1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/drivers/devfreq/governor_passive.c 4 * 5 * Copyright (C) 2016 Samsung Electronics 6 * Author: Chanwoo Choi <cw00.choi@samsung.com> 7 * Author: MyungJoo Ham <myungjoo.ham@samsung.com> 8 */ 9 10 #include <linux/module.h> 11 #include <linux/device.h> 12 #include <linux/devfreq.h> 13 #include "governor.h" 14 15 static int devfreq_passive_get_target_freq(struct devfreq *devfreq, 16 unsigned long *freq) 17 { 18 struct devfreq_passive_data *p_data 19 = (struct devfreq_passive_data *)devfreq->data; 20 struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent; 21 unsigned long child_freq = ULONG_MAX; 22 struct dev_pm_opp *opp; 23 int i, count, ret = 0; 24 25 /* 26 * If the devfreq device with passive governor has the specific method 27 * to determine the next frequency, should use the get_target_freq() 28 * of struct devfreq_passive_data. 29 */ 30 if (p_data->get_target_freq) { 31 ret = p_data->get_target_freq(devfreq, freq); 32 goto out; 33 } 34 35 /* 36 * If the parent and passive devfreq device uses the OPP table, 37 * get the next frequency by using the OPP table. 38 */ 39 40 /* 41 * - parent devfreq device uses the governors except for passive. 42 * - passive devfreq device uses the passive governor. 43 * 44 * Each devfreq has the OPP table. After deciding the new frequency 45 * from the governor of parent devfreq device, the passive governor 46 * need to get the index of new frequency on OPP table of parent 47 * device. And then the index is used for getting the suitable 48 * new frequency for passive devfreq device. 49 */ 50 if (!devfreq->profile || !devfreq->profile->freq_table 51 || devfreq->profile->max_state <= 0) 52 return -EINVAL; 53 54 /* 55 * The passive governor have to get the correct frequency from OPP 56 * list of parent device. Because in this case, *freq is temporary 57 * value which is decided by ondemand governor. 58 */ 59 opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0); 60 if (IS_ERR(opp)) { 61 ret = PTR_ERR(opp); 62 goto out; 63 } 64 65 dev_pm_opp_put(opp); 66 67 /* 68 * Get the OPP table's index of decided freqeuncy by governor 69 * of parent device. 70 */ 71 for (i = 0; i < parent_devfreq->profile->max_state; i++) 72 if (parent_devfreq->profile->freq_table[i] == *freq) 73 break; 74 75 if (i == parent_devfreq->profile->max_state) { 76 ret = -EINVAL; 77 goto out; 78 } 79 80 /* Get the suitable frequency by using index of parent device. */ 81 if (i < devfreq->profile->max_state) { 82 child_freq = devfreq->profile->freq_table[i]; 83 } else { 84 count = devfreq->profile->max_state; 85 child_freq = devfreq->profile->freq_table[count - 1]; 86 } 87 88 /* Return the suitable frequency for passive device. */ 89 *freq = child_freq; 90 91 out: 92 return ret; 93 } 94 95 static int devfreq_passive_notifier_call(struct notifier_block *nb, 96 unsigned long event, void *ptr) 97 { 98 struct devfreq_passive_data *data 99 = container_of(nb, struct devfreq_passive_data, nb); 100 struct devfreq *devfreq = (struct devfreq *)data->this; 101 struct devfreq *parent = (struct devfreq *)data->parent; 102 struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr; 103 unsigned long freq = freqs->new; 104 int ret = 0; 105 106 mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING); 107 switch (event) { 108 case DEVFREQ_PRECHANGE: 109 if (parent->previous_freq > freq) 110 ret = devfreq_update_target(devfreq, freq); 111 112 break; 113 case DEVFREQ_POSTCHANGE: 114 if (parent->previous_freq < freq) 115 ret = devfreq_update_target(devfreq, freq); 116 break; 117 } 118 mutex_unlock(&devfreq->lock); 119 120 if (ret < 0) 121 dev_warn(&devfreq->dev, 122 "failed to update devfreq using passive governor\n"); 123 124 return NOTIFY_DONE; 125 } 126 127 static int devfreq_passive_event_handler(struct devfreq *devfreq, 128 unsigned int event, void *data) 129 { 130 struct devfreq_passive_data *p_data 131 = (struct devfreq_passive_data *)devfreq->data; 132 struct devfreq *parent = (struct devfreq *)p_data->parent; 133 struct notifier_block *nb = &p_data->nb; 134 int ret = 0; 135 136 if (!parent) 137 return -EPROBE_DEFER; 138 139 switch (event) { 140 case DEVFREQ_GOV_START: 141 if (!p_data->this) 142 p_data->this = devfreq; 143 144 nb->notifier_call = devfreq_passive_notifier_call; 145 ret = devfreq_register_notifier(parent, nb, 146 DEVFREQ_TRANSITION_NOTIFIER); 147 break; 148 case DEVFREQ_GOV_STOP: 149 WARN_ON(devfreq_unregister_notifier(parent, nb, 150 DEVFREQ_TRANSITION_NOTIFIER)); 151 break; 152 default: 153 break; 154 } 155 156 return ret; 157 } 158 159 static struct devfreq_governor devfreq_passive = { 160 .name = DEVFREQ_GOV_PASSIVE, 161 .flags = DEVFREQ_GOV_FLAG_IMMUTABLE, 162 .get_target_freq = devfreq_passive_get_target_freq, 163 .event_handler = devfreq_passive_event_handler, 164 }; 165 166 static int __init devfreq_passive_init(void) 167 { 168 return devfreq_add_governor(&devfreq_passive); 169 } 170 subsys_initcall(devfreq_passive_init); 171 172 static void __exit devfreq_passive_exit(void) 173 { 174 int ret; 175 176 ret = devfreq_remove_governor(&devfreq_passive); 177 if (ret) 178 pr_err("%s: failed remove governor %d\n", __func__, ret); 179 } 180 module_exit(devfreq_passive_exit); 181 182 MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>"); 183 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>"); 184 MODULE_DESCRIPTION("DEVFREQ Passive governor"); 185 MODULE_LICENSE("GPL v2"); 186