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 u64 duty_scale; 50 int ret; 51 52 if (state->polarity != PWM_POLARITY_NORMAL) 53 return -ENOTSUPP; 54 55 if (state->period < IQS620_PWM_PERIOD_NS) 56 return -EINVAL; 57 58 iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); 59 iqs62x = iqs620_pwm->iqs62x; 60 61 /* 62 * The duty cycle generated by the device is calculated as follows: 63 * 64 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms 65 * 66 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255 67 * (inclusive). Therefore the lowest duty cycle the device can generate 68 * while the output is enabled is 1 / 256 ms. 69 * 70 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to 71 * allow an external pull-down resistor to hold the GPIO3/LTX pin low. 72 */ 73 duty_scale = div_u64(state->duty_cycle * 256, IQS620_PWM_PERIOD_NS); 74 75 mutex_lock(&iqs620_pwm->lock); 76 77 if (!state->enabled || !duty_scale) { 78 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 79 IQS620_PWR_SETTINGS_PWM_OUT, 0); 80 if (ret) 81 goto err_mutex; 82 } 83 84 if (duty_scale) { 85 u8 duty_val = min_t(u64, duty_scale - 1, 0xff); 86 87 ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, 88 duty_val); 89 if (ret) 90 goto err_mutex; 91 92 iqs620_pwm->duty_val = duty_val; 93 } 94 95 if (state->enabled && duty_scale) { 96 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 97 IQS620_PWR_SETTINGS_PWM_OUT, 0xff); 98 if (ret) 99 goto err_mutex; 100 } 101 102 iqs620_pwm->out_en = state->enabled; 103 104 err_mutex: 105 mutex_unlock(&iqs620_pwm->lock); 106 107 return ret; 108 } 109 110 static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, 111 struct pwm_state *state) 112 { 113 struct iqs620_pwm_private *iqs620_pwm; 114 115 iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); 116 117 mutex_lock(&iqs620_pwm->lock); 118 119 /* 120 * Since the device cannot generate a 0% duty cycle, requests to do so 121 * cause subsequent calls to iqs620_pwm_get_state to report the output 122 * as disabled with duty cycle equal to that which was in use prior to 123 * the request. This is not ideal, but is the best compromise based on 124 * the capabilities of the device. 125 */ 126 state->enabled = iqs620_pwm->out_en; 127 state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) * 128 IQS620_PWM_PERIOD_NS, 256); 129 130 mutex_unlock(&iqs620_pwm->lock); 131 132 state->period = IQS620_PWM_PERIOD_NS; 133 } 134 135 static int iqs620_pwm_notifier(struct notifier_block *notifier, 136 unsigned long event_flags, void *context) 137 { 138 struct iqs620_pwm_private *iqs620_pwm; 139 struct iqs62x_core *iqs62x; 140 int ret; 141 142 if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET))) 143 return NOTIFY_DONE; 144 145 iqs620_pwm = container_of(notifier, struct iqs620_pwm_private, 146 notifier); 147 iqs62x = iqs620_pwm->iqs62x; 148 149 mutex_lock(&iqs620_pwm->lock); 150 151 /* 152 * The parent MFD driver already prints an error message in the event 153 * of a device reset, so nothing else is printed here unless there is 154 * an additional failure. 155 */ 156 ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, 157 iqs620_pwm->duty_val); 158 if (ret) 159 goto err_mutex; 160 161 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 162 IQS620_PWR_SETTINGS_PWM_OUT, 163 iqs620_pwm->out_en ? 0xff : 0); 164 165 err_mutex: 166 mutex_unlock(&iqs620_pwm->lock); 167 168 if (ret) { 169 dev_err(iqs620_pwm->chip.dev, 170 "Failed to re-initialize device: %d\n", ret); 171 return NOTIFY_BAD; 172 } 173 174 return NOTIFY_OK; 175 } 176 177 static const struct pwm_ops iqs620_pwm_ops = { 178 .apply = iqs620_pwm_apply, 179 .get_state = iqs620_pwm_get_state, 180 .owner = THIS_MODULE, 181 }; 182 183 static void iqs620_pwm_notifier_unregister(void *context) 184 { 185 struct iqs620_pwm_private *iqs620_pwm = context; 186 int ret; 187 188 ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh, 189 &iqs620_pwm->notifier); 190 if (ret) 191 dev_err(iqs620_pwm->chip.dev, 192 "Failed to unregister notifier: %d\n", ret); 193 } 194 195 static int iqs620_pwm_probe(struct platform_device *pdev) 196 { 197 struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent); 198 struct iqs620_pwm_private *iqs620_pwm; 199 unsigned int val; 200 int ret; 201 202 iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL); 203 if (!iqs620_pwm) 204 return -ENOMEM; 205 206 platform_set_drvdata(pdev, iqs620_pwm); 207 iqs620_pwm->iqs62x = iqs62x; 208 209 ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val); 210 if (ret) 211 return ret; 212 iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT; 213 214 ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val); 215 if (ret) 216 return ret; 217 iqs620_pwm->duty_val = val; 218 219 iqs620_pwm->chip.dev = &pdev->dev; 220 iqs620_pwm->chip.ops = &iqs620_pwm_ops; 221 iqs620_pwm->chip.base = -1; 222 iqs620_pwm->chip.npwm = 1; 223 224 mutex_init(&iqs620_pwm->lock); 225 226 iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier; 227 ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh, 228 &iqs620_pwm->notifier); 229 if (ret) { 230 dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret); 231 return ret; 232 } 233 234 ret = devm_add_action_or_reset(&pdev->dev, 235 iqs620_pwm_notifier_unregister, 236 iqs620_pwm); 237 if (ret) 238 return ret; 239 240 ret = pwmchip_add(&iqs620_pwm->chip); 241 if (ret) 242 dev_err(&pdev->dev, "Failed to add device: %d\n", ret); 243 244 return ret; 245 } 246 247 static int iqs620_pwm_remove(struct platform_device *pdev) 248 { 249 struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev); 250 int ret; 251 252 ret = pwmchip_remove(&iqs620_pwm->chip); 253 if (ret) 254 dev_err(&pdev->dev, "Failed to remove device: %d\n", ret); 255 256 return ret; 257 } 258 259 static struct platform_driver iqs620_pwm_platform_driver = { 260 .driver = { 261 .name = "iqs620a-pwm", 262 }, 263 .probe = iqs620_pwm_probe, 264 .remove = iqs620_pwm_remove, 265 }; 266 module_platform_driver(iqs620_pwm_platform_driver); 267 268 MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>"); 269 MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator"); 270 MODULE_LICENSE("GPL"); 271 MODULE_ALIAS("platform:iqs620a-pwm"); 272