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_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
  51                                           IQS620_PWR_SETTINGS_PWM_OUT, 0);
  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 void 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
 131 static int iqs620_pwm_notifier(struct notifier_block *notifier,
 132                                unsigned long event_flags, void *context)
 133 {
 134         struct iqs620_pwm_private *iqs620_pwm;
 135         int ret;
 136
 137         if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
 138                 return NOTIFY_DONE;
 139
 140         iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
 141                                   notifier);
 142
 143         mutex_lock(&iqs620_pwm->lock);
 144
 145         /*
 146          * The parent MFD driver already prints an error message in the event
 147          * of a device reset, so nothing else is printed here unless there is
 148          * an additional failure.
 149          */
 150         ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale);
 151
 152         mutex_unlock(&iqs620_pwm->lock);
 153
 154         if (ret) {
 155                 dev_err(iqs620_pwm->chip.dev,
 156                         "Failed to re-initialize device: %d\n", ret);
 157                 return NOTIFY_BAD;
 158         }
 159
 160         return NOTIFY_OK;
 161 }
 162
 163 static const struct pwm_ops iqs620_pwm_ops = {
 164         .apply = iqs620_pwm_apply,
 165         .get_state = iqs620_pwm_get_state,
 166         .owner = THIS_MODULE,
 167 };
 168
 169 static void iqs620_pwm_notifier_unregister(void *context)
 170 {
 171         struct iqs620_pwm_private *iqs620_pwm = context;
 172         int ret;
 173
 174         ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
 175                                                  &iqs620_pwm->notifier);
 176         if (ret)
 177                 dev_err(iqs620_pwm->chip.dev,
 178                         "Failed to unregister notifier: %d\n", ret);
 179 }
 180
 181 static int iqs620_pwm_probe(struct platform_device *pdev)
 182 {
 183         struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
 184         struct iqs620_pwm_private *iqs620_pwm;
 185         unsigned int val;
 186         int ret;
 187
 188         iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL);
 189         if (!iqs620_pwm)
 190                 return -ENOMEM;
 191
 192         iqs620_pwm->iqs62x = iqs62x;
 193
 194         ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
 195         if (ret)
 196                 return ret;
 197
 198         if (val & IQS620_PWR_SETTINGS_PWM_OUT) {
 199                 ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
 200                 if (ret)
 201                         return ret;
 202
 203                 iqs620_pwm->duty_scale = val + 1;
 204         }
 205
 206         iqs620_pwm->chip.dev = &pdev->dev;
 207         iqs620_pwm->chip.ops = &iqs620_pwm_ops;
 208         iqs620_pwm->chip.npwm = 1;
 209
 210         mutex_init(&iqs620_pwm->lock);
 211
 212         iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
 213         ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
 214                                                &iqs620_pwm->notifier);
 215         if (ret) {
 216                 dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
 217                 return ret;
 218         }
 219
 220         ret = devm_add_action_or_reset(&pdev->dev,
 221                                        iqs620_pwm_notifier_unregister,
 222                                        iqs620_pwm);
 223         if (ret)
 224                 return ret;
 225
 226         ret = devm_pwmchip_add(&pdev->dev, &iqs620_pwm->chip);
 227         if (ret)
 228                 dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
 229
 230         return ret;
 231 }
 232
 233 static struct platform_driver iqs620_pwm_platform_driver = {
 234         .driver = {
 235                 .name = "iqs620a-pwm",
 236         },
 237         .probe = iqs620_pwm_probe,
 238 };
 239 module_platform_driver(iqs620_pwm_platform_driver);
 240
 241 MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>");
 242 MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
 243 MODULE_LICENSE("GPL");
 244 MODULE_ALIAS("platform:iqs620a-pwm");