor system
 272                  * we are in multiprocessor format but uniprocessor system
 273                  * or in the old uniprocessor format
 274                  */
 275                 cpuid_topo->thread_id = -1;
 276                 cpuid_topo->core_id = 0;
 277                 cpuid_topo->socket_id = -1;
 278         }
 279
 280         update_siblings_masks(cpuid);
 281
 282         update_cpu_power(cpuid, mpidr & MPIDR_HWID_BITMASK);
 283
 284         printk(KERN_INFO "CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
 285                 cpuid, cpu_topology[cpuid].thread_id,
 286                 cpu_topology[cpuid].core_id,
 287                 cpu_topology[cpuid].socket_id, mpidr);
 288 }
 289
 290 /*
 291  * init_cpu_topology is called at boot when only one cpu is running
 292  * which prevent simultaneous write access to cpu_topology array
 293  */
 294 void __init init_cpu_topology(void)
 295 {
 296         unsigned int cpu;
 297
 298         /* init core mask and power*/
 299         for_each_possible_cpu(cpu) {
 300                 struct cputopo_arm *cpu_topo = &(cpu_topology[cpu]);
 301
 302                 cpu_topo->thread_id = -1;
 303                 cpu_topo->core_id =  -1;
 304                 cpu_topo->socket_id = -1;
 305                 cpumask_clear(&cpu_topo->core_sibling);
 306                 cpumask_clear(&cpu_topo->thread_sibling);
 307
 308                 set_power_scale(cpu, SCHED_POWER_SCALE);
 309         }
 310         smp_wmb();
 311
 312         parse_dt_topology();
 313 }