xref: /openbmc/linux/drivers/pwm/pwm-iqs620a.c (revision b20b0971)
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 	unsigned int duty_scale;
41 };
42 
iqs620_pwm_init(struct iqs620_pwm_private * iqs620_pwm,unsigned int duty_scale)43 static int iqs620_pwm_init(struct iqs620_pwm_private *iqs620_pwm,
44 			   unsigned int duty_scale)
45 {
46 	struct iqs62x_core *iqs62x = iqs620_pwm->iqs62x;
47 	int ret;
48 
49 	if (!duty_scale)
50 		return regmap_clear_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
51 					 IQS620_PWR_SETTINGS_PWM_OUT);
52 
53 	ret = regmap_write(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE,
54 			   duty_scale - 1);
55 	if (ret)
56 		return ret;
57 
58 	return regmap_set_bits(iqs62x->regmap, IQS620_PWR_SETTINGS,
59 			       IQS620_PWR_SETTINGS_PWM_OUT);
60 }
61 
iqs620_pwm_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)62 static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
63 			    const struct pwm_state *state)
64 {
65 	struct iqs620_pwm_private *iqs620_pwm;
66 	unsigned int duty_cycle;
67 	unsigned int duty_scale;
68 	int ret;
69 
70 	if (state->polarity != PWM_POLARITY_NORMAL)
71 		return -EINVAL;
72 
73 	if (state->period < IQS620_PWM_PERIOD_NS)
74 		return -EINVAL;
75 
76 	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
77 
78 	/*
79 	 * The duty cycle generated by the device is calculated as follows:
80 	 *
81 	 * duty_cycle = (IQS620_PWM_DUTY_CYCLE + 1) / 256 * 1 ms
82 	 *
83 	 * ...where IQS620_PWM_DUTY_CYCLE is a register value between 0 and 255
84 	 * (inclusive). Therefore the lowest duty cycle the device can generate
85 	 * while the output is enabled is 1 / 256 ms.
86 	 *
87 	 * For lower duty cycles (e.g. 0), the PWM output is simply disabled to
88 	 * allow an external pull-down resistor to hold the GPIO3/LTX pin low.
89 	 */
90 	duty_cycle = min_t(u64, state->duty_cycle, IQS620_PWM_PERIOD_NS);
91 	duty_scale = duty_cycle * 256 / IQS620_PWM_PERIOD_NS;
92 
93 	if (!state->enabled)
94 		duty_scale = 0;
95 
96 	mutex_lock(&iqs620_pwm->lock);
97 
98 	ret = iqs620_pwm_init(iqs620_pwm, duty_scale);
99 	if (!ret)
100 		iqs620_pwm->duty_scale = duty_scale;
101 
102 	mutex_unlock(&iqs620_pwm->lock);
103 
104 	return ret;
105 }
106 
iqs620_pwm_get_state(struct pwm_chip * chip,struct pwm_device * pwm,struct pwm_state * state)107 static int iqs620_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
108 				struct pwm_state *state)
109 {
110 	struct iqs620_pwm_private *iqs620_pwm;
111 
112 	iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip);
113 
114 	mutex_lock(&iqs620_pwm->lock);
115 
116 	/*
117 	 * Since the device cannot generate a 0% duty cycle, requests to do so
118 	 * cause subsequent calls to iqs620_pwm_get_state to report the output
119 	 * as disabled. This is not ideal, but is the best compromise based on
120 	 * the capabilities of the device.
121 	 */
122 	state->enabled = iqs620_pwm->duty_scale > 0;
123 	state->duty_cycle = DIV_ROUND_UP(iqs620_pwm->duty_scale *
124 					 IQS620_PWM_PERIOD_NS, 256);
125 
126 	mutex_unlock(&iqs620_pwm->lock);
127 
128 	state->period = IQS620_PWM_PERIOD_NS;
129 	state->polarity = PWM_POLARITY_NORMAL;
130 
131 	return 0;
132 }
133 
iqs620_pwm_notifier(struct notifier_block * notifier,unsigned long event_flags,void * context)134 static int iqs620_pwm_notifier(struct notifier_block *notifier,
135 			       unsigned long event_flags, void *context)
136 {
137 	struct iqs620_pwm_private *iqs620_pwm;
138 	int ret;
139 
140 	if (!(event_flags & BIT(IQS62X_EVENT_SYS_RESET)))
141 		return NOTIFY_DONE;
142 
143 	iqs620_pwm = container_of(notifier, struct iqs620_pwm_private,
144 				  notifier);
145 
146 	mutex_lock(&iqs620_pwm->lock);
147 
148 	/*
149 	 * The parent MFD driver already prints an error message in the event
150 	 * of a device reset, so nothing else is printed here unless there is
151 	 * an additional failure.
152 	 */
153 	ret = iqs620_pwm_init(iqs620_pwm, iqs620_pwm->duty_scale);
154 
155 	mutex_unlock(&iqs620_pwm->lock);
156 
157 	if (ret) {
158 		dev_err(iqs620_pwm->chip.dev,
159 			"Failed to re-initialize device: %d\n", ret);
160 		return NOTIFY_BAD;
161 	}
162 
163 	return NOTIFY_OK;
164 }
165 
166 static const struct pwm_ops iqs620_pwm_ops = {
167 	.apply = iqs620_pwm_apply,
168 	.get_state = iqs620_pwm_get_state,
169 	.owner = THIS_MODULE,
170 };
171 
iqs620_pwm_notifier_unregister(void * context)172 static void iqs620_pwm_notifier_unregister(void *context)
173 {
174 	struct iqs620_pwm_private *iqs620_pwm = context;
175 	int ret;
176 
177 	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
178 						 &iqs620_pwm->notifier);
179 	if (ret)
180 		dev_err(iqs620_pwm->chip.dev,
181 			"Failed to unregister notifier: %d\n", ret);
182 }
183 
iqs620_pwm_probe(struct platform_device * pdev)184 static int iqs620_pwm_probe(struct platform_device *pdev)
185 {
186 	struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
187 	struct iqs620_pwm_private *iqs620_pwm;
188 	unsigned int val;
189 	int ret;
190 
191 	iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL);
192 	if (!iqs620_pwm)
193 		return -ENOMEM;
194 
195 	iqs620_pwm->iqs62x = iqs62x;
196 
197 	ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);
198 	if (ret)
199 		return ret;
200 
201 	if (val & IQS620_PWR_SETTINGS_PWM_OUT) {
202 		ret = regmap_read(iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, &val);
203 		if (ret)
204 			return ret;
205 
206 		iqs620_pwm->duty_scale = val + 1;
207 	}
208 
209 	iqs620_pwm->chip.dev = &pdev->dev;
210 	iqs620_pwm->chip.ops = &iqs620_pwm_ops;
211 	iqs620_pwm->chip.npwm = 1;
212 
213 	mutex_init(&iqs620_pwm->lock);
214 
215 	iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
216 	ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
217 					       &iqs620_pwm->notifier);
218 	if (ret) {
219 		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
220 		return ret;
221 	}
222 
223 	ret = devm_add_action_or_reset(&pdev->dev,
224 				       iqs620_pwm_notifier_unregister,
225 				       iqs620_pwm);
226 	if (ret)
227 		return ret;
228 
229 	ret = devm_pwmchip_add(&pdev->dev, &iqs620_pwm->chip);
230 	if (ret)
231 		dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
232 
233 	return ret;
234 }
235 
236 static struct platform_driver iqs620_pwm_platform_driver = {
237 	.driver = {
238 		.name = "iqs620a-pwm",
239 	},
240 	.probe = iqs620_pwm_probe,
241 };
242 module_platform_driver(iqs620_pwm_platform_driver);
243 
244 MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>");
245 MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator");
246 MODULE_LICENSE("GPL");
247 MODULE_ALIAS("platform:iqs620a-pwm");
248