1/*
  2 * Copyright (C) 2016 Google, Inc
  3 *
  4 * This program is free software; you can redistribute it and/or modify it
  5 * under the terms of the GNU General Public License version 2, as published by
  6 * the Free Software Foundation.
  7 *
  8 * Expose a PWM controlled by the ChromeOS EC to the host processor.
  9 */
 10
 11#include <linux/module.h>
 12#include <linux/mfd/cros_ec.h>
 13#include <linux/mfd/cros_ec_commands.h>
 14#include <linux/platform_device.h>
 15#include <linux/pwm.h>
 16#include <linux/slab.h>
 17
 18/**
 19 * struct cros_ec_pwm_device - Driver data for EC PWM
 20 *
 21 * @dev: Device node
 22 * @ec: Pointer to EC device
 23 * @chip: PWM controller chip
 24 */
 25struct cros_ec_pwm_device {
 26	struct device *dev;
 27	struct cros_ec_device *ec;
 28	struct pwm_chip chip;
 29};
 30
 31static inline struct cros_ec_pwm_device *pwm_to_cros_ec_pwm(struct pwm_chip *c)
 32{
 33	return container_of(c, struct cros_ec_pwm_device, chip);
 34}
 35
 36static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
 37{
 38	struct {
 39		struct cros_ec_command msg;
 40		struct ec_params_pwm_set_duty params;
 41	} __packed buf;
 42	struct ec_params_pwm_set_duty *params = &buf.params;
 43	struct cros_ec_command *msg = &buf.msg;
 44
 45	memset(&buf, 0, sizeof(buf));
 46
 47	msg->version = 0;
 48	msg->command = EC_CMD_PWM_SET_DUTY;
 49	msg->insize = 0;
 50	msg->outsize = sizeof(*params);
 51
 52	params->duty = duty;
 53	params->pwm_type = EC_PWM_TYPE_GENERIC;
 54	params->index = index;
 55
 56	return cros_ec_cmd_xfer_status(ec, msg);
 57}
 58
 59static int __cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index,
 60				  u32 *result)
 61{
 62	struct {
 63		struct cros_ec_command msg;
 64		union {
 65			struct ec_params_pwm_get_duty params;
 66			struct ec_response_pwm_get_duty resp;
 67		};
 68	} __packed buf;
 69	struct ec_params_pwm_get_duty *params = &buf.params;
 70	struct ec_response_pwm_get_duty *resp = &buf.resp;
 71	struct cros_ec_command *msg = &buf.msg;
 72	int ret;
 73
 74	memset(&buf, 0, sizeof(buf));
 75
 76	msg->version = 0;
 77	msg->command = EC_CMD_PWM_GET_DUTY;
 78	msg->insize = sizeof(*resp);
 79	msg->outsize = sizeof(*params);
 80
 81	params->pwm_type = EC_PWM_TYPE_GENERIC;
 82	params->index = index;
 83
 84	ret = cros_ec_cmd_xfer_status(ec, msg);
 85	if (result)
 86		*result = msg->result;
 87	if (ret < 0)
 88		return ret;
 89
 90	return resp->duty;
 91}
 92
 93static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
 94{
 95	return __cros_ec_pwm_get_duty(ec, index, NULL);
 96}
 97
 98static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 99			     struct pwm_state *state)
100{
101	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
102	int duty_cycle;
103
104	/* The EC won't let us change the period */
105	if (state->period != EC_PWM_MAX_DUTY)
106		return -EINVAL;
107
108	/*
109	 * EC doesn't separate the concept of duty cycle and enabled, but
110	 * kernel does. Translate.
111	 */
112	duty_cycle = state->enabled ? state->duty_cycle : 0;
113
114	return cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
115}
116
117static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
118				  struct pwm_state *state)
119{
120	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
121	int ret;
122
123	ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
124	if (ret < 0) {
125		dev_err(chip->dev, "error getting initial duty: %d\n", ret);
126		return;
127	}
128
129	state->enabled = (ret > 0);
130	state->period = EC_PWM_MAX_DUTY;
131
132	/* Note that "disabled" and "duty cycle == 0" are treated the same */
133	state->duty_cycle = ret;
134}
135
136static struct pwm_device *
137cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
138{
139	struct pwm_device *pwm;
140
141	if (args->args[0] >= pc->npwm)
142		return ERR_PTR(-EINVAL);
143
144	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
145	if (IS_ERR(pwm))
146		return pwm;
147
148	/* The EC won't let us change the period */
149	pwm->args.period = EC_PWM_MAX_DUTY;
150
151	return pwm;
152}
153
154static const struct pwm_ops cros_ec_pwm_ops = {
155	.get_state	= cros_ec_pwm_get_state,
156	.apply		= cros_ec_pwm_apply,
157	.owner		= THIS_MODULE,
158};
159
160static int cros_ec_num_pwms(struct cros_ec_device *ec)
161{
162	int i, ret;
163
164	/* The index field is only 8 bits */
165	for (i = 0; i <= U8_MAX; i++) {
166		u32 result = 0;
167
168		ret = __cros_ec_pwm_get_duty(ec, i, &result);
169		/* We want to parse EC protocol errors */
170		if (ret < 0 && !(ret == -EPROTO && result))
171			return ret;
172
173		/*
174		 * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
175		 * responses; everything else is treated as an error.
176		 */
177		if (result == EC_RES_INVALID_COMMAND)
178			return -ENODEV;
179		else if (result == EC_RES_INVALID_PARAM)
180			return i;
181		else if (result)
182			return -EPROTO;
183	}
184
185	return U8_MAX;
186}
187
188static int cros_ec_pwm_probe(struct platform_device *pdev)
189{
190	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
191	struct device *dev = &pdev->dev;
192	struct cros_ec_pwm_device *ec_pwm;
193	struct pwm_chip *chip;
194	int ret;
195
196	if (!ec) {
197		dev_err(dev, "no parent EC device\n");
198		return -EINVAL;
199	}
200
201	ec_pwm = devm_kzalloc(dev, sizeof(*ec_pwm), GFP_KERNEL);
202	if (!ec_pwm)
203		return -ENOMEM;
204	chip = &ec_pwm->chip;
205	ec_pwm->ec = ec;
206
207	/* PWM chip */
208	chip->dev = dev;
209	chip->ops = &cros_ec_pwm_ops;
210	chip->of_xlate = cros_ec_pwm_xlate;
211	chip->of_pwm_n_cells = 1;
212	chip->base = -1;
213	ret = cros_ec_num_pwms(ec);
214	if (ret < 0) {
215		dev_err(dev, "Couldn't find PWMs: %d\n", ret);
216		return ret;
217	}
218	chip->npwm = ret;
219	dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
220
221	ret = pwmchip_add(chip);
222	if (ret < 0) {
223		dev_err(dev, "cannot register PWM: %d\n", ret);
224		return ret;
225	}
226
227	platform_set_drvdata(pdev, ec_pwm);
228
229	return ret;
230}
231
232static int cros_ec_pwm_remove(struct platform_device *dev)
233{
234	struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
235	struct pwm_chip *chip = &ec_pwm->chip;
236
237	return pwmchip_remove(chip);
238}
239
240#ifdef CONFIG_OF
241static const struct of_device_id cros_ec_pwm_of_match[] = {
242	{ .compatible = "google,cros-ec-pwm" },
243	{},
244};
245MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
246#endif
247
248static struct platform_driver cros_ec_pwm_driver = {
249	.probe = cros_ec_pwm_probe,
250	.remove = cros_ec_pwm_remove,
251	.driver = {
252		.name = "cros-ec-pwm",
253		.of_match_table = of_match_ptr(cros_ec_pwm_of_match),
254	},
255};
256module_platform_driver(cros_ec_pwm_driver);
257
258MODULE_ALIAS("platform:cros-ec-pwm");
259MODULE_DESCRIPTION("ChromeOS EC PWM driver");
260MODULE_LICENSE("GPL v2");