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         u64 duty_scale;
  50         int ret;
  51
  52         if (state->polarity != PWM_POLARITY_NORMAL)
  53                 return -EINVAL;
  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");