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245 lines
6.8 KiB
245 lines
6.8 KiB
/* |
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* arch/arm/kernel/topology.c |
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* |
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* Copyright (C) 2011 Linaro Limited. |
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* Written by: Vincent Guittot |
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* |
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* based on arch/sh/kernel/topology.c |
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* |
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* This file is subject to the terms and conditions of the GNU General Public |
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* License. See the file "COPYING" in the main directory of this archive |
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* for more details. |
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*/ |
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#include <linux/arch_topology.h> |
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#include <linux/cpu.h> |
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#include <linux/cpufreq.h> |
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#include <linux/cpumask.h> |
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#include <linux/export.h> |
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#include <linux/init.h> |
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#include <linux/percpu.h> |
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#include <linux/node.h> |
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#include <linux/nodemask.h> |
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#include <linux/of.h> |
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#include <linux/sched.h> |
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#include <linux/sched/topology.h> |
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#include <linux/slab.h> |
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#include <linux/string.h> |
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#include <asm/cpu.h> |
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#include <asm/cputype.h> |
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#include <asm/topology.h> |
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/* |
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* cpu capacity scale management |
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*/ |
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/* |
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* cpu capacity table |
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* This per cpu data structure describes the relative capacity of each core. |
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* On a heteregenous system, cores don't have the same computation capacity |
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* and we reflect that difference in the cpu_capacity field so the scheduler |
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* can take this difference into account during load balance. A per cpu |
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* structure is preferred because each CPU updates its own cpu_capacity field |
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* during the load balance except for idle cores. One idle core is selected |
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* to run the rebalance_domains for all idle cores and the cpu_capacity can be |
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* updated during this sequence. |
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*/ |
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#ifdef CONFIG_OF |
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struct cpu_efficiency { |
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const char *compatible; |
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unsigned long efficiency; |
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}; |
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/* |
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* Table of relative efficiency of each processors |
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* The efficiency value must fit in 20bit and the final |
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* cpu_scale value must be in the range |
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* 0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2 |
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* in order to return at most 1 when DIV_ROUND_CLOSEST |
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* is used to compute the capacity of a CPU. |
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* Processors that are not defined in the table, |
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* use the default SCHED_CAPACITY_SCALE value for cpu_scale. |
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*/ |
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static const struct cpu_efficiency table_efficiency[] = { |
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{"arm,cortex-a15", 3891}, |
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{"arm,cortex-a7", 2048}, |
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{NULL, }, |
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}; |
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static unsigned long *__cpu_capacity; |
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#define cpu_capacity(cpu) __cpu_capacity[cpu] |
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static unsigned long middle_capacity = 1; |
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static bool cap_from_dt = true; |
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/* |
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* Iterate all CPUs' descriptor in DT and compute the efficiency |
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* (as per table_efficiency). Also calculate a middle efficiency |
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* as close as possible to (max{eff_i} - min{eff_i}) / 2 |
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* This is later used to scale the cpu_capacity field such that an |
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* 'average' CPU is of middle capacity. Also see the comments near |
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* table_efficiency[] and update_cpu_capacity(). |
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*/ |
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static void __init parse_dt_topology(void) |
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{ |
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const struct cpu_efficiency *cpu_eff; |
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struct device_node *cn = NULL; |
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unsigned long min_capacity = ULONG_MAX; |
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unsigned long max_capacity = 0; |
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unsigned long capacity = 0; |
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int cpu = 0; |
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__cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity), |
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GFP_NOWAIT); |
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for_each_possible_cpu(cpu) { |
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const __be32 *rate; |
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int len; |
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/* too early to use cpu->of_node */ |
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cn = of_get_cpu_node(cpu, NULL); |
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if (!cn) { |
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pr_err("missing device node for CPU %d\n", cpu); |
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continue; |
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} |
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if (topology_parse_cpu_capacity(cn, cpu)) { |
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of_node_put(cn); |
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continue; |
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} |
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cap_from_dt = false; |
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for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++) |
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if (of_device_is_compatible(cn, cpu_eff->compatible)) |
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break; |
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if (cpu_eff->compatible == NULL) |
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continue; |
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rate = of_get_property(cn, "clock-frequency", &len); |
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if (!rate || len != 4) { |
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pr_err("%pOF missing clock-frequency property\n", cn); |
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continue; |
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} |
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capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency; |
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/* Save min capacity of the system */ |
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if (capacity < min_capacity) |
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min_capacity = capacity; |
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/* Save max capacity of the system */ |
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if (capacity > max_capacity) |
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max_capacity = capacity; |
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cpu_capacity(cpu) = capacity; |
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} |
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/* If min and max capacities are equals, we bypass the update of the |
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* cpu_scale because all CPUs have the same capacity. Otherwise, we |
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* compute a middle_capacity factor that will ensure that the capacity |
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* of an 'average' CPU of the system will be as close as possible to |
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* SCHED_CAPACITY_SCALE, which is the default value, but with the |
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* constraint explained near table_efficiency[]. |
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*/ |
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if (4*max_capacity < (3*(max_capacity + min_capacity))) |
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middle_capacity = (min_capacity + max_capacity) |
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>> (SCHED_CAPACITY_SHIFT+1); |
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else |
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middle_capacity = ((max_capacity / 3) |
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>> (SCHED_CAPACITY_SHIFT-1)) + 1; |
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if (cap_from_dt) |
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topology_normalize_cpu_scale(); |
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} |
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/* |
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* Look for a customed capacity of a CPU in the cpu_capacity table during the |
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* boot. The update of all CPUs is in O(n^2) for heteregeneous system but the |
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* function returns directly for SMP system. |
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*/ |
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static void update_cpu_capacity(unsigned int cpu) |
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{ |
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if (!cpu_capacity(cpu) || cap_from_dt) |
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return; |
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topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity); |
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pr_info("CPU%u: update cpu_capacity %lu\n", |
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cpu, topology_get_cpu_scale(cpu)); |
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} |
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#else |
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static inline void parse_dt_topology(void) {} |
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static inline void update_cpu_capacity(unsigned int cpuid) {} |
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#endif |
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/* |
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* store_cpu_topology is called at boot when only one cpu is running |
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* and with the mutex cpu_hotplug.lock locked, when several cpus have booted, |
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* which prevents simultaneous write access to cpu_topology array |
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*/ |
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void store_cpu_topology(unsigned int cpuid) |
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{ |
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struct cpu_topology *cpuid_topo = &cpu_topology[cpuid]; |
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unsigned int mpidr; |
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if (cpuid_topo->package_id != -1) |
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goto topology_populated; |
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mpidr = read_cpuid_mpidr(); |
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/* create cpu topology mapping */ |
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if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) { |
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/* |
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* This is a multiprocessor system |
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* multiprocessor format & multiprocessor mode field are set |
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*/ |
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if (mpidr & MPIDR_MT_BITMASK) { |
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/* core performance interdependency */ |
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cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL(mpidr, 0); |
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cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 1); |
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cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 2); |
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} else { |
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/* largely independent cores */ |
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cpuid_topo->thread_id = -1; |
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cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0); |
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cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 1); |
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} |
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} else { |
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/* |
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* This is an uniprocessor system |
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* we are in multiprocessor format but uniprocessor system |
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* or in the old uniprocessor format |
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*/ |
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cpuid_topo->thread_id = -1; |
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cpuid_topo->core_id = 0; |
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cpuid_topo->package_id = -1; |
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} |
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update_cpu_capacity(cpuid); |
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pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n", |
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cpuid, cpu_topology[cpuid].thread_id, |
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cpu_topology[cpuid].core_id, |
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cpu_topology[cpuid].package_id, mpidr); |
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topology_populated: |
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update_siblings_masks(cpuid); |
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} |
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/* |
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* init_cpu_topology is called at boot when only one cpu is running |
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* which prevent simultaneous write access to cpu_topology array |
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*/ |
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void __init init_cpu_topology(void) |
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{ |
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reset_cpu_topology(); |
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smp_wmb(); |
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parse_dt_topology(); |
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}
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