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         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_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
  59                                   IQS620_PWR_SETTINGS_PWM_OUT, 0xff);
  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");