text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Expose a PWM controlled by the ChromeOS EC to the host processor.
   *
   * Copyright (C) 2016 Google, Inc.
   */
  
  #include <linux/module.h>
  #include <linux/mfd/cros_ec.h>
  #include <linux/mfd/cros_ec_commands.h>
  #include <linux/platform_device.h>
  #include <linux/pwm.h>
  #include <linux/slab.h>
  
  /**
   * struct cros_ec_pwm_device - Driver data for EC PWM
   *
   * @dev: Device node
   * @ec: Pointer to EC device
   * @chip: PWM controller chip
   */
  struct cros_ec_pwm_device {
  	struct device *dev;
  	struct cros_ec_device *ec;
  	struct pwm_chip chip;
  };
  
  static inline struct cros_ec_pwm_device *pwm_to_cros_ec_pwm(struct pwm_chip *c)
  {
  	return container_of(c, struct cros_ec_pwm_device, chip);
  }
  
  static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
  {
  	struct {
  		struct cros_ec_command msg;
  		struct ec_params_pwm_set_duty params;
  	} __packed buf;
  	struct ec_params_pwm_set_duty *params = &buf.params;
  	struct cros_ec_command *msg = &buf.msg;
  
  	memset(&buf, 0, sizeof(buf));
  
  	msg->version = 0;
  	msg->command = EC_CMD_PWM_SET_DUTY;
  	msg->insize = 0;
  	msg->outsize = sizeof(*params);
  
  	params->duty = duty;
  	params->pwm_type = EC_PWM_TYPE_GENERIC;
  	params->index = index;
  
  	return cros_ec_cmd_xfer_status(ec, msg);
  }
  
  static int __cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index,
  				  u32 *result)
  {
  	struct {
  		struct cros_ec_command msg;
  		union {
  			struct ec_params_pwm_get_duty params;
  			struct ec_response_pwm_get_duty resp;
  		};
  	} __packed buf;
  	struct ec_params_pwm_get_duty *params = &buf.params;
  	struct ec_response_pwm_get_duty *resp = &buf.resp;
  	struct cros_ec_command *msg = &buf.msg;
  	int ret;
  
  	memset(&buf, 0, sizeof(buf));
  
  	msg->version = 0;
  	msg->command = EC_CMD_PWM_GET_DUTY;
  	msg->insize = sizeof(*resp);
  	msg->outsize = sizeof(*params);
  
  	params->pwm_type = EC_PWM_TYPE_GENERIC;
  	params->index = index;
  
  	ret = cros_ec_cmd_xfer_status(ec, msg);
  	if (result)
  		*result = msg->result;
  	if (ret < 0)
  		return ret;
  
  	return resp->duty;
  }
  
  static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
  {
  	return __cros_ec_pwm_get_duty(ec, index, NULL);
  }
  
  static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
  			     struct pwm_state *state)
  {
  	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
  	int duty_cycle;
  
  	/* The EC won't let us change the period */
  	if (state->period != EC_PWM_MAX_DUTY)
  		return -EINVAL;
  
  	/*
  	 * EC doesn't separate the concept of duty cycle and enabled, but
  	 * kernel does. Translate.
  	 */
  	duty_cycle = state->enabled ? state->duty_cycle : 0;
  
  	return cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
  }
  
  static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
  				  struct pwm_state *state)
  {
  	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
  	int ret;
  
  	ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
  	if (ret < 0) {
  		dev_err(chip->dev, "error getting initial duty: %d\n", ret);
  		return;
  	}
  
  	state->enabled = (ret > 0);
  	state->period = EC_PWM_MAX_DUTY;
  
  	/* Note that "disabled" and "duty cycle == 0" are treated the same */
  	state->duty_cycle = ret;
  }
  
  static struct pwm_device *
  cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
  {
  	struct pwm_device *pwm;
  
  	if (args->args[0] >= pc->npwm)
  		return ERR_PTR(-EINVAL);
  
  	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
  	if (IS_ERR(pwm))
  		return pwm;
  
  	/* The EC won't let us change the period */
  	pwm->args.period = EC_PWM_MAX_DUTY;
  
  	return pwm;
  }
  
  static const struct pwm_ops cros_ec_pwm_ops = {
  	.get_state	= cros_ec_pwm_get_state,
  	.apply		= cros_ec_pwm_apply,
  	.owner		= THIS_MODULE,
  };
  
  static int cros_ec_num_pwms(struct cros_ec_device *ec)
  {
  	int i, ret;
  
  	/* The index field is only 8 bits */
  	for (i = 0; i <= U8_MAX; i++) {
  		u32 result = 0;
  
  		ret = __cros_ec_pwm_get_duty(ec, i, &result);
  		/* We want to parse EC protocol errors */
  		if (ret < 0 && !(ret == -EPROTO && result))
  			return ret;
  
  		/*
  		 * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
  		 * responses; everything else is treated as an error.
  		 */
  		if (result == EC_RES_INVALID_COMMAND)
  			return -ENODEV;
  		else if (result == EC_RES_INVALID_PARAM)
  			return i;
  		else if (result)
  			return -EPROTO;
  	}
  
  	return U8_MAX;
  }
  
  static int cros_ec_pwm_probe(struct platform_device *pdev)
  {
  	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
  	struct device *dev = &pdev->dev;
  	struct cros_ec_pwm_device *ec_pwm;
  	struct pwm_chip *chip;
  	int ret;
  
  	if (!ec) {
  		dev_err(dev, "no parent EC device\n");
  		return -EINVAL;
  	}
  
  	ec_pwm = devm_kzalloc(dev, sizeof(*ec_pwm), GFP_KERNEL);
  	if (!ec_pwm)
  		return -ENOMEM;
  	chip = &ec_pwm->chip;
  	ec_pwm->ec = ec;
  
  	/* PWM chip */
  	chip->dev = dev;
  	chip->ops = &cros_ec_pwm_ops;
  	chip->of_xlate = cros_ec_pwm_xlate;
  	chip->of_pwm_n_cells = 1;
  	chip->base = -1;
  	ret = cros_ec_num_pwms(ec);
  	if (ret < 0) {
  		dev_err(dev, "Couldn't find PWMs: %d\n", ret);
  		return ret;
  	}
  	chip->npwm = ret;
  	dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
  
  	ret = pwmchip_add(chip);
  	if (ret < 0) {
  		dev_err(dev, "cannot register PWM: %d\n", ret);
  		return ret;
  	}
  
  	platform_set_drvdata(pdev, ec_pwm);
  
  	return ret;
  }
  
  static int cros_ec_pwm_remove(struct platform_device *dev)
  {
  	struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
  	struct pwm_chip *chip = &ec_pwm->chip;
  
  	return pwmchip_remove(chip);
  }
  
  #ifdef CONFIG_OF
  static const struct of_device_id cros_ec_pwm_of_match[] = {
  	{ .compatible = "google,cros-ec-pwm" },
  	{},
  };
  MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
  #endif
  
  static struct platform_driver cros_ec_pwm_driver = {
  	.probe = cros_ec_pwm_probe,
  	.remove = cros_ec_pwm_remove,
  	.driver = {
  		.name = "cros-ec-pwm",
  		.of_match_table = of_match_ptr(cros_ec_pwm_of_match),
  	},
  };
  module_platform_driver(cros_ec_pwm_driver);
  
  MODULE_ALIAS("platform:cros-ec-pwm");
  MODULE_DESCRIPTION("ChromeOS EC PWM driver");
  MODULE_LICENSE("GPL v2");
  