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