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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 	bool out_en;
41 	u8 duty_val;
42 };
43 
iqs620_pwm_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)44 static 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 
106 err_mutex:
107 	mutex_unlock(&iqs620_pwm->lock);
108 
109 	return ret;
110 }
111 
iqs620_pwm_get_state(struct pwm_chip * chip,struct pwm_device * pwm,struct pwm_state * state)112 static 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 }
136 
iqs620_pwm_notifier(struct notifier_block * notifier,unsigned long event_flags,void * context)137 static int iqs620_pwm_notifier(struct notifier_block *notifier,
138 			       unsigned long event_flags, void *context)
139 {
140 	struct iqs620_pwm_private *iqs620_pwm;
141 	struct iqs62x_core *iqs62x;
142 	int ret;
143 
144 	if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
145 		return NOTIFY_DONE;
146 
147 	iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
148 				  notifier);
149 	iqs62x = iqs620_pwm->iqs62x;
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 = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
159 			   iqs620_pwm->duty_val);
160 	if (ret)
161 		goto err_mutex;
162 
163 	ret = regmap_update_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
164 				 IQS620_PWR_SETTINGS_PWM_OUT,
165 				 iqs620_pwm->out_en ? 0xff : 0);
166 
167 err_mutex:
168 	mutex_unlock(&iqs620_pwm->lock);
169 
170 	if (ret) {
171 		dev_err(iqs620_pwm->chip.dev,
172 			"Failed to re-initialize device: %d\n", ret);
173 		return NOTIFY_BAD;
174 	}
175 
176 	return NOTIFY_OK;
177 }
178 
179 static const struct pwm_ops iqs620_pwm_ops = {
180 	.apply = iqs620_pwm_apply,
181 	.get_state = iqs620_pwm_get_state,
182 	.owner = THIS_MODULE,
183 };
184 
iqs620_pwm_notifier_unregister(void * context)185 static void iqs620_pwm_notifier_unregister(void *context)
186 {
187 	struct iqs620_pwm_private *iqs620_pwm = context;
188 	int ret;
189 
190 	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
191 						 &iqs620_pwm->notifier);
192 	if (ret)
193 		dev_err(iqs620_pwm->chip.dev,
194 			"Failed to unregister notifier: %d\n", ret);
195 }
196 
iqs620_pwm_probe(struct platform_device * pdev)197 static int iqs620_pwm_probe(struct platform_device *pdev)
198 {
199 	struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
200 	struct iqs620_pwm_private *iqs620_pwm;
201 	unsigned int val;
202 	int ret;
203 
204 	iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL);
205 	if (!iqs620_pwm)
206 		return -ENOMEM;
207 
208 	platform_set_drvdata(pdev, iqs620_pwm);
209 	iqs620_pwm->iqs62x = iqs62x;
210 
211 	ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
212 	if (ret)
213 		return ret;
214 	iqs620_pwm->out_en = val & IQS620_PWR_SETTINGS_PWM_OUT;
215 
216 	ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
217 	if (ret)
218 		return ret;
219 	iqs620_pwm->duty_val = val;
220 
221 	iqs620_pwm->chip.dev = &pdev->dev;
222 	iqs620_pwm->chip.ops = &iqs620_pwm_ops;
223 	iqs620_pwm->chip.base = -1;
224 	iqs620_pwm->chip.npwm = 1;
225 
226 	mutex_init(&iqs620_pwm->lock);
227 
228 	iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
229 	ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
230 					       &iqs620_pwm->notifier);
231 	if (ret) {
232 		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
233 		return ret;
234 	}
235 
236 	ret = devm_add_action_or_reset(&pdev->dev,
237 				       iqs620_pwm_notifier_unregister,
238 				       iqs620_pwm);
239 	if (ret)
240 		return ret;
241 
242 	ret = pwmchip_add(&iqs620_pwm->chip);
243 	if (ret)
244 		dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
245 
246 	return ret;
247 }
248 
iqs620_pwm_remove(struct platform_device * pdev)249 static int iqs620_pwm_remove(struct platform_device *pdev)
250 {
251 	struct iqs620_pwm_private *iqs620_pwm = platform_get_drvdata(pdev);
252 	int ret;
253 
254 	ret = pwmchip_remove(&iqs620_pwm->chip);
255 	if (ret)
256 		dev_err(&pdev->dev, "Failed to remove device: %d\n", ret);
257 
258 	return ret;
259 }
260 
261 static struct platform_driver iqs620_pwm_platform_driver = {
262 	.driver = {
263 		.name = "iqs620a-pwm",
264 	},
265 	.probe = iqs620_pwm_probe,
266 	.remove = iqs620_pwm_remove,
267 };
268 module_platform_driver(iqs620_pwm_platform_driver);
269 
270 MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>");
271 MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
272 MODULE_LICENSE("GPL");
273 MODULE_ALIAS("platform:iqs620a-pwm");
274