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
35struct iqs620_pwm_private {
36	struct iqs62x_core *iqs62x;
37	struct device *dev;
38	struct notifier_block notifier;
39	struct mutex lock;
40	unsigned int duty_scale;
41};
42
43static inline struct iqs620_pwm_private *iqs620_pwm_from_chip(struct pwm_chip *chip)
44{
45	return pwmchip_get_drvdata(chip);
46}
47
48static int iqs620_pwm_init(struct iqs620_pwm_private *iqs620_pwm,
49			   unsigned int duty_scale)
50{
51	struct iqs62x_core *iqs62x = iqs620_pwm->iqs62x;
52	int ret;
53
54	if (!duty_scale)
55		return regmap_clear_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
56					 IQS620_PWR_SETTINGS_PWM_OUT);
57
58	ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
59			   duty_scale - 1);
60	if (ret)
61		return ret;
62
63	return regmap_set_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
64			       IQS620_PWR_SETTINGS_PWM_OUT);
65}
66
67static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
68			    const struct pwm_state *state)
69{
70	struct iqs620_pwm_private *iqs620_pwm;
71	unsigned int duty_cycle;
72	unsigned int duty_scale;
73	int ret;
74
75	if (state->polarity != PWM_POLARITY_NORMAL)
76		return -EINVAL;
77
78	if (state->period < IQS620_PWM_PERIOD_NS)
79		return -EINVAL;
80
81	iqs620_pwm = iqs620_pwm_from_chip(chip);
82
83	/*
84	 * The duty cycle generated by the device is calculated as follows:
85	 *
86	 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms
87	 *
88	 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255
89	 * (inclusive). Therefore the lowest duty cycle the device can generate
90	 * while the output is enabled is 1 / 256 ms.
91	 *
92	 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to
93	 * allow an external pull-down resistor to hold the GPIO3/LTX pin low.
94	 */
95	duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS);
96	duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
97
98	if (!state->enabled)
99		duty_scale = 0;
100
101	mutex_lock(&iqs620_pwm->lock);
102
103	ret = iqs620_pwm_init(iqs620_pwm, duty_scale);
104	if (!ret)
105		iqs620_pwm->duty_scale = duty_scale;
106
107	mutex_unlock(&iqs620_pwm->lock);
108
109	return ret;
110}
111
112static int 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 = iqs620_pwm_from_chip(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. This is not ideal, but is the best compromise based on
125	 * the capabilities of the device.
126	 */
127	state->enabled = iqs620_pwm->duty_scale > 0;
128	state->duty_cycle = DIV_ROUND_UP(iqs620_pwm->duty_scale *
129					 IQS620_PWM_PERIOD_NS, 256);
130
131	mutex_unlock(&iqs620_pwm->lock);
132
133	state->period = IQS620_PWM_PERIOD_NS;
134	state->polarity = PWM_POLARITY_NORMAL;
135
136	return 0;
137}
138
139static int iqs620_pwm_notifier(struct notifier_block *notifier,
140			       unsigned long event_flags, void *context)
141{
142	struct iqs620_pwm_private *iqs620_pwm;
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
151	mutex_lock(&iqs620_pwm->lock);
152
153	/*
154	 * The parent MFD driver already prints an error message in the event
155	 * of a device reset, so nothing else is printed here unless there is
156	 * an additional failure.
157	 */
158	ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale);
159
160	mutex_unlock(&iqs620_pwm->lock);
161
162	if (ret) {
163		dev_err(iqs620_pwm->dev,
164			"Failed to re-initialize device: %d\n", ret);
165		return NOTIFY_BAD;
166	}
167
168	return NOTIFY_OK;
169}
170
171static const struct pwm_ops iqs620_pwm_ops = {
172	.apply = iqs620_pwm_apply,
173	.get_state = iqs620_pwm_get_state,
174};
175
176static void iqs620_pwm_notifier_unregister(void *context)
177{
178	struct iqs620_pwm_private *iqs620_pwm = context;
179	int ret;
180
181	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
182						 &iqs620_pwm->notifier);
183	if (ret)
184		dev_err(iqs620_pwm->dev,
185			"Failed to unregister notifier: %d\n", ret);
186}
187
188static int iqs620_pwm_probe(struct platform_device *pdev)
189{
190	struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
191	struct pwm_chip *chip;
192	struct iqs620_pwm_private *iqs620_pwm;
193	unsigned int val;
194	int ret;
195
196	chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*iqs620_pwm));
197	if (IS_ERR(chip))
198		return PTR_ERR(chip);
199
200	iqs620_pwm = iqs620_pwm_from_chip(chip);
201	iqs620_pwm->dev = &pdev->dev;
202	iqs620_pwm->iqs62x = iqs62x;
203
204	ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
205	if (ret)
206		return ret;
207
208	if (val & IQS620_PWR_SETTINGS_PWM_OUT) {
209		ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
210		if (ret)
211			return ret;
212
213		iqs620_pwm->duty_scale = val + 1;
214	}
215
216	chip->ops = &iqs620_pwm_ops;
217
218	mutex_init(&iqs620_pwm->lock);
219
220	iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
221	ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
222					       &iqs620_pwm->notifier);
223	if (ret) {
224		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
225		return ret;
226	}
227
228	ret = devm_add_action_or_reset(&pdev->dev,
229				       iqs620_pwm_notifier_unregister,
230				       iqs620_pwm);
231	if (ret)
232		return ret;
233
234	ret = devm_pwmchip_add(&pdev->dev, chip);
235	if (ret)
236		dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
237
238	return ret;
239}
240
241static struct platform_driver iqs620_pwm_platform_driver = {
242	.driver = {
243		.name = "iqs620a-pwm",
244	},
245	.probe = iqs620_pwm_probe,
246};
247module_platform_driver(iqs620_pwm_platform_driver);
248
249MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>");
250MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
251MODULE_LICENSE("GPL");
252MODULE_ALIAS("platform:iqs620a-pwm");
253