drivers/cpuidle/cpuidle-big_little.c

   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
  27 #include "dt_idle_states.h"
  28
  29 static int bl_enter_powerdown(struct cpuidle_device *dev,
  30                               struct cpuidle_driver *drv, int idx);
  31
  32 /*
  33  * NB: Owing to current menu governor behaviour big and LITTLE
  34  * index 1 states have to define exit_latency and target_residency for
  35  * cluster state since, when all CPUs in a cluster hit it, the cluster
  36  * can be shutdown. This means that when a single CPU enters this state
  37  * the exit_latency and target_residency values are somewhat overkill.
  38  * There is no notion of cluster states in the menu governor, so CPUs
  39  * have to define CPU states where possibly the cluster will be shutdown
  40  * depending on the state of other CPUs. idle states entry and exit happen
  41  * at random times; however the cluster state provides target_residency
  42  * values as if all CPUs in a cluster enter the state at once; this is
  43  * somewhat optimistic and behaviour should be fixed either in the governor
  44  * or in the MCPM back-ends.
  45  * To make this driver 100% generic the number of states and the exit_latency
  46  * target_residency values must be obtained from device tree bindings.
  47  *
  48  * exit_latency: refers to the TC2 vexpress test chip and depends on the
  49  * current cluster operating point. It is the time it takes to get the CPU
  50  * up and running when the CPU is powered up on cluster wake-up from shutdown.
  51  * Current values for big and LITTLE clusters are provided for clusters
  52  * running at default operating points.
  53  *
  54  * target_residency: it is the minimum amount of time the cluster has
  55  * to be down to break even in terms of power consumption. cluster
  56  * shutdown has inherent dynamic power costs (L2 writebacks to DRAM
  57  * being the main factor) that depend on the current operating points.
  58  * The current values for both clusters are provided for a CPU whose half
  59  * of L2 lines are dirty and require cleaning to DRAM, and takes into
  60  * account leakage static power values related to the vexpress TC2 testchip.
  61  */
  62 static struct cpuidle_driver bl_idle_little_driver = {
  63         .name = "little_idle",
  64         .owner = THIS_MODULE,
  65         .states[0] = ARM_CPUIDLE_WFI_STATE,
  66         .states[1] = {
  67                 .enter                  = bl_enter_powerdown,
  68                 .exit_latency           = 700,
  69                 .target_residency       = 2500,
  70                 .flags                  = CPUIDLE_FLAG_TIMER_STOP,
  71                 .name                   = "C1",
  72                 .desc                   = "ARM little-cluster power down",
  73         },
  74         .state_count = 2,
  75 };
  76
  77 static const struct of_device_id bl_idle_state_match[] __initconst = {
  78         { .compatible = "arm,idle-state",
  79           .data = bl_enter_powerdown },
  80         { },
  81 };
  82
  83 static struct cpuidle_driver bl_idle_big_driver = {
  84         .name = "big_idle",
  85         .owner = THIS_MODULE,
  86         .states[0] = ARM_CPUIDLE_WFI_STATE,
  87         .states[1] = {
  88                 .enter                  = bl_enter_powerdown,
  89                 .exit_latency           = 500,
  90                 .target_residency       = 2000,
  91                 .flags                  = CPUIDLE_FLAG_TIMER_STOP,
  92                 .name                   = "C1",
  93                 .desc                   = "ARM big-cluster power down",
  94         },
  95         .state_count = 2,
  96 };
  97
  98 /*
  99  * notrace prevents trace shims from getting inserted where they
 100  * should not. Global jumps and ldrex/strex must not be inserted
 101  * in power down sequences where caches and MMU may be turned off.
 102  */
 103 static int notrace bl_powerdown_finisher(unsigned long arg)
 104 {
 105         /* MCPM works with HW CPU identifiers */
 106         unsigned int mpidr = read_cpuid_mpidr();
 107         unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
 108         unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
 109
 110         mcpm_set_entry_vector(cpu, cluster, cpu_resume);
 111
 112         /*
 113          * Residency value passed to mcpm_cpu_suspend back-end
 114          * has to be given clear semantics. Set to 0 as a
 115          * temporary value.
 116          */
 117         mcpm_cpu_suspend(0);
 118
 119         /* return value != 0 means failure */
 120         return 1;
 121 }
 122
 123 /**
 124  * bl_enter_powerdown - Programs CPU to enter the specified state
 125  * @dev: cpuidle device
 126  * @drv: The target state to be programmed
 127  * @idx: state index
 128  *
 129  * Called from the CPUidle framework to program the device to the
 130  * specified target state selected by the governor.
 131  */
 132 static int bl_enter_powerdown(struct cpuidle_device *dev,
 133                                 struct cpuidle_driver *drv, int idx)
 134 {
 135         cpu_pm_enter();
 136
 137         cpu_suspend(0, bl_powerdown_finisher);
 138
 139         /* signals the MCPM core that CPU is out of low power state */
 140         mcpm_cpu_powered_up();
 141
 142         cpu_pm_exit();
 143
 144         return idx;
 145 }
 146
 147 static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int part_id)
 148 {
 149         struct cpumask *cpumask;
 150         int cpu;
 151
 152         cpumask = kzalloc(cpumask_size(), GFP_KERNEL);
 153         if (!cpumask)
 154                 return -ENOMEM;
 155
 156         for_each_possible_cpu(cpu)
 157                 if (smp_cpuid_part(cpu) == part_id)
 158                         cpumask_set_cpu(cpu, cpumask);
 159
 160         drv->cpumask = cpumask;
 161
 162         return 0;
 163 }
 164
 165 static const struct of_device_id compatible_machine_match[] = {
 166         { .compatible = "arm,vexpress,v2p-ca15_a7" },
 167         { .compatible = "samsung,exynos5420" },
 168         { .compatible = "samsung,exynos5800" },
 169         {},
 170 };
 171
 172 static int __init bl_idle_init(void)
 173 {
 174         int ret;
 175         struct device_node *root = of_find_node_by_path("/");
 176
 177         if (!root)
 178                 return -ENODEV;
 179
 180         /*
 181          * Initialize the driver just for a compliant set of machines
 182          */
 183         if (!of_match_node(compatible_machine_match, root))
 184                 return -ENODEV;
 185         /*
 186          * For now the differentiation between little and big cores
 187          * is based on the part number. A7 cores are considered little
 188          * cores, A15 are considered big cores. This distinction may
 189          * evolve in the future with a more generic matching approach.
 190          */
 191         ret = bl_idle_driver_init(&bl_idle_little_driver,
 192                                   ARM_CPU_PART_CORTEX_A7);
 193         if (ret)
 194                 return ret;
 195
 196         ret = bl_idle_driver_init(&bl_idle_big_driver, ARM_CPU_PART_CORTEX_A15);
 197         if (ret)
 198                 goto out_uninit_little;
 199
 200         /* Start at index 1, index 0 standard WFI */
 201         ret = dt_init_idle_driver(&bl_idle_big_driver, bl_idle_state_match, 1);
 202         if (ret < 0)
 203                 goto out_uninit_big;
 204
 205         /* Start at index 1, index 0 standard WFI */
 206         ret = dt_init_idle_driver(&bl_idle_little_driver,
 207                                   bl_idle_state_match, 1);
 208         if (ret < 0)
 209                 goto out_uninit_big;
 210
 211         ret = cpuidle_register(&bl_idle_little_driver, NULL);
 212         if (ret)
 213                 goto out_uninit_big;
 214
 215         ret = cpuidle_register(&bl_idle_big_driver, NULL);
 216         if (ret)
 217                 goto out_unregister_little;
 218
 219         return 0;
 220
 221 out_unregister_little:
 222         cpuidle_unregister(&bl_idle_little_driver);
 223 out_uninit_big:
 224         kfree(bl_idle_big_driver.cpumask);
 225 out_uninit_little:
 226         kfree(bl_idle_little_driver.cpumask);
 227
 228         return ret;
 229 }
 230 device_initcall(bl_idle_init);