summaryrefslogtreecommitdiff
path: root/drivers/thermal/cpuidle_cooling.c
blob: f678c1281862fbc6c672a9c79a641858cdfc863a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 2019 Linaro Limited.
 *
 *  Author: Daniel Lezcano <daniel.lezcano@linaro.org>
 *
 */
#define pr_fmt(fmt) "cpuidle cooling: " fmt

#include <linux/cpu.h>
#include <linux/cpu_cooling.h>
#include <linux/cpuidle.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/idle_inject.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/thermal.h>

/**
 * struct cpuidle_cooling_device - data for the idle cooling device
 * @ii_dev: an atomic to keep track of the last task exiting the idle cycle
 * @state: a normalized integer giving the state of the cooling device
 */
struct cpuidle_cooling_device {
	struct idle_inject_device *ii_dev;
	unsigned long state;
};

/**
 * cpuidle_cooling_runtime - Running time computation
 * @idle_duration_us: CPU idle time to inject in microseconds
 * @state: a percentile based number
 *
 * The running duration is computed from the idle injection duration
 * which is fixed. If we reach 100% of idle injection ratio, that
 * means the running duration is zero. If we have a 50% ratio
 * injection, that means we have equal duration for idle and for
 * running duration.
 *
 * The formula is deduced as follows:
 *
 *  running = idle x ((100 / ratio) - 1)
 *
 * For precision purpose for integer math, we use the following:
 *
 *  running = (idle x 100) / ratio - idle
 *
 * For example, if we have an injected duration of 50%, then we end up
 * with 10ms of idle injection and 10ms of running duration.
 *
 * Return: An unsigned int for a usec based runtime duration.
 */
static unsigned int cpuidle_cooling_runtime(unsigned int idle_duration_us,
					    unsigned long state)
{
	if (!state)
		return 0;

	return ((idle_duration_us * 100) / state) - idle_duration_us;
}

/**
 * cpuidle_cooling_get_max_state - Get the maximum state
 * @cdev  : the thermal cooling device
 * @state : a pointer to the state variable to be filled
 *
 * The function always returns 100 as the injection ratio. It is
 * percentile based for consistency across different platforms.
 *
 * Return: The function can not fail, it is always zero
 */
static int cpuidle_cooling_get_max_state(struct thermal_cooling_device *cdev,
					 unsigned long *state)
{
	/*
	 * Depending on the configuration or the hardware, the running
	 * cycle and the idle cycle could be different. We want to
	 * unify that to an 0..100 interval, so the set state
	 * interface will be the same whatever the platform is.
	 *
	 * The state 100% will make the cluster 100% ... idle. A 0%
	 * injection ratio means no idle injection at all and 50%
	 * means for 10ms of idle injection, we have 10ms of running
	 * time.
	 */
	*state = 100;

	return 0;
}

/**
 * cpuidle_cooling_get_cur_state - Get the current cooling state
 * @cdev: the thermal cooling device
 * @state: a pointer to the state
 *
 * The function just copies  the state value from the private thermal
 * cooling device structure, the mapping is 1 <-> 1.
 *
 * Return: The function can not fail, it is always zero
 */
static int cpuidle_cooling_get_cur_state(struct thermal_cooling_device *cdev,
					 unsigned long *state)
{
	struct cpuidle_cooling_device *idle_cdev = cdev->devdata;

	*state = idle_cdev->state;

	return 0;
}

/**
 * cpuidle_cooling_set_cur_state - Set the current cooling state
 * @cdev: the thermal cooling device
 * @state: the target state
 *
 * The function checks first if we are initiating the mitigation which
 * in turn wakes up all the idle injection tasks belonging to the idle
 * cooling device. In any case, it updates the internal state for the
 * cooling device.
 *
 * Return: The function can not fail, it is always zero
 */
static int cpuidle_cooling_set_cur_state(struct thermal_cooling_device *cdev,
					 unsigned long state)
{
	struct cpuidle_cooling_device *idle_cdev = cdev->devdata;
	struct idle_inject_device *ii_dev = idle_cdev->ii_dev;
	unsigned long current_state = idle_cdev->state;
	unsigned int runtime_us, idle_duration_us;

	idle_cdev->state = state;

	idle_inject_get_duration(ii_dev, &runtime_us, &idle_duration_us);

	runtime_us = cpuidle_cooling_runtime(idle_duration_us, state);

	idle_inject_set_duration(ii_dev, runtime_us, idle_duration_us);

	if (current_state == 0 && state > 0) {
		idle_inject_start(ii_dev);
	} else if (current_state > 0 && !state)  {
		idle_inject_stop(ii_dev);
	}

	return 0;
}

/*
 * cpuidle_cooling_ops - thermal cooling device ops
 */
static struct thermal_cooling_device_ops cpuidle_cooling_ops = {
	.get_max_state = cpuidle_cooling_get_max_state,
	.get_cur_state = cpuidle_cooling_get_cur_state,
	.set_cur_state = cpuidle_cooling_set_cur_state,
};

/**
 * __cpuidle_cooling_register: register the cooling device
 * @drv: a cpuidle driver structure pointer
 * @np: a device node structure pointer used for the thermal binding
 *
 * This function is in charge of allocating the cpuidle cooling device
 * structure, the idle injection, initialize them and register the
 * cooling device to the thermal framework.
 *
 * Return: zero on success, a negative value returned by one of the
 * underlying subsystem in case of error
 */
static int __cpuidle_cooling_register(struct device_node *np,
				      struct cpuidle_driver *drv)
{
	struct idle_inject_device *ii_dev;
	struct cpuidle_cooling_device *idle_cdev;
	struct thermal_cooling_device *cdev;
	struct device *dev;
	unsigned int idle_duration_us = TICK_USEC;
	unsigned int latency_us = UINT_MAX;
	char *name;
	int ret;

	idle_cdev = kzalloc(sizeof(*idle_cdev), GFP_KERNEL);
	if (!idle_cdev) {
		ret = -ENOMEM;
		goto out;
	}

	ii_dev = idle_inject_register(drv->cpumask);
	if (!ii_dev) {
		ret = -EINVAL;
		goto out_kfree;
	}

	of_property_read_u32(np, "duration-us", &idle_duration_us);
	of_property_read_u32(np, "exit-latency-us", &latency_us);

	idle_inject_set_duration(ii_dev, TICK_USEC, idle_duration_us);
	idle_inject_set_latency(ii_dev, latency_us);

	idle_cdev->ii_dev = ii_dev;

	dev = get_cpu_device(cpumask_first(drv->cpumask));

	name = kasprintf(GFP_KERNEL, "idle-%s", dev_name(dev));
	if (!name) {
		ret = -ENOMEM;
		goto out_unregister;
	}

	cdev = thermal_of_cooling_device_register(np, name, idle_cdev,
						  &cpuidle_cooling_ops);
	if (IS_ERR(cdev)) {
		ret = PTR_ERR(cdev);
		goto out_kfree_name;
	}

	pr_debug("%s: Idle injection set with idle duration=%u, latency=%u\n",
		 name, idle_duration_us, latency_us);

	kfree(name);

	return 0;

out_kfree_name:
	kfree(name);
out_unregister:
	idle_inject_unregister(ii_dev);
out_kfree:
	kfree(idle_cdev);
out:
	return ret;
}

/**
 * cpuidle_cooling_register - Idle cooling device initialization function
 * @drv: a cpuidle driver structure pointer
 *
 * This function is in charge of creating a cooling device per cpuidle
 * driver and register it to the thermal framework.
 */
void cpuidle_cooling_register(struct cpuidle_driver *drv)
{
	struct device_node *cooling_node;
	struct device_node *cpu_node;
	int cpu, ret;

	for_each_cpu(cpu, drv->cpumask) {

		cpu_node = of_cpu_device_node_get(cpu);

		cooling_node = of_get_child_by_name(cpu_node, "thermal-idle");

		of_node_put(cpu_node);

		if (!cooling_node) {
			pr_debug("'thermal-idle' node not found for cpu%d\n", cpu);
			continue;
		}

		ret = __cpuidle_cooling_register(cooling_node, drv);

		of_node_put(cooling_node);

		if (ret) {
			pr_err("Failed to register the cpuidle cooling device" \
			       "for cpu%d: %d\n", cpu, ret);
			break;
		}
	}
}