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