1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Expose a PWM controlled by the ChromeOS EC to the host processor.
4  *
5  * Copyright (C) 2016 Google, Inc.
6  */
7 
8 #include <linux/module.h>
9 #include <linux/platform_data/cros_ec_commands.h>
10 #include <linux/platform_data/cros_ec_proto.h>
11 #include <linux/platform_device.h>
12 #include <linux/pwm.h>
13 #include <linux/slab.h>
14 
15 /**
16  * struct cros_ec_pwm_device - Driver data for EC PWM
17  *
18  * @dev: Device node
19  * @ec: Pointer to EC device
20  * @chip: PWM controller chip
21  */
22 struct cros_ec_pwm_device {
23 	struct device *dev;
24 	struct cros_ec_device *ec;
25 	struct pwm_chip chip;
26 };
27 
28 /**
29  * struct cros_ec_pwm - per-PWM driver data
30  * @duty_cycle: cached duty cycle
31  */
32 struct cros_ec_pwm {
33 	u16 duty_cycle;
34 };
35 
pwm_to_cros_ec_pwm(struct pwm_chip * c)36 static inline struct cros_ec_pwm_device *pwm_to_cros_ec_pwm(struct pwm_chip *c)
37 {
38 	return container_of(c, struct cros_ec_pwm_device, chip);
39 }
40 
cros_ec_pwm_request(struct pwm_chip * chip,struct pwm_device * pwm)41 static int cros_ec_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
42 {
43 	struct cros_ec_pwm *channel;
44 
45 	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
46 	if (!channel)
47 		return -ENOMEM;
48 
49 	pwm_set_chip_data(pwm, channel);
50 
51 	return 0;
52 }
53 
cros_ec_pwm_free(struct pwm_chip * chip,struct pwm_device * pwm)54 static void cros_ec_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
55 {
56 	struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
57 
58 	kfree(channel);
59 }
60 
cros_ec_pwm_set_duty(struct cros_ec_device * ec,u8 index,u16 duty)61 static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
62 {
63 	struct {
64 		struct cros_ec_command msg;
65 		struct ec_params_pwm_set_duty params;
66 	} __packed buf;
67 	struct ec_params_pwm_set_duty *params = &buf.params;
68 	struct cros_ec_command *msg = &buf.msg;
69 
70 	memset(&buf, 0, sizeof(buf));
71 
72 	msg->version = 0;
73 	msg->command = EC_CMD_PWM_SET_DUTY;
74 	msg->insize = 0;
75 	msg->outsize = sizeof(*params);
76 
77 	params->duty = duty;
78 	params->pwm_type = EC_PWM_TYPE_GENERIC;
79 	params->index = index;
80 
81 	return cros_ec_cmd_xfer_status(ec, msg);
82 }
83 
cros_ec_pwm_get_duty(struct cros_ec_device * ec,u8 index)84 static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
85 {
86 	struct {
87 		struct cros_ec_command msg;
88 		union {
89 			struct ec_params_pwm_get_duty params;
90 			struct ec_response_pwm_get_duty resp;
91 		};
92 	} __packed buf;
93 	struct ec_params_pwm_get_duty *params = &buf.params;
94 	struct ec_response_pwm_get_duty *resp = &buf.resp;
95 	struct cros_ec_command *msg = &buf.msg;
96 	int ret;
97 
98 	memset(&buf, 0, sizeof(buf));
99 
100 	msg->version = 0;
101 	msg->command = EC_CMD_PWM_GET_DUTY;
102 	msg->insize = sizeof(*resp);
103 	msg->outsize = sizeof(*params);
104 
105 	params->pwm_type = EC_PWM_TYPE_GENERIC;
106 	params->index = index;
107 
108 	ret = cros_ec_cmd_xfer_status(ec, msg);
109 	if (ret < 0)
110 		return ret;
111 
112 	return resp->duty;
113 }
114 
cros_ec_pwm_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)115 static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
116 			     const struct pwm_state *state)
117 {
118 	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
119 	struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
120 	u16 duty_cycle;
121 	int ret;
122 
123 	/* The EC won't let us change the period */
124 	if (state->period != EC_PWM_MAX_DUTY)
125 		return -EINVAL;
126 
127 	if (state->polarity != PWM_POLARITY_NORMAL)
128 		return -EINVAL;
129 
130 	/*
131 	 * EC doesn't separate the concept of duty cycle and enabled, but
132 	 * kernel does. Translate.
133 	 */
134 	duty_cycle = state->enabled ? state->duty_cycle : 0;
135 
136 	ret = cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
137 	if (ret < 0)
138 		return ret;
139 
140 	channel->duty_cycle = state->duty_cycle;
141 
142 	return 0;
143 }
144 
cros_ec_pwm_get_state(struct pwm_chip * chip,struct pwm_device * pwm,struct pwm_state * state)145 static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
146 				  struct pwm_state *state)
147 {
148 	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
149 	struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
150 	int ret;
151 
152 	ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
153 	if (ret < 0) {
154 		dev_err(chip->dev, "error getting initial duty: %d\n", ret);
155 		return;
156 	}
157 
158 	state->enabled = (ret > 0);
159 	state->period = EC_PWM_MAX_DUTY;
160 
161 	/*
162 	 * Note that "disabled" and "duty cycle == 0" are treated the same. If
163 	 * the cached duty cycle is not zero, used the cached duty cycle. This
164 	 * ensures that the configured duty cycle is kept across a disable and
165 	 * enable operation and avoids potentially confusing consumers.
166 	 *
167 	 * For the case of the initial hardware readout, channel->duty_cycle
168 	 * will be 0 and the actual duty cycle read from the EC is used.
169 	 */
170 	if (ret == 0 && channel->duty_cycle > 0)
171 		state->duty_cycle = channel->duty_cycle;
172 	else
173 		state->duty_cycle = ret;
174 }
175 
176 static struct pwm_device *
cros_ec_pwm_xlate(struct pwm_chip * pc,const struct of_phandle_args * args)177 cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
178 {
179 	struct pwm_device *pwm;
180 
181 	if (args->args[0] >= pc->npwm)
182 		return ERR_PTR(-EINVAL);
183 
184 	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
185 	if (IS_ERR(pwm))
186 		return pwm;
187 
188 	/* The EC won't let us change the period */
189 	pwm->args.period = EC_PWM_MAX_DUTY;
190 
191 	return pwm;
192 }
193 
194 static const struct pwm_ops cros_ec_pwm_ops = {
195 	.request = cros_ec_pwm_request,
196 	.free = cros_ec_pwm_free,
197 	.get_state	= cros_ec_pwm_get_state,
198 	.apply		= cros_ec_pwm_apply,
199 	.owner		= THIS_MODULE,
200 };
201 
202 /*
203  * Determine the number of supported PWMs. The EC does not return the number
204  * of PWMs it supports directly, so we have to read the pwm duty cycle for
205  * subsequent channels until we get an error.
206  */
cros_ec_num_pwms(struct cros_ec_device * ec)207 static int cros_ec_num_pwms(struct cros_ec_device *ec)
208 {
209 	int i, ret;
210 
211 	/* The index field is only 8 bits */
212 	for (i = 0; i <= U8_MAX; i++) {
213 		ret = cros_ec_pwm_get_duty(ec, i);
214 		/*
215 		 * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
216 		 * responses; everything else is treated as an error.
217 		 * The EC error codes map to -EOPNOTSUPP and -EINVAL,
218 		 * so check for those.
219 		 */
220 		switch (ret) {
221 		case -EOPNOTSUPP:	/* invalid command */
222 			return -ENODEV;
223 		case -EINVAL:		/* invalid parameter */
224 			return i;
225 		default:
226 			if (ret < 0)
227 				return ret;
228 			break;
229 		}
230 	}
231 
232 	return U8_MAX;
233 }
234 
cros_ec_pwm_probe(struct platform_device * pdev)235 static int cros_ec_pwm_probe(struct platform_device *pdev)
236 {
237 	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
238 	struct device *dev = &pdev->dev;
239 	struct cros_ec_pwm_device *ec_pwm;
240 	struct pwm_chip *chip;
241 	int ret;
242 
243 	if (!ec) {
244 		dev_err(dev, "no parent EC device\n");
245 		return -EINVAL;
246 	}
247 
248 	ec_pwm = devm_kzalloc(dev, sizeof(*ec_pwm), GFP_KERNEL);
249 	if (!ec_pwm)
250 		return -ENOMEM;
251 	chip = &ec_pwm->chip;
252 	ec_pwm->ec = ec;
253 
254 	/* PWM chip */
255 	chip->dev = dev;
256 	chip->ops = &cros_ec_pwm_ops;
257 	chip->of_xlate = cros_ec_pwm_xlate;
258 	chip->of_pwm_n_cells = 1;
259 	ret = cros_ec_num_pwms(ec);
260 	if (ret < 0) {
261 		dev_err(dev, "Couldn't find PWMs: %d\n", ret);
262 		return ret;
263 	}
264 	chip->npwm = ret;
265 	dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
266 
267 	ret = pwmchip_add(chip);
268 	if (ret < 0) {
269 		dev_err(dev, "cannot register PWM: %d\n", ret);
270 		return ret;
271 	}
272 
273 	platform_set_drvdata(pdev, ec_pwm);
274 
275 	return ret;
276 }
277 
cros_ec_pwm_remove(struct platform_device * dev)278 static int cros_ec_pwm_remove(struct platform_device *dev)
279 {
280 	struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
281 	struct pwm_chip *chip = &ec_pwm->chip;
282 
283 	pwmchip_remove(chip);
284 
285 	return 0;
286 }
287 
288 #ifdef CONFIG_OF
289 static const struct of_device_id cros_ec_pwm_of_match[] = {
290 	{ .compatible = "google,cros-ec-pwm" },
291 	{},
292 };
293 MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
294 #endif
295 
296 static struct platform_driver cros_ec_pwm_driver = {
297 	.probe = cros_ec_pwm_probe,
298 	.remove = cros_ec_pwm_remove,
299 	.driver = {
300 		.name = "cros-ec-pwm",
301 		.of_match_table = of_match_ptr(cros_ec_pwm_of_match),
302 	},
303 };
304 module_platform_driver(cros_ec_pwm_driver);
305 
306 MODULE_ALIAS("platform:cros-ec-pwm");
307 MODULE_DESCRIPTION("ChromeOS EC PWM driver");
308 MODULE_LICENSE("GPL v2");
309