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