linux/drivers/cpuidle/cpuidle-big_little.c
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   1/*
   2 * Copyright (c) 2013 ARM/Linaro
   3 *
   4 * Authors: Daniel Lezcano <daniel.lezcano@linaro.org>
   5 *          Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
   6 *          Nicolas Pitre <nicolas.pitre@linaro.org>
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License version 2 as
  10 * published by the Free Software Foundation.
  11 *
  12 * Maintainer: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
  13 * Maintainer: Daniel Lezcano <daniel.lezcano@linaro.org>
  14 */
  15#include <linux/cpuidle.h>
  16#include <linux/cpu_pm.h>
  17#include <linux/slab.h>
  18#include <linux/of.h>
  19
  20#include <asm/cpu.h>
  21#include <asm/cputype.h>
  22#include <asm/cpuidle.h>
  23#include <asm/mcpm.h>
  24#include <asm/smp_plat.h>
  25#include <asm/suspend.h>
  26
  27static int bl_enter_powerdown(struct cpuidle_device *dev,
  28                              struct cpuidle_driver *drv, int idx);
  29
  30/*
  31 * NB: Owing to current menu governor behaviour big and LITTLE
  32 * index 1 states have to define exit_latency and target_residency for
  33 * cluster state since, when all CPUs in a cluster hit it, the cluster
  34 * can be shutdown. This means that when a single CPU enters this state
  35 * the exit_latency and target_residency values are somewhat overkill.
  36 * There is no notion of cluster states in the menu governor, so CPUs
  37 * have to define CPU states where possibly the cluster will be shutdown
  38 * depending on the state of other CPUs. idle states entry and exit happen
  39 * at random times; however the cluster state provides target_residency
  40 * values as if all CPUs in a cluster enter the state at once; this is
  41 * somewhat optimistic and behaviour should be fixed either in the governor
  42 * or in the MCPM back-ends.
  43 * To make this driver 100% generic the number of states and the exit_latency
  44 * target_residency values must be obtained from device tree bindings.
  45 *
  46 * exit_latency: refers to the TC2 vexpress test chip and depends on the
  47 * current cluster operating point. It is the time it takes to get the CPU
  48 * up and running when the CPU is powered up on cluster wake-up from shutdown.
  49 * Current values for big and LITTLE clusters are provided for clusters
  50 * running at default operating points.
  51 *
  52 * target_residency: it is the minimum amount of time the cluster has
  53 * to be down to break even in terms of power consumption. cluster
  54 * shutdown has inherent dynamic power costs (L2 writebacks to DRAM
  55 * being the main factor) that depend on the current operating points.
  56 * The current values for both clusters are provided for a CPU whose half
  57 * of L2 lines are dirty and require cleaning to DRAM, and takes into
  58 * account leakage static power values related to the vexpress TC2 testchip.
  59 */
  60static struct cpuidle_driver bl_idle_little_driver = {
  61        .name = "little_idle",
  62        .owner = THIS_MODULE,
  63        .states[0] = ARM_CPUIDLE_WFI_STATE,
  64        .states[1] = {
  65                .enter                  = bl_enter_powerdown,
  66                .exit_latency           = 700,
  67                .target_residency       = 2500,
  68                .flags                  = CPUIDLE_FLAG_TIME_VALID |
  69                                          CPUIDLE_FLAG_TIMER_STOP,
  70                .name                   = "C1",
  71                .desc                   = "ARM little-cluster power down",
  72        },
  73        .state_count = 2,
  74};
  75
  76static struct cpuidle_driver bl_idle_big_driver = {
  77        .name = "big_idle",
  78        .owner = THIS_MODULE,
  79        .states[0] = ARM_CPUIDLE_WFI_STATE,
  80        .states[1] = {
  81                .enter                  = bl_enter_powerdown,
  82                .exit_latency           = 500,
  83                .target_residency       = 2000,
  84                .flags                  = CPUIDLE_FLAG_TIME_VALID |
  85                                          CPUIDLE_FLAG_TIMER_STOP,
  86                .name                   = "C1",
  87                .desc                   = "ARM big-cluster power down",
  88        },
  89        .state_count = 2,
  90};
  91
  92/*
  93 * notrace prevents trace shims from getting inserted where they
  94 * should not. Global jumps and ldrex/strex must not be inserted
  95 * in power down sequences where caches and MMU may be turned off.
  96 */
  97static int notrace bl_powerdown_finisher(unsigned long arg)
  98{
  99        /* MCPM works with HW CPU identifiers */
 100        unsigned int mpidr = read_cpuid_mpidr();
 101        unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
 102        unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
 103
 104        mcpm_set_entry_vector(cpu, cluster, cpu_resume);
 105
 106        /*
 107         * Residency value passed to mcpm_cpu_suspend back-end
 108         * has to be given clear semantics. Set to 0 as a
 109         * temporary value.
 110         */
 111        mcpm_cpu_suspend(0);
 112
 113        /* return value != 0 means failure */
 114        return 1;
 115}
 116
 117/**
 118 * bl_enter_powerdown - Programs CPU to enter the specified state
 119 * @dev: cpuidle device
 120 * @drv: The target state to be programmed
 121 * @idx: state index
 122 *
 123 * Called from the CPUidle framework to program the device to the
 124 * specified target state selected by the governor.
 125 */
 126static int bl_enter_powerdown(struct cpuidle_device *dev,
 127                                struct cpuidle_driver *drv, int idx)
 128{
 129        cpu_pm_enter();
 130
 131        cpu_suspend(0, bl_powerdown_finisher);
 132
 133        /* signals the MCPM core that CPU is out of low power state */
 134        mcpm_cpu_powered_up();
 135
 136        cpu_pm_exit();
 137
 138        return idx;
 139}
 140
 141static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int cpu_id)
 142{
 143        struct cpuinfo_arm *cpu_info;
 144        struct cpumask *cpumask;
 145        unsigned long cpuid;
 146        int cpu;
 147
 148        cpumask = kzalloc(cpumask_size(), GFP_KERNEL);
 149        if (!cpumask)
 150                return -ENOMEM;
 151
 152        for_each_possible_cpu(cpu) {
 153                cpu_info = &per_cpu(cpu_data, cpu);
 154                cpuid = is_smp() ? cpu_info->cpuid : read_cpuid_id();
 155
 156                /* read cpu id part number */
 157                if ((cpuid & 0xFFF0) == cpu_id)
 158                        cpumask_set_cpu(cpu, cpumask);
 159        }
 160
 161        drv->cpumask = cpumask;
 162
 163        return 0;
 164}
 165
 166static int __init bl_idle_init(void)
 167{
 168        int ret;
 169
 170        /*
 171         * Initialize the driver just for a compliant set of machines
 172         */
 173        if (!of_machine_is_compatible("arm,vexpress,v2p-ca15_a7"))
 174                return -ENODEV;
 175        /*
 176         * For now the differentiation between little and big cores
 177         * is based on the part number. A7 cores are considered little
 178         * cores, A15 are considered big cores. This distinction may
 179         * evolve in the future with a more generic matching approach.
 180         */
 181        ret = bl_idle_driver_init(&bl_idle_little_driver,
 182                                  ARM_CPU_PART_CORTEX_A7);
 183        if (ret)
 184                return ret;
 185
 186        ret = bl_idle_driver_init(&bl_idle_big_driver, ARM_CPU_PART_CORTEX_A15);
 187        if (ret)
 188                goto out_uninit_little;
 189
 190        ret = cpuidle_register(&bl_idle_little_driver, NULL);
 191        if (ret)
 192                goto out_uninit_big;
 193
 194        ret = cpuidle_register(&bl_idle_big_driver, NULL);
 195        if (ret)
 196                goto out_unregister_little;
 197
 198        return 0;
 199
 200out_unregister_little:
 201        cpuidle_unregister(&bl_idle_little_driver);
 202out_uninit_big:
 203        kfree(bl_idle_big_driver.cpumask);
 204out_uninit_little:
 205        kfree(bl_idle_little_driver.cpumask);
 206
 207        return ret;
 208}
 209device_initcall(bl_idle_init);
 210
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