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 device *dev; 38 struct notifier_block notifier; 39 struct mutex lock; 40 unsigned int duty_scale; 41 }; 42 43 static inline struct iqs620_pwm_private *iqs620_pwm_from_chip(struct pwm_chip *chip) 44 { 45 return pwmchip_get_drvdata(chip); 46 } 47 48 static int iqs620_pwm_init(struct iqs620_pwm_private *iqs620_pwm, 49 unsigned int duty_scale) 50 { 51 struct iqs62x_core *iqs62x = iqs620_pwm->iqs62x; 52 int ret; 53 54 if (!duty_scale) 55 return regmap_clear_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 56 IQS620_PWR_SETTINGS_PWM_OUT); 57 58 ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, 59 duty_scale - 1); 60 if (ret) 61 return ret; 62 63 return regmap_set_bits(iqs62x->regmap, IQS620_PWR_SETTINGS, 64 IQS620_PWR_SETTINGS_PWM_OUT); 65 } 66 67 static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, 68 const struct pwm_state *state) 69 { 70 struct iqs620_pwm_private *iqs620_pwm; 71 unsigned int duty_cycle; 72 unsigned int duty_scale; 73 int ret; 74 75 if (state->polarity != PWM_POLARITY_NORMAL) 76 return -EINVAL; 77 78 if (state->period < IQS620_PWM_PERIOD_NS) 79 return -EINVAL; 80 81 iqs620_pwm = iqs620_pwm_from_chip(chip); 82 83 /* 84 * The duty cycle generated by the device is calculated as follows: 85 * 86 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms 87 * 88 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255 89 * (inclusive). Therefore the lowest duty cycle the device can generate 90 * while the output is enabled is 1 / 256 ms. 91 * 92 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to 93 * allow an external pull-down resistor to hold the GPIO3/LTX pin low. 94 */ 95 duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS); 96 duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS; 97 98 if (!state->enabled) 99 duty_scale = 0; 100 101 mutex_lock(&iqs620_pwm->lock); 102 103 ret = iqs620_pwm_init(iqs620_pwm, duty_scale); 104 if (!ret) 105 iqs620_pwm->duty_scale = duty_scale; 106 107 mutex_unlock(&iqs620_pwm->lock); 108 109 return ret; 110 } 111 112 static int iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, 113 struct pwm_state *state) 114 { 115 struct iqs620_pwm_private *iqs620_pwm; 116 117 iqs620_pwm = iqs620_pwm_from_chip(chip); 118 119 mutex_lock(&iqs620_pwm->lock); 120 121 /* 122 * Since the device cannot generate a 0% duty cycle, requests to do so 123 * cause subsequent calls to iqs620_pwm_get_state to report the output 124 * as disabled. This is not ideal, but is the best compromise based on 125 * the capabilities of the device. 126 */ 127 state->enabled = iqs620_pwm->duty_scale > 0; 128 state->duty_cycle = DIV_ROUND_UP(iqs620_pwm->duty_scale * 129 IQS620_PWM_PERIOD_NS, 256); 130 131 mutex_unlock(&iqs620_pwm->lock); 132 133 state->period = IQS620_PWM_PERIOD_NS; 134 state->polarity = PWM_POLARITY_NORMAL; 135 136 return 0; 137 } 138 139 static int iqs620_pwm_notifier(struct notifier_block *notifier, 140 unsigned long event_flags, void *context) 141 { 142 struct iqs620_pwm_private *iqs620_pwm; 143 int ret; 144 145 if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET))) 146 return NOTIFY_DONE; 147 148 iqs620_pwm = container_of(notifier, struct iqs620_pwm_private, 149 notifier); 150 151 mutex_lock(&iqs620_pwm->lock); 152 153 /* 154 * The parent MFD driver already prints an error message in the event 155 * of a device reset, so nothing else is printed here unless there is 156 * an additional failure. 157 */ 158 ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale); 159 160 mutex_unlock(&iqs620_pwm->lock); 161 162 if (ret) { 163 dev_err(iqs620_pwm->dev, 164 "Failed to re-initialize device: %d\n", ret); 165 return NOTIFY_BAD; 166 } 167 168 return NOTIFY_OK; 169 } 170 171 static const struct pwm_ops iqs620_pwm_ops = { 172 .apply = iqs620_pwm_apply, 173 .get_state = iqs620_pwm_get_state, 174 }; 175 176 static void iqs620_pwm_notifier_unregister(void *context) 177 { 178 struct iqs620_pwm_private *iqs620_pwm = context; 179 int ret; 180 181 ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh, 182 &iqs620_pwm->notifier); 183 if (ret) 184 dev_err(iqs620_pwm->dev, 185 "Failed to unregister notifier: %d\n", ret); 186 } 187 188 static int iqs620_pwm_probe(struct platform_device *pdev) 189 { 190 struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent); 191 struct pwm_chip *chip; 192 struct iqs620_pwm_private *iqs620_pwm; 193 unsigned int val; 194 int ret; 195 196 chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*iqs620_pwm)); 197 if (IS_ERR(chip)) 198 return PTR_ERR(chip); 199 200 iqs620_pwm = iqs620_pwm_from_chip(chip); 201 iqs620_pwm->dev = &pdev->dev; 202 iqs620_pwm->iqs62x = iqs62x; 203 204 ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val); 205 if (ret) 206 return ret; 207 208 if (val & IQS620_PWR_SETTINGS_PWM_OUT) { 209 ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val); 210 if (ret) 211 return ret; 212 213 iqs620_pwm->duty_scale = val + 1; 214 } 215 216 chip->ops = &iqs620_pwm_ops; 217 218 mutex_init(&iqs620_pwm->lock); 219 220 iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier; 221 ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh, 222 &iqs620_pwm->notifier); 223 if (ret) { 224 dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret); 225 return ret; 226 } 227 228 ret = devm_add_action_or_reset(&pdev->dev, 229 iqs620_pwm_notifier_unregister, 230 iqs620_pwm); 231 if (ret) 232 return ret; 233 234 ret = devm_pwmchip_add(&pdev->dev, chip); 235 if (ret) 236 dev_err(&pdev->dev, "Failed to add device: %d\n", ret); 237 238 return ret; 239 } 240 241 static struct platform_driver iqs620_pwm_platform_driver = { 242 .driver = { 243 .name = "iqs620a-pwm", 244 }, 245 .probe = iqs620_pwm_probe, 246 }; 247 module_platform_driver(iqs620_pwm_platform_driver); 248 249 MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>"); 250 MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator"); 251 MODULE_LICENSE("GPL"); 252 MODULE_ALIAS("platform:iqs620a-pwm"); 253