drivers/pwm/pwm-iqs620a.c

   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");