1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/drivers/leds-pwm.c 4 * 5 * simple PWM based LED control 6 * 7 * Copyright 2009 Luotao Fu @ Pengutronix (l.fu@pengutronix.de) 8 * 9 * based on leds-gpio.c by Raphael Assenat <raph@8d.com> 10 */ 11 12 #include <linux/module.h> 13 #include <linux/kernel.h> 14 #include <linux/platform_device.h> 15 #include <linux/of.h> 16 #include <linux/leds.h> 17 #include <linux/err.h> 18 #include <linux/pwm.h> 19 #include <linux/slab.h> 20 #include "leds.h" 21 22 struct led_pwm { 23 const char *name; 24 u8 active_low; 25 u8 default_state; 26 unsigned int max_brightness; 27 }; 28 29 struct led_pwm_data { 30 struct led_classdev cdev; 31 struct pwm_device *pwm; 32 struct pwm_state pwmstate; 33 unsigned int active_low; 34 }; 35 36 struct led_pwm_priv { 37 int num_leds; 38 struct led_pwm_data leds[]; 39 }; 40 41 static int led_pwm_set(struct led_classdev *led_cdev, 42 enum led_brightness brightness) 43 { 44 struct led_pwm_data *led_dat = 45 container_of(led_cdev, struct led_pwm_data, cdev); 46 unsigned int max = led_dat->cdev.max_brightness; 47 unsigned long long duty = led_dat->pwmstate.period; 48 49 duty *= brightness; 50 do_div(duty, max); 51 52 if (led_dat->active_low) 53 duty = led_dat->pwmstate.period - duty; 54 55 led_dat->pwmstate.duty_cycle = duty; 56 /* 57 * Disabling a PWM doesn't guarantee that it emits the inactive level. 58 * So keep it on. Only for suspending the PWM should be disabled because 59 * otherwise it refuses to suspend. The possible downside is that the 60 * LED might stay (or even go) on. 61 */ 62 led_dat->pwmstate.enabled = !(led_cdev->flags & LED_SUSPENDED); 63 return pwm_apply_might_sleep(led_dat->pwm, &led_dat->pwmstate); 64 } 65 66 __attribute__((nonnull)) 67 static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv, 68 struct led_pwm *led, struct fwnode_handle *fwnode) 69 { 70 struct led_pwm_data *led_data = &priv->leds[priv->num_leds]; 71 struct led_init_data init_data = { .fwnode = fwnode }; 72 int ret; 73 74 led_data->active_low = led->active_low; 75 led_data->cdev.name = led->name; 76 led_data->cdev.brightness = LED_OFF; 77 led_data->cdev.max_brightness = led->max_brightness; 78 led_data->cdev.flags = LED_CORE_SUSPENDRESUME; 79 80 led_data->pwm = devm_fwnode_pwm_get(dev, fwnode, NULL); 81 if (IS_ERR(led_data->pwm)) 82 return dev_err_probe(dev, PTR_ERR(led_data->pwm), 83 "unable to request PWM for %s\n", 84 led->name); 85 86 led_data->cdev.brightness_set_blocking = led_pwm_set; 87 88 /* init PWM state */ 89 switch (led->default_state) { 90 case LEDS_DEFSTATE_KEEP: 91 pwm_get_state(led_data->pwm, &led_data->pwmstate); 92 if (led_data->pwmstate.period) 93 break; 94 led->default_state = LEDS_DEFSTATE_OFF; 95 dev_warn(dev, 96 "failed to read period for %s, default to off", 97 led->name); 98 fallthrough; 99 default: 100 pwm_init_state(led_data->pwm, &led_data->pwmstate); 101 break; 102 } 103 104 /* set brightness */ 105 switch (led->default_state) { 106 case LEDS_DEFSTATE_ON: 107 led_data->cdev.brightness = led->max_brightness; 108 break; 109 case LEDS_DEFSTATE_KEEP: 110 { 111 uint64_t brightness; 112 113 brightness = led->max_brightness; 114 brightness *= led_data->pwmstate.duty_cycle; 115 do_div(brightness, led_data->pwmstate.period); 116 led_data->cdev.brightness = brightness; 117 } 118 break; 119 } 120 121 ret = devm_led_classdev_register_ext(dev, &led_data->cdev, &init_data); 122 if (ret) { 123 dev_err(dev, "failed to register PWM led for %s: %d\n", 124 led->name, ret); 125 return ret; 126 } 127 128 if (led->default_state != LEDS_DEFSTATE_KEEP) { 129 ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness); 130 if (ret) { 131 dev_err(dev, "failed to set led PWM value for %s: %d", 132 led->name, ret); 133 return ret; 134 } 135 } 136 137 priv->num_leds++; 138 return 0; 139 } 140 141 static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv) 142 { 143 struct fwnode_handle *fwnode; 144 struct led_pwm led; 145 int ret; 146 147 device_for_each_child_node(dev, fwnode) { 148 memset(&led, 0, sizeof(led)); 149 150 ret = fwnode_property_read_string(fwnode, "label", &led.name); 151 if (ret && is_of_node(fwnode)) 152 led.name = to_of_node(fwnode)->name; 153 154 if (!led.name) { 155 ret = -EINVAL; 156 goto err_child_out; 157 } 158 159 led.active_low = fwnode_property_read_bool(fwnode, 160 "active-low"); 161 fwnode_property_read_u32(fwnode, "max-brightness", 162 &led.max_brightness); 163 164 led.default_state = led_init_default_state_get(fwnode); 165 166 ret = led_pwm_add(dev, priv, &led, fwnode); 167 if (ret) 168 goto err_child_out; 169 } 170 171 return 0; 172 173 err_child_out: 174 fwnode_handle_put(fwnode); 175 return ret; 176 } 177 178 static int led_pwm_probe(struct platform_device *pdev) 179 { 180 struct led_pwm_priv *priv; 181 int ret = 0; 182 int count; 183 184 count = device_get_child_node_count(&pdev->dev); 185 186 if (!count) 187 return -EINVAL; 188 189 priv = devm_kzalloc(&pdev->dev, struct_size(priv, leds, count), 190 GFP_KERNEL); 191 if (!priv) 192 return -ENOMEM; 193 194 ret = led_pwm_create_fwnode(&pdev->dev, priv); 195 196 if (ret) 197 return ret; 198 199 platform_set_drvdata(pdev, priv); 200 201 return 0; 202 } 203 204 static const struct of_device_id of_pwm_leds_match[] = { 205 { .compatible = "pwm-leds", }, 206 {}, 207 }; 208 MODULE_DEVICE_TABLE(of, of_pwm_leds_match); 209 210 static struct platform_driver led_pwm_driver = { 211 .probe = led_pwm_probe, 212 .driver = { 213 .name = "leds_pwm", 214 .of_match_table = of_pwm_leds_match, 215 }, 216 }; 217 218 module_platform_driver(led_pwm_driver); 219 220 MODULE_AUTHOR("Luotao Fu <l.fu@pengutronix.de>"); 221 MODULE_DESCRIPTION("generic PWM LED driver"); 222 MODULE_LICENSE("GPL v2"); 223 MODULE_ALIAS("platform:leds-pwm"); 224