Message-ID: <aW0Ywij9SDXPDMIj@lizhi-Precision-Tower-5810>
Date: Sun, 18 Jan 2026 12:30:42 -0500
From: Frank Li <Frank.li@....com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Mayank Mahajan <mayankmahajan.x@....com>, corbet@....net,
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	priyanka.jain@....com, vikash.bansal@....com
Subject: Re: [PATCH v4 2/3] hwmon: (tmp108) Add support for P3T1035 and
 P3T2030

On Fri, Jan 16, 2026 at 04:36:59PM -0800, Guenter Roeck wrote:
> On 1/16/26 14:28, Frank Li wrote:
> > On Fri, Jan 16, 2026 at 05:05:53PM +0530, Mayank Mahajan wrote:
> > > Add support for the P3T1035 & P3T2030 temperature sensor. While mostly
> > > compatible with the TMP108, P3T1035 uses an 8-bit configuration register
> > > instead of the 16-bit layout used by TMP108. Updated driver to handle
> > > this difference during configuration read/write.
> > >
> > > Signed-off-by: Mayank Mahajan <mayankmahajan.x@....com>
> > > ---
> > > V1 -> V2:
> > > - Disabled hysteresis in is_visible function for P3T1035.
> > > - Added tables for conversion rate similar to the LM75 driver.
> > > - Implemented different bus access depending on the chip being used.
> > >     - Removed regmap for 8 bits; now we are using one regmap as before.
> > >     - Added read and write functions for i2c and i3c for use with regmap.
> > >     - Mapped the 8-bit configuration register to a 16 bit value for P3T1035.
> > > V2 -> V3:
> > > - Remove changes not relevant to adding a new device in the driver.
> > > - Address warnings due to incorrect usage of casting operations.
> > > - Remove the usage of P3T2030 as it's functionally identical to P3T1035.
> > > V3 -> V4:
> > > - Add GENMASK for getting mask for conversion rates.
> > > - Add static arrays for containing sample times for different sensors.
> > > - Remove redundant code such as checking for NULL pointer in probe.
> > > - Improve readability by removing double negation.
> > > - Remove type cast where not required; make reg_buf & val_buf local.
> > >
> > >   drivers/hwmon/Kconfig  |   2 +-
> > >   drivers/hwmon/tmp108.c | 203 +++++++++++++++++++++++++++++++++--------
> > >   2 files changed, 164 insertions(+), 41 deletions(-)
> > >
> > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > index 157678b821fc..31969bddc812 100644
> > > --- a/drivers/hwmon/Kconfig
> > > +++ b/drivers/hwmon/Kconfig
> > > @@ -2398,7 +2398,7 @@ config SENSORS_TMP108
> > >   	select REGMAP_I3C if I3C
> > >   	help
> > >   	  If you say yes here you get support for Texas Instruments TMP108
> > > -	  sensor chips and NXP P3T1085.
> > > +	  sensor chips, NXP temperature sensors P3T1035, P3T1085 and P3T2030.
> > >
> > >   	  This driver can also be built as a module. If so, the module
> > >   	  will be called tmp108.
> > > diff --git a/drivers/hwmon/tmp108.c b/drivers/hwmon/tmp108.c
> > > index 60a237cbedbc..d308e2aed18a 100644
> > > --- a/drivers/hwmon/tmp108.c
> > > +++ b/drivers/hwmon/tmp108.c
> > > @@ -17,9 +17,16 @@
> > >   #include <linux/regmap.h>
> > >   #include <linux/regulator/consumer.h>
> > >   #include <linux/slab.h>
> > > +#include <linux/util_macros.h>
> > >
> > >   #define	DRIVER_NAME "tmp108"
> > >
> > > +enum tmp108_hw_id {
> > > +	P3T1035_ID,		/* For sensors p3t1035 and p3t2030 */
> > > +	P3T1085_ID,
> > > +	TMP108_ID,
> > > +};
> > > +
> > >   #define	TMP108_REG_TEMP		0x00
> > >   #define	TMP108_REG_CONF		0x01
> > >   #define	TMP108_REG_TLOW		0x02
> > > @@ -61,6 +68,7 @@
> > >   #define TMP108_CONVRATE_1HZ		TMP108_CONF_CR0		/* Default */
> > >   #define TMP108_CONVRATE_4HZ		TMP108_CONF_CR1
> > >   #define TMP108_CONVRATE_16HZ		(TMP108_CONF_CR0|TMP108_CONF_CR1)
> > > +#define TMP108_CONVRATE_SHIFT		13
> > >
> > >   #define TMP108_CONF_HYSTERESIS_MASK	(TMP108_CONF_HYS0|TMP108_CONF_HYS1)
> > >   #define TMP108_HYSTERESIS_0C		0x0000
> > > @@ -70,12 +78,23 @@
> > >
> > >   #define TMP108_CONVERSION_TIME_MS	30	/* in milli-seconds */
> > >
> > > +#define TMP108_CONF_CR0_POS		13
> > > +#define TMP108_CONF_CR1_POS		14
> > > +#define TMP108_CONF_CONVRATE_FLD	GENMASK(TMP108_CONF_CR1_POS, TMP108_CONF_CR0_POS)
> > > +
> > >   struct tmp108 {
> > > -	struct regmap *regmap;
> > > -	u16 orig_config;
> > > -	unsigned long ready_time;
> > > +	struct regmap		*regmap;
> > > +	u16			orig_config;
> > > +	unsigned long		ready_time;
> >
> > don't mix format change in this patch.
> > Now prefer orignial format, just one space between type and field.
> >
> > > +	enum tmp108_hw_id	hw_id;
> > > +	bool			config_reg_16bits;
> > > +	ushort			*sample_times;
> > > +	size_t			n_sample_times;
> > >   };
> > >
> > > +ushort p3t1035_sample_times[] = {4000, 1000, 250, 125};
> > > +ushort tmp108_sample_times[] = {4000, 1000, 250, 63};
> > > +
> > >   /* convert 12-bit TMP108 register value to milliCelsius */
> > >   static inline int tmp108_temp_reg_to_mC(s16 val)
> > >   {
> > > @@ -101,21 +120,7 @@ static int tmp108_read(struct device *dev, enum hwmon_sensor_types type,
> > >   					  &regval);
> > >   			if (err < 0)
> > >   				return err;
> > > -			switch (regval & TMP108_CONF_CONVRATE_MASK) {
> > > -			case TMP108_CONVRATE_0P25HZ:
> > > -			default:
> > > -				*temp = 4000;
> > > -				break;
> > > -			case TMP108_CONVRATE_1HZ:
> > > -				*temp = 1000;
> > > -				break;
> > > -			case TMP108_CONVRATE_4HZ:
> > > -				*temp = 250;
> > > -				break;
> > > -			case TMP108_CONVRATE_16HZ:
> > > -				*temp = 63;
> > > -				break;
> > > -			}
> > > +			*temp = tmp108->sample_times[FIELD_GET(TMP108_CONF_CONVRATE_FLD, regval)];
> >
> > This code optimation need seperate patch.
> >
> No, There are now two ranges, not just one.

Previous code use swtich case to handle sample. now convert to use a map
array tmp108_sample_times[].

My means use a small patch convert existed switch case to map array firstly
, then add second range, which make code easy to review.

>
> > >   			return 0;
> > >   		}
> > >   		return -EOPNOTSUPP;
> > > @@ -192,22 +197,17 @@ static int tmp108_write(struct device *dev, enum hwmon_sensor_types type,
> > >   {
> > >   	struct tmp108 *tmp108 = dev_get_drvdata(dev);
> > >   	u32 regval, mask;
> > > +	u8 index;
> > >   	int err;
> > >
> > >   	if (type == hwmon_chip) {
> > >   		if (attr == hwmon_chip_update_interval) {
> > > -			if (temp < 156)
> > > -				mask = TMP108_CONVRATE_16HZ;
> > > -			else if (temp < 625)
> > > -				mask = TMP108_CONVRATE_4HZ;
> > > -			else if (temp < 2500)
> > > -				mask = TMP108_CONVRATE_1HZ;
> > > -			else
> > > -				mask = TMP108_CONVRATE_0P25HZ;
> > > +			index = find_closest_descending(temp, tmp108->sample_times,
> > > +							tmp108->n_sample_times);
> >
> > Need seperate patch for the code cleanup.
> >
>
> No. There are now two ranges, not just one. That is not a code cleanup,
> it is a change necessary to support multiple sets of ranges.


The smae here, this code just convert if else to helper function
find_closest_descending(), which is not related work, which add new
part support.

Frank
>
> Guenter
>
> > >   			return regmap_update_bits(tmp108->regmap,
> > >   						  TMP108_REG_CONF,
> > >   						  TMP108_CONF_CONVRATE_MASK,
> > > -						  mask);
> > > +						  FIELD_PREP(TMP108_CONF_CONVRATE_FLD, index));
> > >   		}
> > >   		return -EOPNOTSUPP;
> > >   	}
> > > @@ -251,6 +251,8 @@ static int tmp108_write(struct device *dev, enum hwmon_sensor_types type,
> > >   static umode_t tmp108_is_visible(const void *data, enum hwmon_sensor_types type,
> > >   				 u32 attr, int channel)
> > >   {
> > > +	const struct tmp108 *tmp108 = data;
> > > +
> > >   	if (type == hwmon_chip && attr == hwmon_chip_update_interval)
> > >   		return 0644;
> > >
> > > @@ -264,8 +266,11 @@ static umode_t tmp108_is_visible(const void *data, enum hwmon_sensor_types type,
> > >   		return 0444;
> > >   	case hwmon_temp_min:
> > >   	case hwmon_temp_max:
> > > +		return 0644;
> > >   	case hwmon_temp_min_hyst:
> > >   	case hwmon_temp_max_hyst:
> > > +		if (tmp108->hw_id == P3T1035_ID)
> > > +			return 0;
> > >   		return 0644;
> > >   	default:
> > >   		return 0;
> > > @@ -311,6 +316,106 @@ static bool tmp108_is_volatile_reg(struct device *dev, unsigned int reg)
> > >   	return reg == TMP108_REG_TEMP || reg == TMP108_REG_CONF;
> > >   }
> > >
> > > +static int tmp108_i2c_reg_read(void *context, unsigned int reg, unsigned int *val)
> > > +{
> > > +	struct i2c_client *client = context;
> > > +	struct tmp108 *tmp108 = i2c_get_clientdata(client);
> > > +	int ret;
> > > +
> > > +	if (reg == TMP108_REG_CONF && !tmp108->config_reg_16bits) {
> > > +		ret = i2c_smbus_read_byte_data(client, TMP108_REG_CONF);
> > > +		if (ret < 0)
> > > +			return ret;
> > > +		*val = ret << 8;
> > > +		return 0;
> > > +	}
> > > +
> > > +	ret = i2c_smbus_read_word_swapped(client, reg);
> > > +	if (ret < 0)
> > > +		return ret;
> > > +	*val = ret;
> > > +	return 0;
> > > +}
> > > +
> > > +static int tmp108_i2c_reg_write(void *context, unsigned int reg, unsigned int val)
> > > +{
> > > +	struct i2c_client *client = context;
> > > +	struct tmp108 *tmp108 = i2c_get_clientdata(client);
> > > +
> > > +	if (reg == TMP108_REG_CONF && !tmp108->config_reg_16bits)
> > > +		return i2c_smbus_write_byte_data(client, reg, val >> 8);
> > > +	return i2c_smbus_write_word_swapped(client, reg, val);
> > > +}
> > > +
> > > +static const struct regmap_bus tmp108_i2c_regmap_bus = {
> > > +	.reg_read = tmp108_i2c_reg_read,
> > > +	.reg_write = tmp108_i2c_reg_write,
> > > +};
> > > +
> > > +static int tmp108_i3c_reg_read(void *context, unsigned int reg, unsigned int *val)
> > > +{
> > > +	struct i3c_device *i3cdev = context;
> > > +	struct tmp108 *tmp108 = i3cdev_get_drvdata(i3cdev);
> > > +	u8 reg_buf[1], val_buf[2];
> > > +	struct i3c_xfer xfers[] = {
> > > +		{
> > > +			.rnw = false,
> > > +			.len = 1,
> > > +			.data.out = reg_buf,
> > > +		},
> > > +		{
> > > +			.rnw = true,
> > > +			.len = 2,
> > > +			.data.in = val_buf,
> > > +		},
> > > +	};
> > > +	int ret;
> > > +
> > > +	reg_buf[0] = reg;
> > > +
> > > +	if (reg == TMP108_REG_CONF && !tmp108->config_reg_16bits)
> > > +		xfers[1].len--;
> > > +
> > > +	ret = i3c_device_do_xfers(i3cdev, xfers, 2, I3C_SDR);
> > > +	if (ret < 0)
> > > +		return ret;
> > > +
> > > +	*val = val_buf[0] << 8;
> > > +	if (reg != TMP108_REG_CONF || tmp108->config_reg_16bits)
> > > +		*val |= val_buf[1];
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int tmp108_i3c_reg_write(void *context, unsigned int reg, unsigned int val)
> > > +{
> > > +	struct i3c_device *i3cdev = context;
> > > +	struct tmp108 *tmp108 = i3cdev_get_drvdata(i3cdev);
> > > +	u8 val_buf[3];
> > > +	struct i3c_xfer xfers[] = {
> > > +		{
> > > +			.rnw = false,
> > > +			.len = 3,
> > > +			.data.out = val_buf,
> > > +		},
> > > +	};
> > > +
> > > +	val_buf[0] = reg;
> > > +	val_buf[1] = (val >> 8) & 0xff;
> > > +
> > > +	if (reg == TMP108_REG_CONF && !tmp108->config_reg_16bits)
> > > +		xfers[0].len--;
> > > +	else
> > > +		val_buf[2] = val & 0xff;
> > > +
> > > +	return i3c_device_do_xfers(i3cdev, xfers, 1, I3C_SDR);
> > > +}
> > > +
> > > +static const struct regmap_bus tmp108_i3c_regmap_bus = {
> > > +	.reg_read = tmp108_i3c_reg_read,
> > > +	.reg_write = tmp108_i3c_reg_write,
> > > +};
> > > +
> > >   static const struct regmap_config tmp108_regmap_config = {
> > >   	.reg_bits = 8,
> > >   	.val_bits = 16,
> > > @@ -323,7 +428,8 @@ static const struct regmap_config tmp108_regmap_config = {
> > >   	.use_single_write = true,
> > >   };
> > >
> > > -static int tmp108_common_probe(struct device *dev, struct regmap *regmap, char *name)
> > > +static int tmp108_common_probe(struct device *dev, struct regmap *regmap, char *name,
> > > +			       enum tmp108_hw_id hw_id)
> > >   {
> > >   	struct device *hwmon_dev;
> > >   	struct tmp108 *tmp108;
> > > @@ -340,6 +446,15 @@ static int tmp108_common_probe(struct device *dev, struct regmap *regmap, char *
> > >
> > >   	dev_set_drvdata(dev, tmp108);
> > >   	tmp108->regmap = regmap;
> > > +	tmp108->hw_id = hw_id;
> > > +	tmp108->config_reg_16bits = (hw_id == P3T1035_ID) ? false : true;
> > > +	if (hw_id == P3T1035_ID) {
> > > +		tmp108->sample_times = p3t1035_sample_times;
> > > +		tmp108->n_sample_times = ARRAY_SIZE(p3t1035_sample_times);
> > > +	} else {
> > > +		tmp108->sample_times = tmp108_sample_times;
> > > +		tmp108->n_sample_times = ARRAY_SIZE(tmp108_sample_times);
> > > +	}
> > >
> > >   	err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &config);
> > >   	if (err < 0) {
> > > @@ -351,7 +466,6 @@ static int tmp108_common_probe(struct device *dev, struct regmap *regmap, char *
> > >   	/* Only continuous mode is supported. */
> > >   	config &= ~TMP108_CONF_MODE_MASK;
> > >   	config |= TMP108_MODE_CONTINUOUS;
> > > -
> > >   	/* Only comparator mode is supported. */
> > >   	config &= ~TMP108_CONF_TM;
> > >
> > > @@ -384,17 +498,20 @@ static int tmp108_probe(struct i2c_client *client)
> > >   {
> > >   	struct device *dev = &client->dev;
> > >   	struct regmap *regmap;
> > > +	enum tmp108_hw_id hw_id;
> > >
> > >   	if (!i2c_check_functionality(client->adapter,
> > > -				     I2C_FUNC_SMBUS_WORD_DATA))
> > > +				     I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
> > >   		return dev_err_probe(dev, -ENODEV,
> > >   				     "adapter doesn't support SMBus word transactions\n");
> > >
> > > -	regmap = devm_regmap_init_i2c(client, &tmp108_regmap_config);
> > > +	regmap = devm_regmap_init(dev, &tmp108_i2c_regmap_bus, client, &tmp108_regmap_config);
> > >   	if (IS_ERR(regmap))
> > >   		return dev_err_probe(dev, PTR_ERR(regmap), "regmap init failed");
> > >
> > > -	return tmp108_common_probe(dev, regmap, client->name);
> > > +	hw_id = (unsigned long)i2c_get_match_data(client);
> > > +
> > > +	return tmp108_common_probe(dev, regmap, client->name, hw_id);
> > >   }
> > >
> > >   static int tmp108_suspend(struct device *dev)
> > > @@ -420,15 +537,17 @@ static int tmp108_resume(struct device *dev)
> > >   static DEFINE_SIMPLE_DEV_PM_OPS(tmp108_dev_pm_ops, tmp108_suspend, tmp108_resume);
> > >
> > >   static const struct i2c_device_id tmp108_i2c_ids[] = {
> > > -	{ "p3t1085" },
> > > -	{ "tmp108" },
> > > -	{ }
> > > +	{ "p3t1035", P3T1035_ID },
> > > +	{ "p3t1085", P3T1085_ID },
> > > +	{ "tmp108", TMP108_ID },
> > > +	{}
> > >   };
> > >   MODULE_DEVICE_TABLE(i2c, tmp108_i2c_ids);
> > >
> > >   static const struct of_device_id tmp108_of_ids[] = {
> > > -	{ .compatible = "nxp,p3t1085", },
> > > -	{ .compatible = "ti,tmp108", },
> > > +	{ .compatible = "nxp,p3t1035", .data = (void *)(uintptr_t)P3T1035_ID },
> > > +	{ .compatible = "nxp,p3t1085", .data = (void *)(uintptr_t)P3T1085_ID },
> > > +	{ .compatible = "ti,tmp108", .data = (void *)(uintptr_t)TMP108_ID },
> >
> > Do not use device ID, define struct drvdata
> >
> > 	struct tmp108_drvdata
> > 	{
> > 		.samples = p3t1035_sample_times;
> > 		.reg_width = 16,
> > 		...
> > 	}
> >
> > Frank
> > >   	{}
> > >   };
> > >   MODULE_DEVICE_TABLE(of, tmp108_of_ids);
> > > @@ -444,7 +563,8 @@ static struct i2c_driver tmp108_driver = {
> > >   };
> > >
> > >   static const struct i3c_device_id p3t1085_i3c_ids[] = {
> > > -	I3C_DEVICE(0x011b, 0x1529, NULL),
> > > +	I3C_DEVICE(0x011B, 0x1529, (void *)P3T1085_ID),
> > > +	I3C_DEVICE(0x011B, 0x152B, (void *)P3T1035_ID),
> > >   	{}
> > >   };
> > >   MODULE_DEVICE_TABLE(i3c, p3t1085_i3c_ids);
> > > @@ -453,13 +573,16 @@ static int p3t1085_i3c_probe(struct i3c_device *i3cdev)
> > >   {
> > >   	struct device *dev = i3cdev_to_dev(i3cdev);
> > >   	struct regmap *regmap;
> > > +	const struct i3c_device_id *id;
> > >
> > > -	regmap = devm_regmap_init_i3c(i3cdev, &tmp108_regmap_config);
> > > +	regmap = devm_regmap_init(dev, &tmp108_i3c_regmap_bus, i3cdev, &tmp108_regmap_config);
> > >   	if (IS_ERR(regmap))
> > >   		return dev_err_probe(dev, PTR_ERR(regmap),
> > >   				     "Failed to register i3c regmap\n");
> > >
> > > -	return tmp108_common_probe(dev, regmap, "p3t1085_i3c");
> > > +	id = i3c_device_match_id(i3cdev, p3t1085_i3c_ids);
> > > +
> > > +	return tmp108_common_probe(dev, regmap, "p3t1085_i3c", (unsigned long)id->data);
> > >   }
> > >
> > >   static struct i3c_driver p3t1085_driver = {
> > > --
> > > 2.34.1
>

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