1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  Copyright (C) 2019 Linaro Limited.
  4 *
  5 *  Author: Daniel Lezcano <daniel.lezcano@linaro.org>
  6 *
  7 */
  8#define pr_fmt(fmt) "cpuidle cooling: " fmt
  9
 10#include <linux/cpu_cooling.h>
 11#include <linux/cpuidle.h>
 12#include <linux/err.h>
 13#include <linux/idle_inject.h>
 14#include <linux/idr.h>
 15#include <linux/of_device.h>
 16#include <linux/slab.h>
 17#include <linux/thermal.h>
 18
 19/**
 20 * struct cpuidle_cooling_device - data for the idle cooling device
 21 * @ii_dev: an atomic to keep track of the last task exiting the idle cycle
 22 * @state: a normalized integer giving the state of the cooling device
 23 */
 24struct cpuidle_cooling_device {
 25	struct idle_inject_device *ii_dev;
 26	unsigned long state;
 27};
 28
 29static DEFINE_IDA(cpuidle_ida);
 30
 31/**
 32 * cpuidle_cooling_runtime - Running time computation
 33 * @idle_duration_us: the idle cooling device
 34 * @state: a percentile based number
 35 *
 36 * The running duration is computed from the idle injection duration
 37 * which is fixed. If we reach 100% of idle injection ratio, that
 38 * means the running duration is zero. If we have a 50% ratio
 39 * injection, that means we have equal duration for idle and for
 40 * running duration.
 41 *
 42 * The formula is deduced as follows:
 43 *
 44 *  running = idle x ((100 / ratio) - 1)
 45 *
 46 * For precision purpose for integer math, we use the following:
 47 *
 48 *  running = (idle x 100) / ratio - idle
 49 *
 50 * For example, if we have an injected duration of 50%, then we end up
 51 * with 10ms of idle injection and 10ms of running duration.
 52 *
 53 * Return: An unsigned int for a usec based runtime duration.
 54 */
 55static unsigned int cpuidle_cooling_runtime(unsigned int idle_duration_us,
 56					    unsigned long state)
 57{
 58	if (!state)
 59		return 0;
 60
 61	return ((idle_duration_us * 100) / state) - idle_duration_us;
 62}
 63
 64/**
 65 * cpuidle_cooling_get_max_state - Get the maximum state
 66 * @cdev  : the thermal cooling device
 67 * @state : a pointer to the state variable to be filled
 68 *
 69 * The function always returns 100 as the injection ratio. It is
 70 * percentile based for consistency accross different platforms.
 71 *
 72 * Return: The function can not fail, it is always zero
 73 */
 74static int cpuidle_cooling_get_max_state(struct thermal_cooling_device *cdev,
 75					 unsigned long *state)
 76{
 77	/*
 78	 * Depending on the configuration or the hardware, the running
 79	 * cycle and the idle cycle could be different. We want to
 80	 * unify that to an 0..100 interval, so the set state
 81	 * interface will be the same whatever the platform is.
 82	 *
 83	 * The state 100% will make the cluster 100% ... idle. A 0%
 84	 * injection ratio means no idle injection at all and 50%
 85	 * means for 10ms of idle injection, we have 10ms of running
 86	 * time.
 87	 */
 88	*state = 100;
 89
 90	return 0;
 91}
 92
 93/**
 94 * cpuidle_cooling_get_cur_state - Get the current cooling state
 95 * @cdev: the thermal cooling device
 96 * @state: a pointer to the state
 97 *
 98 * The function just copies  the state value from the private thermal
 99 * cooling device structure, the mapping is 1 <-> 1.
100 *
101 * Return: The function can not fail, it is always zero
102 */
103static int cpuidle_cooling_get_cur_state(struct thermal_cooling_device *cdev,
104					 unsigned long *state)
105{
106	struct cpuidle_cooling_device *idle_cdev = cdev->devdata;
107
108	*state = idle_cdev->state;
109
110	return 0;
111}
112
113/**
114 * cpuidle_cooling_set_cur_state - Set the current cooling state
115 * @cdev: the thermal cooling device
116 * @state: the target state
117 *
118 * The function checks first if we are initiating the mitigation which
119 * in turn wakes up all the idle injection tasks belonging to the idle
120 * cooling device. In any case, it updates the internal state for the
121 * cooling device.
122 *
123 * Return: The function can not fail, it is always zero
124 */
125static int cpuidle_cooling_set_cur_state(struct thermal_cooling_device *cdev,
126					 unsigned long state)
127{
128	struct cpuidle_cooling_device *idle_cdev = cdev->devdata;
129	struct idle_inject_device *ii_dev = idle_cdev->ii_dev;
130	unsigned long current_state = idle_cdev->state;
131	unsigned int runtime_us, idle_duration_us;
132
133	idle_cdev->state = state;
134
135	idle_inject_get_duration(ii_dev, &runtime_us, &idle_duration_us);
136
137	runtime_us = cpuidle_cooling_runtime(idle_duration_us, state);
138
139	idle_inject_set_duration(ii_dev, runtime_us, idle_duration_us);
140
141	if (current_state == 0 && state > 0) {
142		idle_inject_start(ii_dev);
143	} else if (current_state > 0 && !state)  {
144		idle_inject_stop(ii_dev);
145	}
146
147	return 0;
148}
149
150/**
151 * cpuidle_cooling_ops - thermal cooling device ops
152 */
153static struct thermal_cooling_device_ops cpuidle_cooling_ops = {
154	.get_max_state = cpuidle_cooling_get_max_state,
155	.get_cur_state = cpuidle_cooling_get_cur_state,
156	.set_cur_state = cpuidle_cooling_set_cur_state,
157};
158
159/**
160 * __cpuidle_cooling_register: register the cooling device
161 * @drv: a cpuidle driver structure pointer
162 * @np: a device node structure pointer used for the thermal binding
163 *
164 * This function is in charge of allocating the cpuidle cooling device
165 * structure, the idle injection, initialize them and register the
166 * cooling device to the thermal framework.
167 *
168 * Return: zero on success, a negative value returned by one of the
169 * underlying subsystem in case of error
170 */
171static int __cpuidle_cooling_register(struct device_node *np,
172				      struct cpuidle_driver *drv)
173{
174	struct idle_inject_device *ii_dev;
175	struct cpuidle_cooling_device *idle_cdev;
176	struct thermal_cooling_device *cdev;
177	unsigned int idle_duration_us = TICK_USEC;
178	unsigned int latency_us = UINT_MAX;
179	char dev_name[THERMAL_NAME_LENGTH];
180	int id, ret;
181
182	idle_cdev = kzalloc(sizeof(*idle_cdev), GFP_KERNEL);
183	if (!idle_cdev) {
184		ret = -ENOMEM;
185		goto out;
186	}
187
188	id = ida_simple_get(&cpuidle_ida, 0, 0, GFP_KERNEL);
189	if (id < 0) {
190		ret = id;
191		goto out_kfree;
192	}
193
194	ii_dev = idle_inject_register(drv->cpumask);
195	if (!ii_dev) {
196		ret = -EINVAL;
197		goto out_id;
198	}
199
200	of_property_read_u32(np, "duration-us", &idle_duration_us);
201	of_property_read_u32(np, "exit-latency-us", &latency_us);
202
203	idle_inject_set_duration(ii_dev, TICK_USEC, idle_duration_us);
204	idle_inject_set_latency(ii_dev, latency_us);
205
206	idle_cdev->ii_dev = ii_dev;
207
208	snprintf(dev_name, sizeof(dev_name), "thermal-idle-%d", id);
209
210	cdev = thermal_of_cooling_device_register(np, dev_name, idle_cdev,
211						  &cpuidle_cooling_ops);
212	if (IS_ERR(cdev)) {
213		ret = PTR_ERR(cdev);
214		goto out_unregister;
215	}
216
217	pr_debug("%s: Idle injection set with idle duration=%u, latency=%u\n",
218		 dev_name, idle_duration_us, latency_us);
219
220	return 0;
221
222out_unregister:
223	idle_inject_unregister(ii_dev);
224out_id:
225	ida_simple_remove(&cpuidle_ida, id);
226out_kfree:
227	kfree(idle_cdev);
228out:
229	return ret;
230}
231
232/**
233 * cpuidle_cooling_register - Idle cooling device initialization function
234 * @drv: a cpuidle driver structure pointer
235 *
236 * This function is in charge of creating a cooling device per cpuidle
237 * driver and register it to the thermal framework.
238 *
239 * Return: zero on success, or negative value corresponding to the
240 * error detected in the underlying subsystems.
241 */
242void cpuidle_cooling_register(struct cpuidle_driver *drv)
243{
244	struct device_node *cooling_node;
245	struct device_node *cpu_node;
246	int cpu, ret;
247
248	for_each_cpu(cpu, drv->cpumask) {
249
250		cpu_node = of_cpu_device_node_get(cpu);
251
252		cooling_node = of_get_child_by_name(cpu_node, "thermal-idle");
253
254		of_node_put(cpu_node);
255
256		if (!cooling_node) {
257			pr_debug("'thermal-idle' node not found for cpu%d\n", cpu);
258			continue;
259		}
260
261		ret = __cpuidle_cooling_register(cooling_node, drv);
262
263		of_node_put(cooling_node);
264
265		if (ret) {
266			pr_err("Failed to register the cpuidle cooling device" \
267			       "for cpu%d: %d\n", cpu, ret);
268			break;
269		}
270	}
271}