drivers/pwm/pwm-cros-ec.c

   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  */
  25 struct cros_ec_pwm_device {
  26         struct device *dev;
  27         struct cros_ec_device *ec;
  28         struct pwm_chip chip;
  29 };
  30
  31 static 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
  36 static 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
  59 static 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
  93 static 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
  98 static 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
 117 static 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
 136 static struct pwm_device *
 137 cros_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
 154 static 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
 160 static 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
 188 static 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
 232 static 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
 241 static const struct of_device_id cros_ec_pwm_of_match[] = {
 242         { .compatible = "google,cros-ec-pwm" },
 243         {},
 244 };
 245 MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
 246 #endif
 247
 248 static 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 };
 256 module_platform_driver(cros_ec_pwm_driver);
 257
 258 MODULE_ALIAS("platform:cros-ec-pwm");
 259 MODULE_DESCRIPTION("ChromeOS EC PWM driver");
 260 MODULE_LICENSE("GPL v2");