aboutsummaryrefslogtreecommitdiff
path: root/drivers/pwm/pwm-iqs620a.c
blob: 7d33e364643601e1ccce4d6f2ba399ce822cc740 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
// SPDX-License-Identifier: GPL-2.0+
/*
 * Azoteq IQS620A PWM Generator
 *
 * Copyright (C) 2019 Jeff LaBundy <jeff@labundy.com>
 *
 * Limitations:
 * - The period is fixed to 1 ms and is generated continuously despite changes
 *   to the duty cycle or enable/disable state.
 * - Changes to the duty cycle or enable/disable state take effect immediately
 *   and may result in a glitch during the period in which the change is made.
 * - The device cannot generate a 0% duty cycle. For duty cycles below 1 / 256
 *   ms, the output is disabled and relies upon an external pull-down resistor
 *   to hold the GPIO3/LTX pin low.
 */

#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/mfd/iqs62x.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/notifier.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/regmap.h>
#include <linux/slab.h>

#define IQS620_PWR_SETTINGS			0xd2
#define IQS620_PWR_SETTINGS_PWM_OUT		BIT(7)

#define IQS620_PWM_DUTY_CYCLE			0xd8

#define IQS620_PWM_PERIOD_NS			1000000

struct iqs620_pwm_private {
	struct iqs62x_core *iqs62x;
	struct pwm_chip chip;
	struct notifier_block notifier;
	struct mutex lock;
	bool out_en;
	u8 duty_val;
};

static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
			    const struct pwm_state *state)
{
	struct iqs620_pwm_private *iqs620_pwm;
	struct iqs62x_core *iqs62x;
	u64 duty_scale;
	int ret;

	if (state->polarity != PWM_POLARITY_NORMAL)
		return -ENOTSUPP;

	if (state->period < IQS620_PWM_PERIOD_NS)
		return -EINVAL;

	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
	iqs62x = iqs620_pwm->iqs62x;

	/*
	 * The duty cycle generated by the device is calculated as follows:
	 *
	 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms
	 *
	 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255
	 * (inclusive). Therefore the lowest duty cycle the device can generate
	 * while the output is enabled is 1 / 256 ms.
	 *
	 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to
	 * allow an external pull-down resistor to hold the GPIO3/LTX pin low.
	 */
	duty_scale = div_u64(state->duty_cycle * 256, IQS620_PWM_PERIOD_NS);

	mutex_lock(&iqs620_pwm->lock);

	if (!state->enabled || !duty_scale) {
		ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
					 IQS620_PWR_SETTINGS_PWM_OUT, 0);
		if (ret)
			goto err_mutex;
	}

	if (duty_scale) {
		u8 duty_val = min_t(u64, duty_scale - 1, 0xff);

		ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
				   duty_val);
		if (ret)
			goto err_mutex;

		iqs620_pwm->duty_val = duty_val;
	}

	if (state->enabled && duty_scale) {
		ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
					 IQS620_PWR_SETTINGS_PWM_OUT, 0xff);
		if (ret)
			goto err_mutex;
	}

	iqs620_pwm->out_en = state->enabled;

err_mutex:
	mutex_unlock(&iqs620_pwm->lock);

	return ret;
}

static void iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
				 struct pwm_state *state)
{
	struct iqs620_pwm_private *iqs620_pwm;

	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);

	mutex_lock(&iqs620_pwm->lock);

	/*
	 * Since the device cannot generate a 0% duty cycle, requests to do so
	 * cause subsequent calls to iqs620_pwm_get_state to report the output
	 * as disabled with duty cycle equal to that which was in use prior to
	 * the request. This is not ideal, but is the best compromise based on
	 * the capabilities of the device.
	 */
	state->enabled = iqs620_pwm->out_en;
	state->duty_cycle = DIV_ROUND_UP((iqs620_pwm->duty_val + 1) *
					 IQS620_PWM_PERIOD_NS, 256);

	mutex_unlock(&iqs620_pwm->lock);

	state->period = IQS620_PWM_PERIOD_NS;
}

static int iqs620_pwm_notifier(struct notifier_block *notifier,
			       unsigned long event_flags, void *context)
{
	struct iqs620_pwm_private *iqs620_pwm;
	struct iqs62x_core *iqs62x;
	int ret;

	if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
		return NOTIFY_DONE;

	iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
				  notifier);
	iqs62x = iqs620_pwm->iqs62x;

	mutex_lock(&iqs620_pwm->lock);

	/*
	 * The parent MFD driver already prints an error message in the event
	 * of a device reset, so nothing else is printed here unless there is
	 * an additional failure.
	 */
	ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
			   iqs620_pwm->duty_val);
	if (ret)
		goto err_mutex;

	ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
				 IQS620_PWR_SETTINGS_PWM_OUT,
				 iqs620_pwm->out_en ? 0xff : 0);

err_mutex:
	mutex_unlock(&iqs620_pwm->lock);

	if (ret) {
		dev_err(iqs620_pwm->chip.dev,
			"Failed to re-initialize device: %d\n", ret);
		return NOTIFY_BAD;
	}

	return NOTIFY_OK;
}

static const struct pwm_ops iqs620_pwm_ops = {
	.apply = iqs620_pwm_apply,
	.get_state = iqs620_pwm_get_state,
	.owner = THIS_MODULE,
};

static void iqs620_pwm_notifier_unregister(void *context)
{
	struct iqs620_pwm_private *iqs620_pwm = context;
	int ret;

	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
						 &iqs620_pwm->notifier);
	if (ret)
		dev_err(iqs620_pwm->chip.dev,
			"Failed to unregister notifier: %d\n", ret);
}

static int iqs620_pwm_probe(struct platform_device *pdev)
{
	struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
	struct iqs620_pwm_private *iqs620_pwm;
	unsigned int val;
	int ret;

	iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL);
	if (!iqs620_pwm)
		return -ENOMEM;

	platform_set_drvdata(pdev, iqs620_pwm);
	iqs620_pwm->iqs62x = iqs62x;

	ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
	if (ret)
		return ret;
	iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT;

	ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
	if (ret)
		return ret;
	iqs620_pwm->duty_val = val;

	iqs620_pwm->chip.dev = &pdev->dev;
	iqs620_pwm->chip.ops = &iqs620_pwm_ops;
	iqs620_pwm->chip.base = -1;
	iqs620_pwm->chip.npwm = 1;

	mutex_init(&iqs620_pwm->lock);

	iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
	ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
					       &iqs620_pwm->notifier);
	if (ret) {
		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
		return ret;
	}

	ret = devm_add_action_or_reset(&pdev->dev,
				       iqs620_pwm_notifier_unregister,
				       iqs620_pwm);
	if (ret)
		return ret;

	ret = pwmchip_add(&iqs620_pwm->chip);
	if (ret)
		dev_err(&pdev->dev, "Failed to add device: %d\n", ret);

	return ret;
}

static int iqs620_pwm_remove(struct platform_device *pdev)
{
	struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev);
	int ret;

	ret = pwmchip_remove(&iqs620_pwm->chip);
	if (ret)
		dev_err(&pdev->dev, "Failed to remove device: %d\n", ret);

	return ret;
}

static struct platform_driver iqs620_pwm_platform_driver = {
	.driver = {
		.name = "iqs620a-pwm",
	},
	.probe = iqs620_pwm_probe,
	.remove = iqs620_pwm_remove,
};
module_platform_driver(iqs620_pwm_platform_driver);

MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>");
MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:iqs620a-pwm");