1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Azoteq IQS620A PWM Generator 4 * 5 * Copyright (C) 2019 Jeff LaBundy <jeff@labundy.com> 6 * 7 * Limitations: 8 * - The period is fixed to 1 ms and is generated continuously despite changes 9 * to the duty cycle or enable/disable state. 10 * - Changes to the duty cycle or enable/disable state take effect immediately 11 * and may result in a glitch during the period in which the change is made. 12 * - The device cannot generate a 0% duty cycle. For duty cycles below 1 / 256 13 * ms, the output is disabled and relies upon an external pull-down resistor 14 * to hold the GPIO3/LTX pin low. 15 */ 16 17 #include <linux/device.h> 18 #include <linux/kernel.h> 19 #include <linux/mfd/iqs62x.h> 20 #include <linux/module.h> 21 #include <linux/mutex.h> 22 #include <linux/notifier.h> 23 #include <linux/platform_device.h> 24 #include <linux/pwm.h> 25 #include <linux/regmap.h> 26 #include <linux/slab.h> 27 28 #define IQS620_PWR_SETTINGS 0xD2 29 #define IQS620_PWR_SETTINGS_PWM_OUT BIT(7) 30 31 #define IQS620_PWM_DUTY_CYCLE 0xD8 32 33 #define IQS620_PWM_PERIOD_NS 1000000 34 35 struct iqs620_pwm_private { 36 struct iqs62x_core *iqs62x; 37 struct pwm_chip chip; 38 struct notifier_block notifier; 39 struct mutex lock; 40 bool out_en; 41 u8 duty_val; 42 }; 43 44 static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, 45 const struct pwm_state *state) 46 { 47 struct iqs620_pwm_private *iqs620_pwm; 48 struct iqs62x_core *iqs62x; 49 int duty_scale, ret; 50 51 if (state->polarity != PWM_POLARITY_NORMAL) 52 return -ENOTSUPP; 53 54 if (state->period < IQS620_PWM_PERIOD_NS) 55 return -EINVAL; 56 57 iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); 58 iqs62x = iqs620_pwm->iqs62x; 59 60 /* 61 * The duty cycle generated by the device is calculated as follows: 62 * 63 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms 64 * 65 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255 66 * (inclusive). Therefore the lowest duty cycle the device can generate 67 * while the output is enabled is 1 / 256 ms. 68 * 69 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to 70 * allow an external pull-down resistor to hold the GPIO3/LTX pin low. 71 */ 72 duty_scale = state->duty_cycle * 256 / IQS620_PWM_PERIOD_NS; 73 74 mutex_lock(&iqs620_pwm->lock); 75 76 if (!state->enabled || !duty_scale) { 77 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 78 IQS620_PWR_SETTINGS_PWM_OUT, 0); 79 if (ret) 80 goto err_mutex; 81 } 82 83 if (duty_scale) { 84 u8 duty_val = min(duty_scale - 1, 0xFF); 85 86 ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, 87 duty_val); 88 if (ret) 89 goto err_mutex; 90 91 iqs620_pwm->duty_val = duty_val; 92 } 93 94 if (state->enabled && duty_scale) { 95 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 96 IQS620_PWR_SETTINGS_PWM_OUT, 0xFF); 97 if (ret) 98 goto err_mutex; 99 } 100 101 iqs620_pwm->out_en = state->enabled; 102 103 err_mutex: 104 mutex_unlock(&iqs620_pwm->lock); 105 106 return ret; 107 } 108 109 static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, 110 struct pwm_state *state) 111 { 112 struct iqs620_pwm_private *iqs620_pwm; 113 114 iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); 115 116 mutex_lock(&iqs620_pwm->lock); 117 118 /* 119 * Since the device cannot generate a 0% duty cycle, requests to do so 120 * cause subsequent calls to iqs620_pwm_get_state to report the output 121 * as disabled with duty cycle equal to that which was in use prior to 122 * the request. This is not ideal, but is the best compromise based on 123 * the capabilities of the device. 124 */ 125 state->enabled = iqs620_pwm->out_en; 126 state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) * 127 IQS620_PWM_PERIOD_NS, 256); 128 129 mutex_unlock(&iqs620_pwm->lock); 130 131 state->period = IQS620_PWM_PERIOD_NS; 132 } 133 134 static int iqs620_pwm_notifier(struct notifier_block *notifier, 135 unsigned long event_flags, void *context) 136 { 137 struct iqs620_pwm_private *iqs620_pwm; 138 struct iqs62x_core *iqs62x; 139 int ret; 140 141 if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET))) 142 return NOTIFY_DONE; 143 144 iqs620_pwm = container_of(notifier, struct iqs620_pwm_private, 145 notifier); 146 iqs62x = iqs620_pwm->iqs62x; 147 148 mutex_lock(&iqs620_pwm->lock); 149 150 /* 151 * The parent MFD driver already prints an error message in the event 152 * of a device reset, so nothing else is printed here unless there is 153 * an additional failure. 154 */ 155 ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, 156 iqs620_pwm->duty_val); 157 if (ret) 158 goto err_mutex; 159 160 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 161 IQS620_PWR_SETTINGS_PWM_OUT, 162 iqs620_pwm->out_en ? 0xFF : 0); 163 164 err_mutex: 165 mutex_unlock(&iqs620_pwm->lock); 166 167 if (ret) { 168 dev_err(iqs620_pwm->chip.dev, 169 "Failed to re-initialize device: %d\n", ret); 170 return NOTIFY_BAD; 171 } 172 173 return NOTIFY_OK; 174 } 175 176 static const struct pwm_ops iqs620_pwm_ops = { 177 .apply = iqs620_pwm_apply, 178 .get_state = iqs620_pwm_get_state, 179 .owner = THIS_MODULE, 180 }; 181 182 static void iqs620_pwm_notifier_unregister(void *context) 183 { 184 struct iqs620_pwm_private *iqs620_pwm = context; 185 int ret; 186 187 ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh, 188 &iqs620_pwm->notifier); 189 if (ret) 190 dev_err(iqs620_pwm->chip.dev, 191 "Failed to unregister notifier: %d\n", ret); 192 } 193 194 static int iqs620_pwm_probe(struct platform_device *pdev) 195 { 196 struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent); 197 struct iqs620_pwm_private *iqs620_pwm; 198 unsigned int val; 199 int ret; 200 201 iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL); 202 if (!iqs620_pwm) 203 return -ENOMEM; 204 205 platform_set_drvdata(pdev, iqs620_pwm); 206 iqs620_pwm->iqs62x = iqs62x; 207 208 ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val); 209 if (ret) 210 return ret; 211 iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT; 212 213 ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val); 214 if (ret) 215 return ret; 216 iqs620_pwm->duty_val = val; 217 218 iqs620_pwm->chip.dev = &pdev->dev; 219 iqs620_pwm->chip.ops = &iqs620_pwm_ops; 220 iqs620_pwm->chip.base = -1; 221 iqs620_pwm->chip.npwm = 1; 222 223 mutex_init(&iqs620_pwm->lock); 224 225 iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier; 226 ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh, 227 &iqs620_pwm->notifier); 228 if (ret) { 229 dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret); 230 return ret; 231 } 232 233 ret = devm_add_action_or_reset(&pdev->dev, 234 iqs620_pwm_notifier_unregister, 235 iqs620_pwm); 236 if (ret) 237 return ret; 238 239 ret = pwmchip_add(&iqs620_pwm->chip); 240 if (ret) 241 dev_err(&pdev->dev, "Failed to add device: %d\n", ret); 242 243 return ret; 244 } 245 246 static int iqs620_pwm_remove(struct platform_device *pdev) 247 { 248 struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev); 249 int ret; 250 251 ret = pwmchip_remove(&iqs620_pwm->chip); 252 if (ret) 253 dev_err(&pdev->dev, "Failed to remove device: %d\n", ret); 254 255 return ret; 256 } 257 258 static struct platform_driver iqs620_pwm_platform_driver = { 259 .driver = { 260 .name = "iqs620a-pwm", 261 }, 262 .probe = iqs620_pwm_probe, 263 .remove = iqs620_pwm_remove, 264 }; 265 module_platform_driver(iqs620_pwm_platform_driver); 266 267 MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>"); 268 MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator"); 269 MODULE_LICENSE("GPL"); 270 MODULE_ALIAS("platform:iqs620a-pwm"); 271