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                                   u32 *result)
  86 {
  87         struct {
  88                 struct cros_ec_command msg;
  89                 union {
  90                         struct ec_params_pwm_get_duty params;
  91                         struct ec_response_pwm_get_duty resp;
  92                 };
  93         } __packed buf;
  94         struct ec_params_pwm_get_duty *params = &buf.params;
  95         struct ec_response_pwm_get_duty *resp = &buf.resp;
  96         struct cros_ec_command *msg = &buf.msg;
  97         int ret;
  98
  99         memset(&buf, 0, sizeof(buf));
 100
 101         msg->version = 0;
 102         msg->command = EC_CMD_PWM_GET_DUTY;
 103         msg->insize = sizeof(*resp);
 104         msg->outsize = sizeof(*params);
 105
 106         params->pwm_type = EC_PWM_TYPE_GENERIC;
 107         params->index = index;
 108
 109         ret = cros_ec_cmd_xfer_status(ec, msg);
 110         if (result)
 111                 *result = msg->result;
 112         if (ret < 0)
 113                 return ret;
 114
 115         return resp->duty;
 116 }
 117
 118 static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
 119 {
 120         return __cros_ec_pwm_get_duty(ec, index, NULL);
 121 }
 122
 123 static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 124                              const struct pwm_state *state)
 125 {
 126         struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
 127         struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
 128         u16 duty_cycle;
 129         int ret;
 130
 131         /* The EC won't let us change the period */
 132         if (state->period != EC_PWM_MAX_DUTY)
 133                 return -EINVAL;
 134
 135         /*
 136          * EC doesn't separate the concept of duty cycle and enabled, but
 137          * kernel does. Translate.
 138          */
 139         duty_cycle = state->enabled ? state->duty_cycle : 0;
 140
 141         ret = cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
 142         if (ret < 0)
 143                 return ret;
 144
 145         channel->duty_cycle = state->duty_cycle;
 146
 147         return 0;
 148 }
 149
 150 static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 151                                   struct pwm_state *state)
 152 {
 153         struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
 154         struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
 155         int ret;
 156
 157         ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
 158         if (ret < 0) {
 159                 dev_err(chip->dev, "error getting initial duty: %d\n", ret);
 160                 return;
 161         }
 162
 163         state->enabled = (ret > 0);
 164         state->period = EC_PWM_MAX_DUTY;
 165
 166         /*
 167          * Note that "disabled" and "duty cycle == 0" are treated the same. If
 168          * the cached duty cycle is not zero, used the cached duty cycle. This
 169          * ensures that the configured duty cycle is kept across a disable and
 170          * enable operation and avoids potentially confusing consumers.
 171          *
 172          * For the case of the initial hardware readout, channel->duty_cycle
 173          * will be 0 and the actual duty cycle read from the EC is used.
 174          */
 175         if (ret == 0 && channel->duty_cycle > 0)
 176                 state->duty_cycle = channel->duty_cycle;
 177         else
 178                 state->duty_cycle = ret;
 179 }
 180
 181 static struct pwm_device *
 182 cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
 183 {
 184         struct pwm_device *pwm;
 185
 186         if (args->args[0] >= pc->npwm)
 187                 return ERR_PTR(-EINVAL);
 188
 189         pwm = pwm_request_from_chip(pc, args->args[0], NULL);
 190         if (IS_ERR(pwm))
 191                 return pwm;
 192
 193         /* The EC won't let us change the period */
 194         pwm->args.period = EC_PWM_MAX_DUTY;
 195
 196         return pwm;
 197 }
 198
 199 static const struct pwm_ops cros_ec_pwm_ops = {
 200         .request = cros_ec_pwm_request,
 201         .free = cros_ec_pwm_free,
 202         .get_state      = cros_ec_pwm_get_state,
 203         .apply          = cros_ec_pwm_apply,
 204         .owner          = THIS_MODULE,
 205 };
 206
 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                 u32 result = 0;
 214
 215                 ret = __cros_ec_pwm_get_duty(ec, i, &result);
 216                 /* We want to parse EC protocol errors */
 217                 if (ret < 0 && !(ret == -EPROTO && result))
 218                         return ret;
 219
 220                 /*
 221                  * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
 222                  * responses; everything else is treated as an error.
 223                  */
 224                 if (result == EC_RES_INVALID_COMMAND)
 225                         return -ENODEV;
 226                 else if (result == EC_RES_INVALID_PARAM)
 227                         return i;
 228                 else if (result)
 229                         return -EPROTO;
 230         }
 231
 232         return U8_MAX;
 233 }
 234
 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         chip->base = -1;
 260         ret = cros_ec_num_pwms(ec);
 261         if (ret < 0) {
 262                 dev_err(dev, "Couldn't find PWMs: %d\n", ret);
 263                 return ret;
 264         }
 265         chip->npwm = ret;
 266         dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
 267
 268         ret = pwmchip_add(chip);
 269         if (ret < 0) {
 270                 dev_err(dev, "cannot register PWM: %d\n", ret);
 271                 return ret;
 272         }
 273
 274         platform_set_drvdata(pdev, ec_pwm);
 275
 276         return ret;
 277 }
 278
 279 static int cros_ec_pwm_remove(struct platform_device *dev)
 280 {
 281         struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
 282         struct pwm_chip *chip = &ec_pwm->chip;
 283
 284         return pwmchip_remove(chip);
 285 }
 286
 287 #ifdef CONFIG_OF
 288 static const struct of_device_id cros_ec_pwm_of_match[] = {
 289         { .compatible = "google,cros-ec-pwm" },
 290         {},
 291 };
 292 MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
 293 #endif
 294
 295 static struct platform_driver cros_ec_pwm_driver = {
 296         .probe = cros_ec_pwm_probe,
 297         .remove = cros_ec_pwm_remove,
 298         .driver = {
 299                 .name = "cros-ec-pwm",
 300                 .of_match_table = of_match_ptr(cros_ec_pwm_of_match),
 301         },
 302 };
 303 module_platform_driver(cros_ec_pwm_driver);
 304
 305 MODULE_ALIAS("platform:cros-ec-pwm");
 306 MODULE_DESCRIPTION("ChromeOS EC PWM driver");
 307 MODULE_LICENSE("GPL v2");