1 // SPDX-License-Identifier: GPL-2.0+
3 * Azoteq IQS620A PWM Generator
5 * Copyright (C) 2019 Jeff LaBundy <jeff@labundy.com>
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.
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>
28 #define IQS620_PWR_SETTINGS 0xD2
29 #define IQS620_PWR_SETTINGS_PWM_OUT BIT(7)
31 #define IQS620_PWM_DUTY_CYCLE 0xD8
33 #define IQS620_PWM_PERIOD_NS 1000000
35 struct iqs620_pwm_private {
36 struct iqs62x_core *iqs62x;
38 struct notifier_block notifier;
44 static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
45 const struct pwm_state *state)
47 struct iqs620_pwm_private *iqs620_pwm;
48 struct iqs62x_core *iqs62x;
51 if (state->polarity != PWM_POLARITY_NORMAL)
54 if (state->period < IQS620_PWM_PERIOD_NS)
57 iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
58 iqs62x = iqs620_pwm->iqs62x;
61 * The duty cycle generated by the device is calculated as follows:
63 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms
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.
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.
72 duty_scale = state->duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
74 mutex_lock(&iqs620_pwm->lock);
76 if (!state->enabled || !duty_scale) {
77 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
78 IQS620_PWR_SETTINGS_PWM_OUT, 0);
84 u8 duty_val = min(duty_scale - 1, 0xFF);
86 ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
91 iqs620_pwm->duty_val = duty_val;
94 if (state->enabled && duty_scale) {
95 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
96 IQS620_PWR_SETTINGS_PWM_OUT, 0xFF);
101 iqs620_pwm->out_en = state->enabled;
104 mutex_unlock(&iqs620_pwm->lock);
109 static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
110 struct pwm_state *state)
112 struct iqs620_pwm_private *iqs620_pwm;
114 iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
116 mutex_lock(&iqs620_pwm->lock);
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.
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);
129 mutex_unlock(&iqs620_pwm->lock);
131 state->period = IQS620_PWM_PERIOD_NS;
134 static int iqs620_pwm_notifier(struct notifier_block *notifier,
135 unsigned long event_flags, void *context)
137 struct iqs620_pwm_private *iqs620_pwm;
138 struct iqs62x_core *iqs62x;
141 if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
144 iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
146 iqs62x = iqs620_pwm->iqs62x;
148 mutex_lock(&iqs620_pwm->lock);
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.
155 ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
156 iqs620_pwm->duty_val);
160 ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
161 IQS620_PWR_SETTINGS_PWM_OUT,
162 iqs620_pwm->out_en ? 0xFF : 0);
165 mutex_unlock(&iqs620_pwm->lock);
168 dev_err(iqs620_pwm->chip.dev,
169 "Failed to re-initialize device: %d\n", ret);
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,
182 static void iqs620_pwm_notifier_unregister(void *context)
184 struct iqs620_pwm_private *iqs620_pwm = context;
187 ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
188 &iqs620_pwm->notifier);
190 dev_err(iqs620_pwm->chip.dev,
191 "Failed to unregister notifier: %d\n", ret);
194 static int iqs620_pwm_probe(struct platform_device *pdev)
196 struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
197 struct iqs620_pwm_private *iqs620_pwm;
201 iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL);
205 platform_set_drvdata(pdev, iqs620_pwm);
206 iqs620_pwm->iqs62x = iqs62x;
208 ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
211 iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT;
213 ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
216 iqs620_pwm->duty_val = val;
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;
223 mutex_init(&iqs620_pwm->lock);
225 iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
226 ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
227 &iqs620_pwm->notifier);
229 dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
233 ret = devm_add_action_or_reset(&pdev->dev,
234 iqs620_pwm_notifier_unregister,
239 ret = pwmchip_add(&iqs620_pwm->chip);
241 dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
246 static int iqs620_pwm_remove(struct platform_device *pdev)
248 struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev);
251 ret = pwmchip_remove(&iqs620_pwm->chip);
253 dev_err(&pdev->dev, "Failed to remove device: %d\n", ret);
258 static struct platform_driver iqs620_pwm_platform_driver = {
260 .name = "iqs620a-pwm",
262 .probe = iqs620_pwm_probe,
263 .remove = iqs620_pwm_remove,
265 module_platform_driver(iqs620_pwm_platform_driver);
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");