Re: [PATCH 4/4] pwm: add ChromeOS EC PWM driver

[Gwendal Grignou]

On Fri, May 27, 2016 at 6:39 PM, Brian Norris <briannorris@xxxxxxxxxxxx> wrote:
> Use the new ChromeOS EC EC_CMD_PWM_{GET,SET}_DUTY commands to control
> one or more PWMs attached to the Embedded Controller. Because the EC
> allows us to modify the duty cycle (as a percentage, where U16_MAX is
> 100%) but not the period, we assign the period a fixed value of
> EC_PWM_MAX_DUTY and reject all attempts to change it.
>
> Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
> ---

> + */
> +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_pwm_device *ec_pwm,
> +                                  struct pwm_device *pwm,
> +                                  uint16_t duty)
Given you seprated the pwm stuff from the EC stuff and focusing on
sending a EC command here, the first parameter should be of
cros_ec_device* instead of cros_ec_pwm_device*.
> +{
> +       struct cros_ec_device *ec = ec_pwm->ec;
> +       struct ec_params_pwm_set_duty *params;
> +       struct cros_ec_command *msg;
> +       int ret;
> +
> +       msg = kzalloc(sizeof(*msg) + sizeof(*params), GFP_KERNEL);
Use an ad-hoc data structure on the stack, so you will always be able
to send the command to the EC.
> +       if (!msg)
> +               return -ENOMEM;
> +       params = (void *)&msg->data[0];
> +
> +       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 = pwm->hwpwm;
> +
> +       ret = cros_ec_cmd_xfer_status(ec, msg);
> +       kfree(msg);
> +       return ret;
> +}
> +
> +static int cros_ec_pwm_get_duty(struct cros_ec_pwm_device *ec_pwm,
> +                               struct pwm_device *pwm)
Idem.
> +{
> +       struct cros_ec_device *ec = ec_pwm->ec;
> +       struct ec_params_pwm_get_duty *params;
> +       struct ec_response_pwm_get_duty *resp;
> +       struct cros_ec_command *msg;
> +       int ret;
> +
> +       msg = kzalloc(sizeof(*msg) + max(sizeof(*params), sizeof(*resp)),
Idem.
> +                       GFP_KERNEL);
> +       if (!msg)
> +               return -ENOMEM;
> +       params = (void *)&msg->data[0];
> +       resp = (void *)&msg->data[0];
> +
> +       msg->version = 0;
> +       msg->command = EC_CMD_PWM_GET_DUTY;
> +       msg->insize = sizeof(*params);
> +       msg->outsize = sizeof(*resp);
> +
> +       params->pwm_type = EC_PWM_TYPE_GENERIC;
> +       params->index = pwm->hwpwm;
> +
> +       ret = cros_ec_cmd_xfer_status(ec, msg);
> +       if (ret < 0)
> +               goto out;
> +
> +       ret = resp->duty;
> +
> +out:
> +       kfree(msg);
> +       return ret;
> +}
> +
> +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);
> +
> +       /* The EC won't let us change the period */
> +       if (state->period != EC_PWM_MAX_DUTY)
> +               return -EINVAL;
> +
> +       return cros_ec_pwm_set_duty(ec_pwm, pwm, state->duty_cycle);
I would use ec_pwm->ec here.
> +}
> +
> +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, pwm);
> +       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;
> +       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_pwm_probe(struct platform_device *pdev)
> +{
> +       struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
> +       struct device *dev = &pdev->dev;
> +       struct device_node *np = dev->of_node;
> +       struct cros_ec_pwm_device *ec_pwm;
> +       struct pwm_chip *chip;
> +       u32 val;
> +       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 = of_property_read_u32(np, "google,max-pwms", &val);
> +       if (ret) {
> +               dev_err(dev, "Couldn't read max-pwms property: %d\n", ret);
Does it mean this driver does not work when device tree is not used by
the platform?
The rest of the driver still compiles.
> +               return ret;
> +       }
> +       /* The index field is only 8 bits */
> +       if (val > U8_MAX) {
> +               dev_err(dev, "Can't support %u PWMs\n", val);
> +               return -EINVAL;
> +       }
> +       chip->npwm = val;
> +
> +       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");
> --
> 2.8.0.rc3.226.g39d4020
>