Date:   Mon, 11 Apr 2022 17:24:42 +0000
From:   Fabio Baltieri <fabiobaltieri@...omium.org>
To:     Tzung-Bi Shih <tzungbi@...nel.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        chrome-platform@...ts.linux.dev, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH v3 2/4] drivers: pwm: pwm-cros-ec: add channel type
 support

On Mon, Apr 11, 2022 at 03:21:12PM +0000, Fabio Baltieri wrote:
> Add support for EC_PWM_TYPE_DISPLAY_LIGHT and EC_PWM_TYPE_KB_LIGHT pwm
> types to the PWM cros_ec_pwm driver. This allows specifying one of these
> PWM channel by functionality, and let the EC firmware pick the correct
> channel, thus abstracting the hardware implementation from the kernel
> driver.
> 
> To use it, define the node with the "google,cros-ec-pwm-type"
> compatible.
> 
> Signed-off-by: Fabio Baltieri <fabiobaltieri@...omium.org>

Hey Tzung-Bi, ended up not adding your "Reviewed-by" tag since I changed
a chunk of this patch after Rob's comment and there's few options for
handling the DT compatibles, feel free to take another look.

Thanks
Fabio

> ---
>  drivers/pwm/pwm-cros-ec.c | 109 ++++++++++++++++++++++++++++++--------
>  1 file changed, 86 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-cros-ec.c b/drivers/pwm/pwm-cros-ec.c
> index 5e29d9c682c3..83c33958d52b 100644
> --- a/drivers/pwm/pwm-cros-ec.c
> +++ b/drivers/pwm/pwm-cros-ec.c
> @@ -6,23 +6,30 @@
>   */
>  
>  #include <linux/module.h>
> +#include <linux/of_device.h>
>  #include <linux/platform_data/cros_ec_commands.h>
>  #include <linux/platform_data/cros_ec_proto.h>
>  #include <linux/platform_device.h>
>  #include <linux/pwm.h>
>  #include <linux/slab.h>
>  
> +#include <dt-bindings/mfd/cros_ec.h>
> +
> +#define OF_CROS_EC_PWM_TYPE ((void *)1)
> +
>  /**
>   * struct cros_ec_pwm_device - Driver data for EC PWM
>   *
>   * @dev: Device node
>   * @ec: Pointer to EC device
>   * @chip: PWM controller chip
> + * @use_pwm_type: Use PWM types instead of generic channels
>   */
>  struct cros_ec_pwm_device {
>  	struct device *dev;
>  	struct cros_ec_device *ec;
>  	struct pwm_chip chip;
> +	bool use_pwm_type;
>  };
>  
>  /**
> @@ -58,14 +65,31 @@ static void cros_ec_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
>  	kfree(channel);
>  }
>  
> -static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
> +static int cros_ec_dt_type_to_pwm_type(u8 dt_index, u8 *pwm_type)
>  {
> +	switch (dt_index) {
> +	case CROS_EC_PWM_DT_KB_LIGHT:
> +		*pwm_type = EC_PWM_TYPE_KB_LIGHT;
> +		return 0;
> +	case CROS_EC_PWM_DT_DISPLAY_LIGHT:
> +		*pwm_type = EC_PWM_TYPE_DISPLAY_LIGHT;
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int cros_ec_pwm_set_duty(struct cros_ec_pwm_device *ec_pwm, u8 index,
> +				u16 duty)
> +{
> +	struct cros_ec_device *ec = ec_pwm->ec;
>  	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;
> +	int ret;
>  
>  	memset(&buf, 0, sizeof(buf));
>  
> @@ -75,14 +99,25 @@ static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
>  	msg->outsize = sizeof(*params);
>  
>  	params->duty = duty;
> -	params->pwm_type = EC_PWM_TYPE_GENERIC;
> -	params->index = index;
> +
> +	if (ec_pwm->use_pwm_type) {
> +		ret = cros_ec_dt_type_to_pwm_type(index, &params->pwm_type);
> +		if (ret) {
> +			dev_err(ec->dev, "Invalid PWM type index: %d\n", index);
> +			return ret;
> +		}
> +		params->index = 0;
> +	} else {
> +		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)
> +static int cros_ec_pwm_get_duty(struct cros_ec_pwm_device *ec_pwm, u8 index)
>  {
> +	struct cros_ec_device *ec = ec_pwm->ec;
>  	struct {
>  		struct cros_ec_command msg;
>  		union {
> @@ -102,8 +137,17 @@ static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
>  	msg->insize = sizeof(*resp);
>  	msg->outsize = sizeof(*params);
>  
> -	params->pwm_type = EC_PWM_TYPE_GENERIC;
> -	params->index = index;
> +	if (ec_pwm->use_pwm_type) {
> +		ret = cros_ec_dt_type_to_pwm_type(index, &params->pwm_type);
> +		if (ret) {
> +			dev_err(ec->dev, "Invalid PWM type index: %d\n", index);
> +			return ret;
> +		}
> +		params->index = 0;
> +	} else {
> +		params->pwm_type = EC_PWM_TYPE_GENERIC;
> +		params->index = index;
> +	}
>  
>  	ret = cros_ec_cmd_xfer_status(ec, msg);
>  	if (ret < 0)
> @@ -133,7 +177,7 @@ static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  	 */
>  	duty_cycle = state->enabled ? state->duty_cycle : 0;
>  
> -	ret = cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
> +	ret = cros_ec_pwm_set_duty(ec_pwm, pwm->hwpwm, duty_cycle);
>  	if (ret < 0)
>  		return ret;
>  
> @@ -149,7 +193,7 @@ static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>  	struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
>  	int ret;
>  
> -	ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
> +	ret = cros_ec_pwm_get_duty(ec_pwm, pwm->hwpwm);
>  	if (ret < 0) {
>  		dev_err(chip->dev, "error getting initial duty: %d\n", ret);
>  		return;
> @@ -204,13 +248,13 @@ static const struct pwm_ops cros_ec_pwm_ops = {
>   * of PWMs it supports directly, so we have to read the pwm duty cycle for
>   * subsequent channels until we get an error.
>   */
> -static int cros_ec_num_pwms(struct cros_ec_device *ec)
> +static int cros_ec_num_pwms(struct cros_ec_pwm_device *ec_pwm)
>  {
>  	int i, ret;
>  
>  	/* The index field is only 8 bits */
>  	for (i = 0; i <= U8_MAX; i++) {
> -		ret = cros_ec_pwm_get_duty(ec, i);
> +		ret = cros_ec_pwm_get_duty(ec_pwm, i);
>  		/*
>  		 * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
>  		 * responses; everything else is treated as an error.
> @@ -232,10 +276,27 @@ static int cros_ec_num_pwms(struct cros_ec_device *ec)
>  	return U8_MAX;
>  }
>  
> +#ifdef CONFIG_OF
> +static const struct of_device_id cros_ec_pwm_of_match[] = {
> +	{
> +		.compatible = "google,cros-ec-pwm",
> +	},
> +	{
> +		.compatible = "google,cros-ec-pwm-type",
> +		.data = OF_CROS_EC_PWM_TYPE,
> +	},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
> +#else
> +#define cros_ec_pwm_of_match NULL
> +#endif
> +
>  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;
> +	const struct of_device_id *id;
>  	struct cros_ec_pwm_device *ec_pwm;
>  	struct pwm_chip *chip;
>  	int ret;
> @@ -251,17 +312,27 @@ static int cros_ec_pwm_probe(struct platform_device *pdev)
>  	chip = &ec_pwm->chip;
>  	ec_pwm->ec = ec;
>  
> +	id = of_match_device(cros_ec_pwm_of_match, dev);
> +	if (id && id->data == OF_CROS_EC_PWM_TYPE)
> +		ec_pwm->use_pwm_type = true;
> +
>  	/* PWM chip */
>  	chip->dev = dev;
>  	chip->ops = &cros_ec_pwm_ops;
>  	chip->of_xlate = cros_ec_pwm_xlate;
>  	chip->of_pwm_n_cells = 1;
> -	ret = cros_ec_num_pwms(ec);
> -	if (ret < 0) {
> -		dev_err(dev, "Couldn't find PWMs: %d\n", ret);
> -		return ret;
> +
> +	if (ec_pwm->use_pwm_type) {
> +		chip->npwm = CROS_EC_PWM_DT_COUNT;
> +	} else {
> +		ret = cros_ec_num_pwms(ec_pwm);
> +		if (ret < 0) {
> +			dev_err(dev, "Couldn't find PWMs: %d\n", ret);
> +			return ret;
> +		}
> +		chip->npwm = ret;
>  	}
> -	chip->npwm = ret;
> +
>  	dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
>  
>  	ret = pwmchip_add(chip);
> @@ -285,14 +356,6 @@ static int cros_ec_pwm_remove(struct platform_device *dev)
>  	return 0;
>  }
>  
> -#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,
> -- 
> 2.35.1.1178.g4f1659d476-goog
> 

-- 
Fabio Baltieri

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