Date:   Wed, 12 Oct 2022 14:38:13 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Naresh Solanki <naresh.solanki@...ements.com>,
        devicetree@...r.kernel.org, Jean Delvare <jdelvare@...e.com>
Cc:     linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>
Subject: Re: [PATCH v3 3/3] hwmon: (max6639) Change from pdata to dt
 configuration

On 10/12/22 13:57, Naresh Solanki wrote:
> max6639_platform_data is not used by any in-kernel driver and does not
> address the MAX6639 fans separately.
> Move to device tree configuration with explicit properties to configure
> each fan.
> 
> Non-DT platform can still use this module with its default
> configuration.
> 
> Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
> ---
>   drivers/hwmon/max6639.c | 205 +++++++++++++++++++++++++++++-----------
>   1 file changed, 152 insertions(+), 53 deletions(-)
> 
> diff --git a/drivers/hwmon/max6639.c b/drivers/hwmon/max6639.c
> index 9b895402c80d..2fc096a00e21 100644
> --- a/drivers/hwmon/max6639.c
> +++ b/drivers/hwmon/max6639.c
> @@ -19,7 +19,6 @@
>   #include <linux/hwmon-sysfs.h>
>   #include <linux/err.h>
>   #include <linux/mutex.h>
> -#include <linux/platform_data/max6639.h>
>   
>   /* Addresses to scan */
>   static const unsigned short normal_i2c[] = { 0x2c, 0x2e, 0x2f, I2C_CLIENT_END };
> @@ -85,9 +84,9 @@ struct max6639_data {
>   	u8 temp_ot[2];		/* OT Temperature, 0..255 C (->_emergency) */
>   
>   	/* Register values initialized only once */
> -	u8 ppr;			/* Pulses per rotation 0..3 for 1..4 ppr */
> -	u8 rpm_range;		/* Index in above rpm_ranges table */
> -
> +	u8 ppr[2];		/* Pulses per rotation 0..3 for 1..4 ppr */
> +	u8 rpm_range[2];	/* Index in above rpm_ranges table */
> +	u8 pwm_polarity[2];	/* Fans PWM polarity, 0..1 */
>   	/* Optional regulator for FAN supply */
>   	struct regulator *reg;
>   };
> @@ -319,7 +318,7 @@ static ssize_t fan_input_show(struct device *dev,
>   		return PTR_ERR(data);
>   
>   	return sprintf(buf, "%d\n", FAN_FROM_REG(data->fan[attr->index],
> -		       data->rpm_range));
> +		       data->rpm_range[attr->index]));
>   }
>   
>   static ssize_t alarm_show(struct device *dev,
> @@ -386,29 +385,39 @@ static struct attribute *max6639_attrs[] = {
>   ATTRIBUTE_GROUPS(max6639);
>   
>   /*
> - *  returns respective index in rpm_ranges table
> - *  1 by default on invalid range
> + *  Get respective index in rpm_ranges table
>    */
> -static int rpm_range_to_reg(int range)
> +static int rpm_range_to_index(struct device *dev, u8 *index, int rpm)
>   {
> -	int i;
> -
> -	for (i = 0; i < ARRAY_SIZE(rpm_ranges); i++) {
> -		if (rpm_ranges[i] == range)
> -			return i;
> +	if (rpm < 0)
> +		return -EINVAL;
> +
> +	/* Set index based on chip support */
> +	switch (rpm) {
> +	case 0 ... 2000:
> +		*index = 0;
> +		break;
> +	case 2001 ... 4000:
> +		*index = 1;
> +		break;
> +	case 4001 ... 8000:
> +		*index = 2;
> +		break;
> +	case 8001 ... 16000:
> +		*index = 3;
> +		break;
> +	default:
> +		/* Use max range for higher RPM */
> +		dev_warn(dev, "RPM higher than supported range.");

It is illogical to complain about that but not about other invalid values.

> +		*index = 3;
>   	}
> -
> -	return 1; /* default: 4000 RPM */
> +	return 0;

The return value can be used both as error indicator (return value < 0)
and index (return value >= 0). It is not necessary to introduce a pointer.

>   }
>   
>   static int max6639_init_client(struct i2c_client *client,
>   			       struct max6639_data *data)
>   {
> -	struct max6639_platform_data *max6639_info =
> -		dev_get_platdata(&client->dev);
> -	int i;
> -	int rpm_range = 1; /* default: 4000 RPM */
> -	int err;
> +	int i, err;
>   
>   	/* Reset chip to default values, see below for GCONFIG setup */
>   	err = i2c_smbus_write_byte_data(client, MAX6639_REG_GCONFIG,
> @@ -416,51 +425,32 @@ static int max6639_init_client(struct i2c_client *client,
>   	if (err)
>   		goto exit;
>   
> -	/* Fans pulse per revolution is 2 by default */
> -	if (max6639_info && max6639_info->ppr > 0 &&
> -			max6639_info->ppr < 5)
> -		data->ppr = max6639_info->ppr;
> -	else
> -		data->ppr = 2;
> -	data->ppr -= 1;
> -
> -	if (max6639_info)
> -		rpm_range = rpm_range_to_reg(max6639_info->rpm_range);
> -	data->rpm_range = rpm_range;
> -
>   	for (i = 0; i < 2; i++) {
>   
>   		/* Set Fan pulse per revolution */
>   		err = i2c_smbus_write_byte_data(client,
>   				MAX6639_REG_FAN_PPR(i),
> -				data->ppr << 6);
> +				data->ppr[i] << 6);
>   		if (err)
>   			goto exit;
>   
>   		/* Fans config PWM, RPM */
>   		err = i2c_smbus_write_byte_data(client,
>   			MAX6639_REG_FAN_CONFIG1(i),
> -			MAX6639_FAN_CONFIG1_PWM | rpm_range);
> +			MAX6639_FAN_CONFIG1_PWM | data->rpm_range[i]);
>   		if (err)
>   			goto exit;
>   
> -		/* Fans PWM polarity high by default */
> -		if (max6639_info && max6639_info->pwm_polarity == 0)
> -			err = i2c_smbus_write_byte_data(client,
> -				MAX6639_REG_FAN_CONFIG2a(i), 0x00);
> -		else
> -			err = i2c_smbus_write_byte_data(client,
> -				MAX6639_REG_FAN_CONFIG2a(i), 0x02);
> -		if (err)
> -			goto exit;
> +		/* Fans PWM polarity */
> +		err = i2c_smbus_write_byte_data(client,
> +			MAX6639_REG_FAN_CONFIG2a(i), data->pwm_polarity[i] ? 0x02 : 0x00);
>   
>   		/*
> -		 * /THERM full speed enable,
> +		 * /THERM full speed disable,
>   		 * PWM frequency 25kHz, see also GCONFIG below
>   		 */
>   		err = i2c_smbus_write_byte_data(client,
> -			MAX6639_REG_FAN_CONFIG3(i),
> -			MAX6639_FAN_CONFIG3_THERM_FULL_SPEED | 0x03);
> +			MAX6639_REG_FAN_CONFIG3(i), 0x03);
>   		if (err)
>   			goto exit;
>   
> @@ -483,8 +473,6 @@ static int max6639_init_client(struct i2c_client *client,
>   		if (err)
>   			goto exit;
>   
> -		/* PWM 120/120 (i.e. 100%) */
> -		data->pwm[i] = 120;
>   		err = i2c_smbus_write_byte_data(client,
>   				MAX6639_REG_TARGTDUTY(i), data->pwm[i]);
>   		if (err)
> @@ -524,12 +512,92 @@ static void max6639_regulator_disable(void *data)
>   	regulator_disable(data);
>   }
>   
> +static int max6639_probe_child_from_dt(struct i2c_client *client,
> +				      struct device_node *child,
> +				      struct max6639_data *data)
> +
> +{
> +	struct device *dev = &client->dev;
> +	u32 i, val, maxrpm;
> +	int err;
> +
> +	err = of_property_read_u32(child, "reg", &i);
> +	if (err) {
> +		dev_err(dev, "missing reg property of %pOFn\n", child);
> +		return err;
> +	}
> +
> +	if (i >= 2) {
> +		dev_err(dev, "invalid reg %d of %pOFn\n", i, child);
> +		return -EINVAL;
> +	}
> +
> +	err = of_property_read_u32(child, "pulses-per-revolution", &val);
> +	if (err) {
> +		dev_err(dev, "missing pulses-per-revolution property of %pOFn\n", child);
> +		return err;
> +	}
> +
> +	if (val < 0 || val > 5) {
> +		dev_err(dev, "invalid pulses-per-revolution %d of %pOFn\n", val, child);
> +		return -EINVAL;
> +	}
> +	data->ppr[i] = val;
> +
> +	err = of_property_read_u32(child, "max-rpm", &maxrpm);
> +	if (err) {
> +		dev_err(dev, "missing max-rpm property of %pOFn\n", child);
> +		return err;
> +	}
> +
> +	err = rpm_range_to_index(dev, &data->rpm_range[i], maxrpm);
> +	if (err) {
> +		dev_err(dev, "invalid max-rpm %d of %pOFn\n", maxrpm, child);
> +		return err;
> +	}
> +
> +
Dual empty line.

> +	err = of_property_read_u32(child, "target-rpm", &val);
> +	/* Convert to PWM from provided target RPM */
> +	if (!err && val != 0)
> +		data->pwm[i] =
> +			(u8)(val * 120 / maxrpm);
> +

It is not acceptable for any of those missing properties to result
in errors. Use current chip values as default if values are not
provided.

> +	data->pwm_polarity[i] =  of_property_read_bool(child, "pwm-polarity-inverse");
> +
> +	return 0;
> +}
> +static int max6639_probe_from_dt(struct i2c_client *client, struct max6639_data *data)
> +{
> +	struct device *dev = &client->dev;
> +	const struct device_node *np = dev->of_node;
> +	struct device_node *child;
> +	int err;
> +
> +	/* Compatible with non-DT platforms */
> +	if (!np)
> +		return 0;
> +
> +	for_each_child_of_node(np, child) {
> +		if (strcmp(child->name, "fan"))
> +			continue;
> +
> +		err = max6639_probe_child_from_dt(client, child, data);
> +		if (err) {
> +			of_node_put(child);
> +			return err;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>   static int max6639_probe(struct i2c_client *client)
>   {
>   	struct device *dev = &client->dev;
>   	struct max6639_data *data;
>   	struct device *hwmon_dev;
> -	int err;
> +	int err, i;
>   
>   	data = devm_kzalloc(dev, sizeof(struct max6639_data), GFP_KERNEL);
>   	if (!data)
> @@ -539,9 +607,11 @@ static int max6639_probe(struct i2c_client *client)
>   
>   	data->reg = devm_regulator_get_optional(dev, "fan");
>   	if (IS_ERR(data->reg)) {
> -		if (PTR_ERR(data->reg) != -ENODEV)
> -			return PTR_ERR(data->reg);
> -
> +		if (PTR_ERR(data->reg) != -ENODEV) {
> +			err = (int)PTR_ERR(data->reg);
> +			dev_warn(dev, "Failed looking up fan supply: %d\n", err);

This is an unrelated change. It is not common to issue a warning
in that situation, and I am not inclined to accept it. Besides,
the function can return -EPROBE_DEFER, and any messages associated
with that are unacceptable.

> +			return err;
> +		}
>   		data->reg = NULL;
>   	} else {
>   		/* Spin up fans */
> @@ -560,6 +630,24 @@ static int max6639_probe(struct i2c_client *client)
>   
>   	mutex_init(&data->update_lock);
>   
> +	/* default values */
> +	for (i = 0; i < 2; i++) {
> +		/* 4000 RPM */
> +		data->rpm_range[i] = 1;
> +		data->ppr[i] = 2;
> +		data->pwm_polarity[i] = 1;
> +		/* Max. temp. 80C/90C/100C */
> +		data->temp_therm[i] = 80;
> +		data->temp_alert[i] = 90;
> +		data->temp_ot[i] = 100;
> +		/* PWM 120/120 (i.e. 100%) */
> +		data->pwm[i] = 120;
> +	}

As I said, defaults are values currently programmed into the chip,
not some random values.

> +
> +	err = max6639_probe_from_dt(client, data);
> +	if (err)
> +		return err;
> +
>   	/* Initialize the max6639 chip */
>   	err = max6639_init_client(client, data);
>   	if (err < 0)
> @@ -571,6 +659,7 @@ static int max6639_probe(struct i2c_client *client)
>   	return PTR_ERR_OR_ZERO(hwmon_dev);
>   }
>   
> +#if IS_ENABLED(CONFIG_PM_SLEEP)
>   static int max6639_suspend(struct device *dev)
>   {
>   	struct i2c_client *client = to_i2c_client(dev);
> @@ -608,6 +697,7 @@ static int max6639_resume(struct device *dev)
>   	return i2c_smbus_write_byte_data(client,
>   			MAX6639_REG_GCONFIG, ret & ~MAX6639_GCONFIG_STANDBY);
>   }
> +#endif

This can be done without #ifdef.
>   
>   static const struct i2c_device_id max6639_id[] = {
>   	{"max6639", 0},
> @@ -616,13 +706,22 @@ static const struct i2c_device_id max6639_id[] = {
>   
>   MODULE_DEVICE_TABLE(i2c, max6639_id);
>   
> -static DEFINE_SIMPLE_DEV_PM_OPS(max6639_pm_ops, max6639_suspend, max6639_resume);
> +#ifdef CONFIG_OF
> +static const struct of_device_id maxim_of_platform_match[] = {
> +	{.compatible = "maxim,max6639"},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, maxim_of_platform_match);
> +#endif
> +
> +static SIMPLE_DEV_PM_OPS(max6639_pm_ops, max6639_suspend, max6639_resume);
>   
>   static struct i2c_driver max6639_driver = {
>   	.class = I2C_CLASS_HWMON,
>   	.driver = {
>   		   .name = "max6639",
>   		   .pm = pm_sleep_ptr(&max6639_pm_ops),
> +		   .of_match_table = of_match_ptr(maxim_of_platform_match),
>   		   },
>   	.probe_new = max6639_probe,
>   	.id_table = max6639_id,

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