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 part_id) 142 { 143 struct cpumask *cpumask; 144 int cpu; 145 146 cpumask = kzalloc(cpumask_size(), GFP_KERNEL); 147 if (!cpumask) 148 return -ENOMEM; 149 150 for_each_possible_cpu(cpu) 151 if (smp_cpuid_part(cpu) == part_id) 152 cpumask_set_cpu(cpu, cpumask); 153 154 drv->cpumask = cpumask; 155 156 return 0; 157 } 158 159 static const struct of_device_id compatible_machine_match[] = { 160 { .compatible = "arm,vexpress,v2p-ca15_a7" }, 161 { .compatible = "samsung,exynos5420" }, 162 {}, 163 }; 164 165 static int __init bl_idle_init(void) 166 { 167 int ret; 168 struct device_node *root = of_find_node_by_path("/"); 169 170 if (!root) 171 return -ENODEV; 172 173 /* 174 * Initialize the driver just for a compliant set of machines 175 */ 176 if (!of_match_node(compatible_machine_match, root)) 177 return -ENODEV; 178 /* 179 * For now the differentiation between little and big cores 180 * is based on the part number. A7 cores are considered little 181 * cores, A15 are considered big cores. This distinction may 182 * evolve in the future with a more generic matching approach. 183 */ 184 ret = bl_idle_driver_init(&bl_idle_little_driver, 185 ARM_CPU_PART_CORTEX_A7); 186 if (ret) 187 return ret; 188 189 ret = bl_idle_driver_init(&bl_idle_big_driver, ARM_CPU_PART_CORTEX_A15); 190 if (ret) 191 goto out_uninit_little; 192 193 ret = cpuidle_register(&bl_idle_little_driver, NULL); 194 if (ret) 195 goto out_uninit_big; 196 197 ret = cpuidle_register(&bl_idle_big_driver, NULL); 198 if (ret) 199 goto out_unregister_little; 200 201 return 0; 202 203 out_unregister_little: 204 cpuidle_unregister(&bl_idle_little_driver); 205 out_uninit_big: 206 kfree(bl_idle_big_driver.cpumask); 207 out_uninit_little: 208 kfree(bl_idle_little_driver.cpumask); 209 210 return ret; 211 } 212 device_initcall(bl_idle_init); 213