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 pwm_chip chip;
38	struct notifier_block notifier;
39	struct mutex lock;
40	bool out_en;
41	u8 duty_val;
42};
43
44static 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	unsigned int duty_cycle;
50	unsigned int duty_scale;
51	int ret;
52
53	if (state->polarity != PWM_POLARITY_NORMAL)
54		return -ENOTSUPP;
55
56	if (state->period < IQS620_PWM_PERIOD_NS)
57		return -EINVAL;
58
59	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
60	iqs62x = iqs620_pwm->iqs62x;
61
62	/*
63	 * The duty cycle generated by the device is calculated as follows:
64	 *
65	 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms
66	 *
67	 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255
68	 * (inclusive). Therefore the lowest duty cycle the device can generate
69	 * while the output is enabled is 1 / 256 ms.
70	 *
71	 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to
72	 * allow an external pull-down resistor to hold the GPIO3/LTX pin low.
73	 */
74	duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS);
75	duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
76
77	mutex_lock(&iqs620_pwm->lock);
78
79	if (!state->enabled || !duty_scale) {
80		ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
81					 IQS620_PWR_SETTINGS_PWM_OUT, 0);
82		if (ret)
83			goto err_mutex;
84	}
85
86	if (duty_scale) {
87		u8 duty_val = duty_scale - 1;
88
89		ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
90				   duty_val);
91		if (ret)
92			goto err_mutex;
93
94		iqs620_pwm->duty_val = duty_val;
95	}
96
97	if (state->enabled && duty_scale) {
98		ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
99					 IQS620_PWR_SETTINGS_PWM_OUT, 0xff);
100		if (ret)
101			goto err_mutex;
102	}
103
104	iqs620_pwm->out_en = state->enabled;
105
106err_mutex:
107	mutex_unlock(&iqs620_pwm->lock);
108
109	return ret;
110}
111
112static void 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 = container_of(chip, struct iqs620_pwm_private, 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 with duty cycle equal to that which was in use prior to
125	 * the request. This is not ideal, but is the best compromise based on
126	 * the capabilities of the device.
127	 */
128	state->enabled = iqs620_pwm->out_en;
129	state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) *
130					 IQS620_PWM_PERIOD_NS, 256);
131
132	mutex_unlock(&iqs620_pwm->lock);
133
134	state->period = IQS620_PWM_PERIOD_NS;
135	state->polarity = PWM_POLARITY_NORMAL;
136}
137
138static int iqs620_pwm_notifier(struct notifier_block *notifier,
139			       unsigned long event_flags, void *context)
140{
141	struct iqs620_pwm_private *iqs620_pwm;
142	struct iqs62x_core *iqs62x;
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	iqs62x = iqs620_pwm->iqs62x;
151
152	mutex_lock(&iqs620_pwm->lock);
153
154	/*
155	 * The parent MFD driver already prints an error message in the event
156	 * of a device reset, so nothing else is printed here unless there is
157	 * an additional failure.
158	 */
159	ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
160			   iqs620_pwm->duty_val);
161	if (ret)
162		goto err_mutex;
163
164	ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
165				 IQS620_PWR_SETTINGS_PWM_OUT,
166				 iqs620_pwm->out_en ? 0xff : 0);
167
168err_mutex:
169	mutex_unlock(&iqs620_pwm->lock);
170
171	if (ret) {
172		dev_err(iqs620_pwm->chip.dev,
173			"Failed to re-initialize device: %d\n", ret);
174		return NOTIFY_BAD;
175	}
176
177	return NOTIFY_OK;
178}
179
180static const struct pwm_ops iqs620_pwm_ops = {
181	.apply = iqs620_pwm_apply,
182	.get_state = iqs620_pwm_get_state,
183	.owner = THIS_MODULE,
184};
185
186static void iqs620_pwm_notifier_unregister(void *context)
187{
188	struct iqs620_pwm_private *iqs620_pwm = context;
189	int ret;
190
191	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
192						 &iqs620_pwm->notifier);
193	if (ret)
194		dev_err(iqs620_pwm->chip.dev,
195			"Failed to unregister notifier: %d\n", ret);
196}
197
198static int iqs620_pwm_probe(struct platform_device *pdev)
199{
200	struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
201	struct iqs620_pwm_private *iqs620_pwm;
202	unsigned int val;
203	int ret;
204
205	iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL);
206	if (!iqs620_pwm)
207		return -ENOMEM;
208
209	platform_set_drvdata(pdev, iqs620_pwm);
210	iqs620_pwm->iqs62x = iqs62x;
211
212	ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
213	if (ret)
214		return ret;
215	iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT;
216
217	ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
218	if (ret)
219		return ret;
220	iqs620_pwm->duty_val = val;
221
222	iqs620_pwm->chip.dev = &pdev->dev;
223	iqs620_pwm->chip.ops = &iqs620_pwm_ops;
224	iqs620_pwm->chip.base = -1;
225	iqs620_pwm->chip.npwm = 1;
226
227	mutex_init(&iqs620_pwm->lock);
228
229	iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
230	ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
231					       &iqs620_pwm->notifier);
232	if (ret) {
233		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
234		return ret;
235	}
236
237	ret = devm_add_action_or_reset(&pdev->dev,
238				       iqs620_pwm_notifier_unregister,
239				       iqs620_pwm);
240	if (ret)
241		return ret;
242
243	ret = pwmchip_add(&iqs620_pwm->chip);
244	if (ret)
245		dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
246
247	return ret;
248}
249
250static int iqs620_pwm_remove(struct platform_device *pdev)
251{
252	struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev);
253	int ret;
254
255	ret = pwmchip_remove(&iqs620_pwm->chip);
256	if (ret)
257		dev_err(&pdev->dev, "Failed to remove device: %d\n", ret);
258
259	return ret;
260}
261
262static struct platform_driver iqs620_pwm_platform_driver = {
263	.driver = {
264		.name = "iqs620a-pwm",
265	},
266	.probe = iqs620_pwm_probe,
267	.remove = iqs620_pwm_remove,
268};
269module_platform_driver(iqs620_pwm_platform_driver);
270
271MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>");
272MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
273MODULE_LICENSE("GPL");
274MODULE_ALIAS("platform:iqs620a-pwm");
275