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 device *dev; |
38 | struct notifier_block notifier; |
39 | struct mutex lock; |
40 | unsigned int duty_scale; |
41 | }; |
42 | |
43 | static inline struct iqs620_pwm_private *iqs620_pwm_from_chip(struct pwm_chip *chip) |
44 | { |
45 | return pwmchip_get_drvdata(chip); |
46 | } |
47 | |
48 | static 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(map: iqs62x->regmap, IQS620_PWR_SETTINGS, |
56 | IQS620_PWR_SETTINGS_PWM_OUT); |
57 | |
58 | ret = regmap_write(map: iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, |
59 | val: duty_scale - 1); |
60 | if (ret) |
61 | return ret; |
62 | |
63 | return regmap_set_bits(map: iqs62x->regmap, IQS620_PWR_SETTINGS, |
64 | IQS620_PWR_SETTINGS_PWM_OUT); |
65 | } |
66 | |
67 | static 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(lock: &iqs620_pwm->lock); |
108 | |
109 | return ret; |
110 | } |
111 | |
112 | static 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(lock: &iqs620_pwm->lock); |
132 | |
133 | state->period = IQS620_PWM_PERIOD_NS; |
134 | state->polarity = PWM_POLARITY_NORMAL; |
135 | |
136 | return 0; |
137 | } |
138 | |
139 | static 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, duty_scale: iqs620_pwm->duty_scale); |
159 | |
160 | mutex_unlock(lock: &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 | |
171 | static const struct pwm_ops iqs620_pwm_ops = { |
172 | .apply = iqs620_pwm_apply, |
173 | .get_state = iqs620_pwm_get_state, |
174 | }; |
175 | |
176 | static 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(nh: &iqs620_pwm->iqs62x->nh, |
182 | nb: &iqs620_pwm->notifier); |
183 | if (ret) |
184 | dev_err(iqs620_pwm->dev, |
185 | "Failed to unregister notifier: %d\n" , ret); |
186 | } |
187 | |
188 | static int iqs620_pwm_probe(struct platform_device *pdev) |
189 | { |
190 | struct iqs62x_core *iqs62x = dev_get_drvdata(dev: 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(parent: &pdev->dev, npwm: 1, sizeof_priv: sizeof(*iqs620_pwm)); |
197 | if (IS_ERR(ptr: chip)) |
198 | return PTR_ERR(ptr: 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(map: iqs62x->regmap, IQS620_PWR_SETTINGS, val: &val); |
205 | if (ret) |
206 | return ret; |
207 | |
208 | if (val & IQS620_PWR_SETTINGS_PWM_OUT) { |
209 | ret = regmap_read(map: iqs62x->regmap, IQS620_PWM_DUTY_CYCLE, val: &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(nh: &iqs620_pwm->iqs62x->nh, |
222 | nb: &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 | |
241 | static struct platform_driver iqs620_pwm_platform_driver = { |
242 | .driver = { |
243 | .name = "iqs620a-pwm" , |
244 | }, |
245 | .probe = iqs620_pwm_probe, |
246 | }; |
247 | module_platform_driver(iqs620_pwm_platform_driver); |
248 | |
249 | MODULE_AUTHOR("Jeff LaBundy <jeff@labundy.com>" ); |
250 | MODULE_DESCRIPTION("Azoteq IQS620A PWM Generator" ); |
251 | MODULE_LICENSE("GPL" ); |
252 | MODULE_ALIAS("platform:iqs620a-pwm" ); |
253 | |