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 */
bl_powerdown_finisher(unsigned long arg)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 mcpm_cpu_suspend();
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 */
bl_enter_powerdown(struct cpuidle_device * dev,struct cpuidle_driver * drv,int idx)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
bl_idle_driver_init(struct cpuidle_driver * drv,int part_id)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 { .compatible = "samsung,exynos5800" },
163 {},
164 };
165
bl_idle_init(void)166 static int __init bl_idle_init(void)
167 {
168 int ret;
169 struct device_node *root = of_find_node_by_path("/");
170
171 if (!root)
172 return -ENODEV;
173
174 /*
175 * Initialize the driver just for a compliant set of machines
176 */
177 if (!of_match_node(compatible_machine_match, root))
178 return -ENODEV;
179
180 if (!mcpm_is_available())
181 return -EUNATCH;
182
183 /*
184 * For now the differentiation between little and big cores
185 * is based on the part number. A7 cores are considered little
186 * cores, A15 are considered big cores. This distinction may
187 * evolve in the future with a more generic matching approach.
188 */
189 ret = bl_idle_driver_init(&bl_idle_little_driver,
190 ARM_CPU_PART_CORTEX_A7);
191 if (ret)
192 return ret;
193
194 ret = bl_idle_driver_init(&bl_idle_big_driver, ARM_CPU_PART_CORTEX_A15);
195 if (ret)
196 goto out_uninit_little;
197
198 /* Start at index 1, index 0 standard WFI */
199 ret = dt_init_idle_driver(&bl_idle_big_driver, bl_idle_state_match, 1);
200 if (ret < 0)
201 goto out_uninit_big;
202
203 /* Start at index 1, index 0 standard WFI */
204 ret = dt_init_idle_driver(&bl_idle_little_driver,
205 bl_idle_state_match, 1);
206 if (ret < 0)
207 goto out_uninit_big;
208
209 ret = cpuidle_register(&bl_idle_little_driver, NULL);
210 if (ret)
211 goto out_uninit_big;
212
213 ret = cpuidle_register(&bl_idle_big_driver, NULL);
214 if (ret)
215 goto out_unregister_little;
216
217 return 0;
218
219 out_unregister_little:
220 cpuidle_unregister(&bl_idle_little_driver);
221 out_uninit_big:
222 kfree(bl_idle_big_driver.cpumask);
223 out_uninit_little:
224 kfree(bl_idle_little_driver.cpumask);
225
226 return ret;
227 }
228 device_initcall(bl_idle_init);
229
