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 static 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  */
  60 static 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
  76 static 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  */
  97 static 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  */
 126 static 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
 141 static 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
 166 static 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
 200 out_unregister_little:
 201         cpuidle_unregister(&bl_idle_little_driver);
 202 out_uninit_big:
 203         kfree(bl_idle_big_driver.cpumask);
 204 out_uninit_little:
 205         kfree(bl_idle_little_driver.cpumask);
 206
 207         return ret;
 208 }
 209 device_initcall(bl_idle_init);