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Date:   Sun, 10 Oct 2021 11:13:44 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Oskar Senft <osk@...gle.com>, Jean Delvare <jdelvare@...e.com>,
        Rob Herring <robh+dt@...nel.org>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v6 2/2] hwmon: (nct7802) Make temperature/voltage sensors
 configurable

On 10/9/21 8:31 PM, Oskar Senft wrote:
> This change allows LTD and RTD inputs to be configured via
> device tree bindings. If the DT bindings are not present or
> invalid, the input configuration is not modified and left at
> HW defaults.
> 
> Signed-off-by: Oskar Senft <osk@...gle.com>

For my reference:

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

Thanks,
Guenter

> ---
> Changes from PATCH v5:
> - Removed unused "found_channel_config" variable.
> - Initialize mode_mask and mode_val to defaults.
> ---
>   drivers/hwmon/nct7802.c | 129 ++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 125 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwmon/nct7802.c b/drivers/hwmon/nct7802.c
> index 604af2f6103a..d56f78327619 100644
> --- a/drivers/hwmon/nct7802.c
> +++ b/drivers/hwmon/nct7802.c
> @@ -51,6 +51,23 @@ static const u8 REG_VOLTAGE_LIMIT_MSB_SHIFT[2][5] = {
>   #define REG_CHIP_ID		0xfe
>   #define REG_VERSION_ID		0xff
>   
> +/*
> + * Resistance temperature detector (RTD) modes according to 7.2.32 Mode
> + * Selection Register
> + */
> +#define RTD_MODE_CURRENT	0x1
> +#define RTD_MODE_THERMISTOR	0x2
> +#define RTD_MODE_VOLTAGE	0x3
> +
> +#define MODE_RTD_MASK		0x3
> +#define MODE_LTD_EN		0x40
> +
> +/*
> + * Bit offset for sensors modes in REG_MODE.
> + * Valid for index 0..2, indicating RTD1..3.
> + */
> +#define MODE_BIT_OFFSET_RTD(index) ((index) * 2)
> +
>   /*
>    * Data structures and manipulation thereof
>    */
> @@ -1038,7 +1055,112 @@ static const struct regmap_config nct7802_regmap_config = {
>   	.volatile_reg = nct7802_regmap_is_volatile,
>   };
>   
> -static int nct7802_init_chip(struct nct7802_data *data)
> +static int nct7802_get_channel_config(struct device *dev,
> +				      struct device_node *node, u8 *mode_mask,
> +				      u8 *mode_val)
> +{
> +	u32 reg;
> +	const char *type_str, *md_str;
> +	u8 md;
> +
> +	if (!node->name || of_node_cmp(node->name, "channel"))
> +		return 0;
> +
> +	if (of_property_read_u32(node, "reg", &reg)) {
> +		dev_err(dev, "Could not read reg value for '%s'\n",
> +			node->full_name);
> +		return -EINVAL;
> +	}
> +
> +	if (reg > 3) {
> +		dev_err(dev, "Invalid reg (%u) in '%s'\n", reg,
> +			node->full_name);
> +		return -EINVAL;
> +	}
> +
> +	if (reg == 0) {
> +		if (!of_device_is_available(node))
> +			*mode_val &= ~MODE_LTD_EN;
> +		else
> +			*mode_val |= MODE_LTD_EN;
> +		*mode_mask |= MODE_LTD_EN;
> +		return 0;
> +	}
> +
> +	/* At this point we have reg >= 1 && reg <= 3 */
> +
> +	if (!of_device_is_available(node)) {
> +		*mode_val &= ~(MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1));
> +		*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
> +		return 0;
> +	}
> +
> +	if (of_property_read_string(node, "sensor-type", &type_str)) {
> +		dev_err(dev, "No type for '%s'\n", node->full_name);
> +		return -EINVAL;
> +	}
> +
> +	if (!strcmp(type_str, "voltage")) {
> +		*mode_val |= (RTD_MODE_VOLTAGE & MODE_RTD_MASK)
> +			     << MODE_BIT_OFFSET_RTD(reg - 1);
> +		*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
> +		return 0;
> +	}
> +
> +	if (strcmp(type_str, "temperature")) {
> +		dev_err(dev, "Invalid type '%s' for '%s'\n", type_str,
> +			node->full_name);
> +		return -EINVAL;
> +	}
> +
> +	if (reg == 3) {
> +		/* RTD3 only supports thermistor mode */
> +		md = RTD_MODE_THERMISTOR;
> +	} else {
> +		if (of_property_read_string(node, "temperature-mode",
> +					    &md_str)) {
> +			dev_err(dev, "No mode for '%s'\n", node->full_name);
> +			return -EINVAL;
> +		}
> +
> +		if (!strcmp(md_str, "thermal-diode"))
> +			md = RTD_MODE_CURRENT;
> +		else if (!strcmp(md_str, "thermistor"))
> +			md = RTD_MODE_THERMISTOR;
> +		else {
> +			dev_err(dev, "Invalid mode '%s' for '%s'\n", md_str,
> +				node->full_name);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	*mode_val |= (md & MODE_RTD_MASK) << MODE_BIT_OFFSET_RTD(reg - 1);
> +	*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
> +
> +	return 0;
> +}
> +
> +static int nct7802_configure_channels(struct device *dev,
> +				      struct nct7802_data *data)
> +{
> +	/* Enable local temperature sensor by default */
> +	u8 mode_mask = MODE_LTD_EN, mode_val = MODE_LTD_EN;
> +	struct device_node *node;
> +	int err;
> +
> +	if (dev->of_node) {
> +		for_each_child_of_node(dev->of_node, node) {
> +			err = nct7802_get_channel_config(dev, node, &mode_mask,
> +							 &mode_val);
> +			if (err)
> +				return err;
> +		}
> +	}
> +
> +	return regmap_update_bits(data->regmap, REG_MODE, mode_mask, mode_val);
> +}
> +
> +static int nct7802_init_chip(struct device *dev, struct nct7802_data *data)
>   {
>   	int err;
>   
> @@ -1047,8 +1169,7 @@ static int nct7802_init_chip(struct nct7802_data *data)
>   	if (err)
>   		return err;
>   
> -	/* Enable local temperature sensor */
> -	err = regmap_update_bits(data->regmap, REG_MODE, 0x40, 0x40);
> +	err = nct7802_configure_channels(dev, data);
>   	if (err)
>   		return err;
>   
> @@ -1074,7 +1195,7 @@ static int nct7802_probe(struct i2c_client *client)
>   	mutex_init(&data->access_lock);
>   	mutex_init(&data->in_alarm_lock);
>   
> -	ret = nct7802_init_chip(data);
> +	ret = nct7802_init_chip(dev, data);
>   	if (ret < 0)
>   		return ret;
>   
> 

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