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 */
 22struct 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 */
 32struct cros_ec_pwm {
 33	u16 duty_cycle;
 34};
 35
 36static 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
 41static 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
 54static 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
 61static 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
 84static 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
115static 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
145static 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
176static struct pwm_device *
177cros_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
194static 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 */
207static 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
235static 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
278static 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	return pwmchip_remove(chip);
284}
285
286#ifdef CONFIG_OF
287static const struct of_device_id cros_ec_pwm_of_match[] = {
288	{ .compatible = "google,cros-ec-pwm" },
289	{},
290};
291MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
292#endif
293
294static struct platform_driver cros_ec_pwm_driver = {
295	.probe = cros_ec_pwm_probe,
296	.remove = cros_ec_pwm_remove,
297	.driver = {
298		.name = "cros-ec-pwm",
299		.of_match_table = of_match_ptr(cros_ec_pwm_of_match),
300	},
301};
302module_platform_driver(cros_ec_pwm_driver);
303
304MODULE_ALIAS("platform:cros-ec-pwm");
305MODULE_DESCRIPTION("ChromeOS EC PWM driver");
306MODULE_LICENSE("GPL v2");