drivers/pwm/pwm-cros-ec.c

   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
  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
  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
  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
  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
  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
 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         /*
 128          * EC doesn't separate the concept of duty cycle and enabled, but
 129          * kernel does. Translate.
 130          */
 131         duty_cycle = state->enabled ? state->duty_cycle : 0;
 132
 133         ret = cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
 134         if (ret < 0)
 135                 return ret;
 136
 137         channel->duty_cycle = state->duty_cycle;
 138
 139         return 0;
 140 }
 141
 142 static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 143                                   struct pwm_state *state)
 144 {
 145         struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
 146         struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
 147         int ret;
 148
 149         ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
 150         if (ret < 0) {
 151                 dev_err(chip->dev, "error getting initial duty: %d\n", ret);
 152                 return;
 153         }
 154
 155         state->enabled = (ret > 0);
 156         state->period = EC_PWM_MAX_DUTY;
 157
 158         /*
 159          * Note that "disabled" and "duty cycle == 0" are treated the same. If
 160          * the cached duty cycle is not zero, used the cached duty cycle. This
 161          * ensures that the configured duty cycle is kept across a disable and
 162          * enable operation and avoids potentially confusing consumers.
 163          *
 164          * For the case of the initial hardware readout, channel->duty_cycle
 165          * will be 0 and the actual duty cycle read from the EC is used.
 166          */
 167         if (ret == 0 && channel->duty_cycle > 0)
 168                 state->duty_cycle = channel->duty_cycle;
 169         else
 170                 state->duty_cycle = ret;
 171 }
 172
 173 static struct pwm_device *
 174 cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
 175 {
 176         struct pwm_device *pwm;
 177
 178         if (args->args[0] >= pc->npwm)
 179                 return ERR_PTR(-EINVAL);
 180
 181         pwm = pwm_request_from_chip(pc, args->args[0], NULL);
 182         if (IS_ERR(pwm))
 183                 return pwm;
 184
 185         /* The EC won't let us change the period */
 186         pwm->args.period = EC_PWM_MAX_DUTY;
 187
 188         return pwm;
 189 }
 190
 191 static const struct pwm_ops cros_ec_pwm_ops = {
 192         .request = cros_ec_pwm_request,
 193         .free = cros_ec_pwm_free,
 194         .get_state      = cros_ec_pwm_get_state,
 195         .apply          = cros_ec_pwm_apply,
 196         .owner          = THIS_MODULE,
 197 };
 198
 199 /*
 200  * Determine the number of supported PWMs. The EC does not return the number
 201  * of PWMs it supports directly, so we have to read the pwm duty cycle for
 202  * subsequent channels until we get an error.
 203  */
 204 static int cros_ec_num_pwms(struct cros_ec_device *ec)
 205 {
 206         int i, ret;
 207
 208         /* The index field is only 8 bits */
 209         for (i = 0; i <= U8_MAX; i++) {
 210                 ret = cros_ec_pwm_get_duty(ec, i);
 211                 /*
 212                  * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
 213                  * responses; everything else is treated as an error.
 214                  * The EC error codes map to -EOPNOTSUPP and -EINVAL,
 215                  * so check for those.
 216                  */
 217                 switch (ret) {
 218                 case -EOPNOTSUPP:       /* invalid command */
 219                         return -ENODEV;
 220                 case -EINVAL:           /* invalid parameter */
 221                         return i;
 222                 default:
 223                         if (ret < 0)
 224                                 return ret;
 225                         break;
 226                 }
 227         }
 228
 229         return U8_MAX;
 230 }
 231
 232 static int cros_ec_pwm_probe(struct platform_device *pdev)
 233 {
 234         struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
 235         struct device *dev = &pdev->dev;
 236         struct cros_ec_pwm_device *ec_pwm;
 237         struct pwm_chip *chip;
 238         int ret;
 239
 240         if (!ec) {
 241                 dev_err(dev, "no parent EC device\n");
 242                 return -EINVAL;
 243         }
 244
 245         ec_pwm = devm_kzalloc(dev, sizeof(*ec_pwm), GFP_KERNEL);
 246         if (!ec_pwm)
 247                 return -ENOMEM;
 248         chip = &ec_pwm->chip;
 249         ec_pwm->ec = ec;
 250
 251         /* PWM chip */
 252         chip->dev = dev;
 253         chip->ops = &cros_ec_pwm_ops;
 254         chip->of_xlate = cros_ec_pwm_xlate;
 255         chip->of_pwm_n_cells = 1;
 256         chip->base = -1;
 257         ret = cros_ec_num_pwms(ec);
 258         if (ret < 0) {
 259                 dev_err(dev, "Couldn't find PWMs: %d\n", ret);
 260                 return ret;
 261         }
 262         chip->npwm = ret;
 263         dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
 264
 265         ret = pwmchip_add(chip);
 266         if (ret < 0) {
 267                 dev_err(dev, "cannot register PWM: %d\n", ret);
 268                 return ret;
 269         }
 270
 271         platform_set_drvdata(pdev, ec_pwm);
 272
 273         return ret;
 274 }
 275
 276 static int cros_ec_pwm_remove(struct platform_device *dev)
 277 {
 278         struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
 279         struct pwm_chip *chip = &ec_pwm->chip;
 280
 281         return pwmchip_remove(chip);
 282 }
 283
 284 #ifdef CONFIG_OF
 285 static const struct of_device_id cros_ec_pwm_of_match[] = {
 286         { .compatible = "google,cros-ec-pwm" },
 287         {},
 288 };
 289 MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
 290 #endif
 291
 292 static struct platform_driver cros_ec_pwm_driver = {
 293         .probe = cros_ec_pwm_probe,
 294         .remove = cros_ec_pwm_remove,
 295         .driver = {
 296                 .name = "cros-ec-pwm",
 297                 .of_match_table = of_match_ptr(cros_ec_pwm_of_match),
 298         },
 299 };
 300 module_platform_driver(cros_ec_pwm_driver);
 301
 302 MODULE_ALIAS("platform:cros-ec-pwm");
 303 MODULE_DESCRIPTION("ChromeOS EC PWM driver");
 304 MODULE_LICENSE("GPL v2");