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       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/arch_topology.h>
      15                 :            : #include <linux/cpu.h>
      16                 :            : #include <linux/cpufreq.h>
      17                 :            : #include <linux/cpumask.h>
      18                 :            : #include <linux/export.h>
      19                 :            : #include <linux/init.h>
      20                 :            : #include <linux/percpu.h>
      21                 :            : #include <linux/node.h>
      22                 :            : #include <linux/nodemask.h>
      23                 :            : #include <linux/of.h>
      24                 :            : #include <linux/sched.h>
      25                 :            : #include <linux/sched/topology.h>
      26                 :            : #include <linux/slab.h>
      27                 :            : #include <linux/string.h>
      28                 :            : 
      29                 :            : #include <asm/cpu.h>
      30                 :            : #include <asm/cputype.h>
      31                 :            : #include <asm/topology.h>
      32                 :            : 
      33                 :            : /*
      34                 :            :  * cpu capacity scale management
      35                 :            :  */
      36                 :            : 
      37                 :            : /*
      38                 :            :  * cpu capacity table
      39                 :            :  * This per cpu data structure describes the relative capacity of each core.
      40                 :            :  * On a heteregenous system, cores don't have the same computation capacity
      41                 :            :  * and we reflect that difference in the cpu_capacity field so the scheduler
      42                 :            :  * can take this difference into account during load balance. A per cpu
      43                 :            :  * structure is preferred because each CPU updates its own cpu_capacity field
      44                 :            :  * during the load balance except for idle cores. One idle core is selected
      45                 :            :  * to run the rebalance_domains for all idle cores and the cpu_capacity can be
      46                 :            :  * updated during this sequence.
      47                 :            :  */
      48                 :            : 
      49                 :            : #ifdef CONFIG_OF
      50                 :            : struct cpu_efficiency {
      51                 :            :         const char *compatible;
      52                 :            :         unsigned long efficiency;
      53                 :            : };
      54                 :            : 
      55                 :            : /*
      56                 :            :  * Table of relative efficiency of each processors
      57                 :            :  * The efficiency value must fit in 20bit and the final
      58                 :            :  * cpu_scale value must be in the range
      59                 :            :  *   0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2
      60                 :            :  * in order to return at most 1 when DIV_ROUND_CLOSEST
      61                 :            :  * is used to compute the capacity of a CPU.
      62                 :            :  * Processors that are not defined in the table,
      63                 :            :  * use the default SCHED_CAPACITY_SCALE value for cpu_scale.
      64                 :            :  */
      65                 :            : static const struct cpu_efficiency table_efficiency[] = {
      66                 :            :         {"arm,cortex-a15", 3891},
      67                 :            :         {"arm,cortex-a7",  2048},
      68                 :            :         {NULL, },
      69                 :            : };
      70                 :            : 
      71                 :            : static unsigned long *__cpu_capacity;
      72                 :            : #define cpu_capacity(cpu)       __cpu_capacity[cpu]
      73                 :            : 
      74                 :            : static unsigned long middle_capacity = 1;
      75                 :            : static bool cap_from_dt = true;
      76                 :            : 
      77                 :            : /*
      78                 :            :  * Iterate all CPUs' descriptor in DT and compute the efficiency
      79                 :            :  * (as per table_efficiency). Also calculate a middle efficiency
      80                 :            :  * as close as possible to  (max{eff_i} - min{eff_i}) / 2
      81                 :            :  * This is later used to scale the cpu_capacity field such that an
      82                 :            :  * 'average' CPU is of middle capacity. Also see the comments near
      83                 :            :  * table_efficiency[] and update_cpu_capacity().
      84                 :            :  */
      85                 :          3 : static void __init parse_dt_topology(void)
      86                 :            : {
      87                 :            :         const struct cpu_efficiency *cpu_eff;
      88                 :            :         struct device_node *cn = NULL;
      89                 :            :         unsigned long min_capacity = ULONG_MAX;
      90                 :            :         unsigned long max_capacity = 0;
      91                 :            :         unsigned long capacity = 0;
      92                 :            :         int cpu = 0;
      93                 :            : 
      94                 :          3 :         __cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity),
      95                 :            :                                  GFP_NOWAIT);
      96                 :            : 
      97                 :          3 :         for_each_possible_cpu(cpu) {
      98                 :            :                 const u32 *rate;
      99                 :            :                 int len;
     100                 :            : 
     101                 :            :                 /* too early to use cpu->of_node */
     102                 :          3 :                 cn = of_get_cpu_node(cpu, NULL);
     103                 :          3 :                 if (!cn) {
     104                 :          0 :                         pr_err("missing device node for CPU %d\n", cpu);
     105                 :          0 :                         continue;
     106                 :            :                 }
     107                 :            : 
     108                 :          3 :                 if (topology_parse_cpu_capacity(cn, cpu)) {
     109                 :          0 :                         of_node_put(cn);
     110                 :          0 :                         continue;
     111                 :            :                 }
     112                 :            : 
     113                 :          3 :                 cap_from_dt = false;
     114                 :            : 
     115                 :          3 :                 for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)
     116                 :          3 :                         if (of_device_is_compatible(cn, cpu_eff->compatible))
     117                 :            :                                 break;
     118                 :            : 
     119                 :          3 :                 if (cpu_eff->compatible == NULL)
     120                 :          0 :                         continue;
     121                 :            : 
     122                 :          3 :                 rate = of_get_property(cn, "clock-frequency", &len);
     123                 :          3 :                 if (!rate || len != 4) {
     124                 :          0 :                         pr_err("%pOF missing clock-frequency property\n", cn);
     125                 :          0 :                         continue;
     126                 :            :                 }
     127                 :            : 
     128                 :          3 :                 capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
     129                 :            : 
     130                 :            :                 /* Save min capacity of the system */
     131                 :          3 :                 if (capacity < min_capacity)
     132                 :            :                         min_capacity = capacity;
     133                 :            : 
     134                 :            :                 /* Save max capacity of the system */
     135                 :          3 :                 if (capacity > max_capacity)
     136                 :            :                         max_capacity = capacity;
     137                 :            : 
     138                 :          3 :                 cpu_capacity(cpu) = capacity;
     139                 :            :         }
     140                 :            : 
     141                 :            :         /* If min and max capacities are equals, we bypass the update of the
     142                 :            :          * cpu_scale because all CPUs have the same capacity. Otherwise, we
     143                 :            :          * compute a middle_capacity factor that will ensure that the capacity
     144                 :            :          * of an 'average' CPU of the system will be as close as possible to
     145                 :            :          * SCHED_CAPACITY_SCALE, which is the default value, but with the
     146                 :            :          * constraint explained near table_efficiency[].
     147                 :            :          */
     148                 :          3 :         if (4*max_capacity < (3*(max_capacity + min_capacity)))
     149                 :          3 :                 middle_capacity = (min_capacity + max_capacity)
     150                 :          3 :                                 >> (SCHED_CAPACITY_SHIFT+1);
     151                 :            :         else
     152                 :          0 :                 middle_capacity = ((max_capacity / 3)
     153                 :          0 :                                 >> (SCHED_CAPACITY_SHIFT-1)) + 1;
     154                 :            : 
     155                 :          3 :         if (cap_from_dt)
     156                 :          0 :                 topology_normalize_cpu_scale();
     157                 :          3 : }
     158                 :            : 
     159                 :            : /*
     160                 :            :  * Look for a customed capacity of a CPU in the cpu_capacity table during the
     161                 :            :  * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
     162                 :            :  * function returns directly for SMP system.
     163                 :            :  */
     164                 :          3 : static void update_cpu_capacity(unsigned int cpu)
     165                 :            : {
     166                 :          3 :         if (!cpu_capacity(cpu) || cap_from_dt)
     167                 :          3 :                 return;
     168                 :            : 
     169                 :          3 :         topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity);
     170                 :            : 
     171                 :          3 :         pr_info("CPU%u: update cpu_capacity %lu\n",
     172                 :            :                 cpu, topology_get_cpu_scale(cpu));
     173                 :            : }
     174                 :            : 
     175                 :            : #else
     176                 :            : static inline void parse_dt_topology(void) {}
     177                 :            : static inline void update_cpu_capacity(unsigned int cpuid) {}
     178                 :            : #endif
     179                 :            : 
     180                 :            : /*
     181                 :            :  * The current assumption is that we can power gate each core independently.
     182                 :            :  * This will be superseded by DT binding once available.
     183                 :            :  */
     184                 :          0 : const struct cpumask *cpu_corepower_mask(int cpu)
     185                 :            : {
     186                 :          0 :         return &cpu_topology[cpu].thread_sibling;
     187                 :            : }
     188                 :            : 
     189                 :            : /*
     190                 :            :  * store_cpu_topology is called at boot when only one cpu is running
     191                 :            :  * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
     192                 :            :  * which prevents simultaneous write access to cpu_topology array
     193                 :            :  */
     194                 :          3 : void store_cpu_topology(unsigned int cpuid)
     195                 :            : {
     196                 :            :         struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
     197                 :            :         unsigned int mpidr;
     198                 :            : 
     199                 :          3 :         if (cpuid_topo->package_id != -1)
     200                 :            :                 goto topology_populated;
     201                 :            : 
     202                 :            :         mpidr = read_cpuid_mpidr();
     203                 :            : 
     204                 :            :         /* create cpu topology mapping */
     205                 :          3 :         if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) {
     206                 :            :                 /*
     207                 :            :                  * This is a multiprocessor system
     208                 :            :                  * multiprocessor format & multiprocessor mode field are set
     209                 :            :                  */
     210                 :            : 
     211                 :          3 :                 if (mpidr & MPIDR_MT_BITMASK) {
     212                 :            :                         /* core performance interdependency */
     213                 :          0 :                         cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
     214                 :          0 :                         cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
     215                 :          0 :                         cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 2);
     216                 :            :                 } else {
     217                 :            :                         /* largely independent cores */
     218                 :          3 :                         cpuid_topo->thread_id = -1;
     219                 :          3 :                         cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
     220                 :          3 :                         cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
     221                 :            :                 }
     222                 :            :         } else {
     223                 :            :                 /*
     224                 :            :                  * This is an uniprocessor system
     225                 :            :                  * we are in multiprocessor format but uniprocessor system
     226                 :            :                  * or in the old uniprocessor format
     227                 :            :                  */
     228                 :          0 :                 cpuid_topo->thread_id = -1;
     229                 :          0 :                 cpuid_topo->core_id = 0;
     230                 :          0 :                 cpuid_topo->package_id = -1;
     231                 :            :         }
     232                 :            : 
     233                 :          3 :         update_cpu_capacity(cpuid);
     234                 :            : 
     235                 :          3 :         pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
     236                 :            :                 cpuid, cpu_topology[cpuid].thread_id,
     237                 :            :                 cpu_topology[cpuid].core_id,
     238                 :            :                 cpu_topology[cpuid].package_id, mpidr);
     239                 :            : 
     240                 :            : topology_populated:
     241                 :          3 :         update_siblings_masks(cpuid);
     242                 :          3 : }
     243                 :            : 
     244                 :            : static inline int cpu_corepower_flags(void)
     245                 :            : {
     246                 :            :         return SD_SHARE_PKG_RESOURCES  | SD_SHARE_POWERDOMAIN;
     247                 :            : }
     248                 :            : 
     249                 :            : static struct sched_domain_topology_level arm_topology[] = {
     250                 :            : #ifdef CONFIG_SCHED_MC
     251                 :            :         { cpu_corepower_mask, cpu_corepower_flags, SD_INIT_NAME(GMC) },
     252                 :            :         { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
     253                 :            : #endif
     254                 :            :         { cpu_cpu_mask, SD_INIT_NAME(DIE) },
     255                 :            :         { NULL, },
     256                 :            : };
     257                 :            : 
     258                 :            : /*
     259                 :            :  * init_cpu_topology is called at boot when only one cpu is running
     260                 :            :  * which prevent simultaneous write access to cpu_topology array
     261                 :            :  */
     262                 :          3 : void __init init_cpu_topology(void)
     263                 :            : {
     264                 :          3 :         reset_cpu_topology();
     265                 :          3 :         smp_wmb();
     266                 :            : 
     267                 :          3 :         parse_dt_topology();
     268                 :            : 
     269                 :            :         /* Set scheduler topology descriptor */
     270                 :          3 :         set_sched_topology(arm_topology);
     271                 :          3 : }