* [PATCH v1] hwmon: (lm75) Add support for Nuvoton NCT7715
@ 2026-09-07 8:08 hsyemail2
2026-09-07 15:29 ` Guenter Roeck
0 siblings, 1 reply; 5+ messages in thread
From: hsyemail2 @ 2026-09-07 8:08 UTC (permalink / raw)
To: Guenter Roeck, linux-hwmon
Cc: Sheng-Yuan Huang, Rob Herring, Krzysztof Kozlowski, Conor Dooley,
Jonathan Corbet, Shuah Khan, Jean Delvare, devicetree,
linux-kernel, linux-doc
From: Sheng-Yuan Huang <syhuang3@nuvoton.com>
The Nuvoton NCT7715 is compatible with the LM75 temperature and
limit register layout, but its 16-bit configuration register is
transmitted most-significant byte first. Add support for the NCT7715,
including byte-swapped SMBus accesses for its configuration register.
Handle its conversion-rate field and shutdown bit separately, since
their bit positions differ from the standard LM75 layout.
Signed-off-by: Sheng-Yuan Huang <syhuang3@nuvoton.com>
---
.../devicetree/bindings/hwmon/lm75.yaml | 1 +
Documentation/hwmon/lm75.rst | 6 ++
drivers/hwmon/lm75.c | 57 ++++++++++++++++++-
3 files changed, 62 insertions(+), 2 deletions(-)
diff --git a/Documentation/devicetree/bindings/hwmon/lm75.yaml b/Documentation/devicetree/bindings/hwmon/lm75.yaml
index b48bf3fd721f..832a8c5d83e9 100644
--- a/Documentation/devicetree/bindings/hwmon/lm75.yaml
+++ b/Documentation/devicetree/bindings/hwmon/lm75.yaml
@@ -31,6 +31,7 @@ properties:
- nxp,p3t1750
- nxp,p3t1755
- nxp,pct2075
+ - nuvoton,nct7715
- st,stds75
- st,stlm75
- microchip,tcn75
diff --git a/Documentation/hwmon/lm75.rst b/Documentation/hwmon/lm75.rst
index ca46754e028b..fac0b8f29ddc 100644
--- a/Documentation/hwmon/lm75.rst
+++ b/Documentation/hwmon/lm75.rst
@@ -150,6 +150,12 @@ Supported chips:
https://ams.com/documents/20143/36005/AS6200_DS000449_4-00.pdf
+ * Nuvoton NCT7715
+
+ Prefix: 'nct7715'
+
+ Addresses scanned: none
+
Author: Frodo Looijaard <frodol@dds.nl>
Description
diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
index 2d2d752aeac9..0b55f6b7c68d 100644
--- a/drivers/hwmon/lm75.c
+++ b/drivers/hwmon/lm75.c
@@ -39,6 +39,7 @@ enum lm75_type { /* keep sorted in alphabetical order */
max6626,
max31725,
mcp980x,
+ nct7715,
p3t1750,
p3t1755,
pct2075,
@@ -107,6 +108,15 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
#define LM75_REG_MAX 0x03
#define PCT2075_REG_IDLE 0x04
+#define NCT7715_CONFIG_RESOLUTION_12_BIT GENMASK(14, 13)
+#define NCT7715_CONFIG_SHUTDOWN BIT(8)
+#define NCT7715_CONFIG_CONVERSION_RATE_MASK GENMASK(7, 6)
+#define NCT7715_CONFIG_EXTENDED_MODE BIT(4)
+#define NCT7715_CONFIG_RATE_0_25HZ 0
+#define NCT7715_CONFIG_RATE_1HZ BIT(6)
+#define NCT7715_CONFIG_RATE_4HZ BIT(7)
+#define NCT7715_CONFIG_RATE_8HZ GENMASK(7, 6)
+
struct lm75_data {
const char *label;
struct regmap *regmap;
@@ -122,6 +132,10 @@ struct lm75_data {
/*-----------------------------------------------------------------------*/
static const u8 lm75_sample_set_masks[] = { 0 << 5, 1 << 5, 2 << 5, 3 << 5 };
+static const u16 nct7715_sample_set_masks[] = {
+ NCT7715_CONFIG_RATE_8HZ, NCT7715_CONFIG_RATE_4HZ,
+ NCT7715_CONFIG_RATE_1HZ, NCT7715_CONFIG_RATE_0_25HZ
+};
#define LM75_ALERT_POLARITY_HIGH_8_BIT (BIT(2))
#define LM75_ALERT_POLARITY_HIGH_16_BIT (BIT(2) << 8)
@@ -259,6 +273,15 @@ static const struct lm75_params device_params[] = {
.sample_times = (unsigned int []){ 30, 60, 120, 240 },
.resolutions = (u8 []) {9, 10, 11, 12 },
},
+ [nct7715] = {
+ .config_reg_16bits = true,
+ .set_mask = NCT7715_CONFIG_RESOLUTION_12_BIT,
+ .clr_mask = NCT7715_CONFIG_EXTENDED_MODE,
+ .default_resolution = 12,
+ .default_sample_time = 250,
+ .num_sample_times = 4,
+ .sample_times = (unsigned int []){ 125, 250, 1000, 4000 },
+ },
[tmp100] = {
.set_mask = 3 << 5, /* 12-bit mode */
.clr_mask = 1 << 7, /* not one-shot mode */
@@ -354,6 +377,11 @@ static inline long lm75_reg_to_mc(s16 temp, u8 resolution)
static inline int lm75_write_config(struct lm75_data *data, u16 set_mask,
u16 clr_mask)
{
+ if (data->kind == nct7715)
+ return regmap_update_bits(data->regmap, LM75_REG_CONF,
+ clr_mask | set_mask | NCT7715_CONFIG_SHUTDOWN,
+ set_mask);
+
return regmap_update_bits(data->regmap, LM75_REG_CONF,
clr_mask | set_mask | LM75_SHUTDOWN, set_mask);
}
@@ -486,6 +514,13 @@ static int lm75_update_interval(struct device *dev, long val)
if (data->params->resolutions)
data->resolution = data->params->resolutions[index];
break;
+ case nct7715:
+ err = lm75_write_config(data, nct7715_sample_set_masks[index],
+ NCT7715_CONFIG_CONVERSION_RATE_MASK);
+ if (err)
+ return err;
+ data->sample_time = data->params->sample_times[index];
+ break;
case tmp112:
case as6200:
err = regmap_update_bits(data->regmap, LM75_REG_CONF,
@@ -609,6 +644,8 @@ static int lm75_i2c_reg_read(void *context, unsigned int reg, unsigned int *val)
if (reg == LM75_REG_CONF) {
if (!data->params->config_reg_16bits)
ret = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
+ else if (data->kind == nct7715)
+ ret = i2c_smbus_read_word_swapped(client, LM75_REG_CONF);
else
ret = i2c_smbus_read_word_data(client, LM75_REG_CONF);
} else {
@@ -628,8 +665,11 @@ static int lm75_i2c_reg_write(void *context, unsigned int reg, unsigned int val)
if (reg == PCT2075_REG_IDLE ||
(reg == LM75_REG_CONF && !data->params->config_reg_16bits))
return i2c_smbus_write_byte_data(client, reg, val);
- else if (reg == LM75_REG_CONF)
+ else if (reg == LM75_REG_CONF) {
+ if (data->kind == nct7715)
+ return i2c_smbus_write_word_swapped(client, reg, val);
return i2c_smbus_write_word_data(client, reg, val);
+ }
return i2c_smbus_write_word_swapped(client, reg, val);
}
@@ -848,6 +888,7 @@ static const struct i2c_device_id lm75_i2c_ids[] = {
{ .name = "max31725", .driver_data = max31725 },
{ .name = "max31726", .driver_data = max31725 },
{ .name = "mcp980x", .driver_data = mcp980x },
+ { .name = "nct7715", .driver_data = nct7715 },
{ .name = "p3t1750", .driver_data = p3t1750 },
{ .name = "p3t1755", .driver_data = p3t1755 },
{ .name = "pct2075", .driver_data = pct2075 },
@@ -972,6 +1013,10 @@ static const struct of_device_id lm75_of_match[] = {
.compatible = "nxp,pct2075",
.data = (void *)pct2075
},
+ {
+ .compatible = "nuvoton,nct7715",
+ .data = (void *)nct7715
+ },
{
.compatible = "st,stds75",
.data = (void *)stds75
@@ -1129,13 +1174,21 @@ static int lm75_suspend(struct device *dev)
{
struct lm75_data *data = dev_get_drvdata(dev);
- return regmap_update_bits(data->regmap, LM75_REG_CONF, LM75_SHUTDOWN, LM75_SHUTDOWN);
+ if (data->kind == nct7715)
+ return regmap_update_bits(data->regmap, LM75_REG_CONF,
+ NCT7715_CONFIG_SHUTDOWN,
+ NCT7715_CONFIG_SHUTDOWN);
+ return regmap_update_bits(data->regmap, LM75_REG_CONF,
+ LM75_SHUTDOWN, LM75_SHUTDOWN);
}
static int lm75_resume(struct device *dev)
{
struct lm75_data *data = dev_get_drvdata(dev);
+ if (data->kind == nct7715)
+ return regmap_update_bits(data->regmap, LM75_REG_CONF,
+ NCT7715_CONFIG_SHUTDOWN, 0);
return regmap_update_bits(data->regmap, LM75_REG_CONF, LM75_SHUTDOWN, 0);
}
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v1] hwmon: (lm75) Add support for Nuvoton NCT7715
2026-09-07 8:08 [PATCH v1] hwmon: (lm75) Add support for Nuvoton NCT7715 hsyemail2
@ 2026-09-07 15:29 ` Guenter Roeck
2026-09-09 7:10 ` Sheng-Yuan Huang
0 siblings, 1 reply; 5+ messages in thread
From: Guenter Roeck @ 2026-09-07 15:29 UTC (permalink / raw)
To: hsyemail2, linux-hwmon
Cc: Sheng-Yuan Huang, Rob Herring, Krzysztof Kozlowski, Conor Dooley,
Jonathan Corbet, Shuah Khan, Jean Delvare, devicetree,
linux-kernel, linux-doc
On 9/7/26 01:08, hsyemail2@gmail.com wrote:
> From: Sheng-Yuan Huang <syhuang3@nuvoton.com>
>
> The Nuvoton NCT7715 is compatible with the LM75 temperature and
> limit register layout, but its 16-bit configuration register is
> transmitted most-significant byte first. Add support for the NCT7715,
> including byte-swapped SMBus accesses for its configuration register.
>
> Handle its conversion-rate field and shutdown bit separately, since
> their bit positions differ from the standard LM75 layout.
>
I don't think so. See below.
> Signed-off-by: Sheng-Yuan Huang <syhuang3@nuvoton.com>
> ---
> .../devicetree/bindings/hwmon/lm75.yaml | 1 +
> Documentation/hwmon/lm75.rst | 6 ++
> drivers/hwmon/lm75.c | 57 ++++++++++++++++++-
> 3 files changed, 62 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/hwmon/lm75.yaml b/Documentation/devicetree/bindings/hwmon/lm75.yaml
> index b48bf3fd721f..832a8c5d83e9 100644
> --- a/Documentation/devicetree/bindings/hwmon/lm75.yaml
> +++ b/Documentation/devicetree/bindings/hwmon/lm75.yaml
> @@ -31,6 +31,7 @@ properties:
> - nxp,p3t1750
> - nxp,p3t1755
> - nxp,pct2075
> + - nuvoton,nct7715
> - st,stds75
> - st,stlm75
> - microchip,tcn75
> diff --git a/Documentation/hwmon/lm75.rst b/Documentation/hwmon/lm75.rst
> index ca46754e028b..fac0b8f29ddc 100644
> --- a/Documentation/hwmon/lm75.rst
> +++ b/Documentation/hwmon/lm75.rst
> @@ -150,6 +150,12 @@ Supported chips:
>
> https://ams.com/documents/20143/36005/AS6200_DS000449_4-00.pdf
>
> + * Nuvoton NCT7715
> +
> + Prefix: 'nct7715'
> +
> + Addresses scanned: none
> +
> Author: Frodo Looijaard <frodol@dds.nl>
>
> Description
> diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
> index 2d2d752aeac9..0b55f6b7c68d 100644
> --- a/drivers/hwmon/lm75.c
> +++ b/drivers/hwmon/lm75.c
> @@ -39,6 +39,7 @@ enum lm75_type { /* keep sorted in alphabetical order */
> max6626,
> max31725,
> mcp980x,
> + nct7715,
> p3t1750,
> p3t1755,
> pct2075,
> @@ -107,6 +108,15 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
> #define LM75_REG_MAX 0x03
> #define PCT2075_REG_IDLE 0x04
>
> +#define NCT7715_CONFIG_RESOLUTION_12_BIT GENMASK(14, 13)
> +#define NCT7715_CONFIG_SHUTDOWN BIT(8)
> +#define NCT7715_CONFIG_CONVERSION_RATE_MASK GENMASK(7, 6)
> +#define NCT7715_CONFIG_EXTENDED_MODE BIT(4)
> +#define NCT7715_CONFIG_RATE_0_25HZ 0
> +#define NCT7715_CONFIG_RATE_1HZ BIT(6)
> +#define NCT7715_CONFIG_RATE_4HZ BIT(7)
> +#define NCT7715_CONFIG_RATE_8HZ GENMASK(7, 6)
> +
> struct lm75_data {
> const char *label;
> struct regmap *regmap;
> @@ -122,6 +132,10 @@ struct lm75_data {
> /*-----------------------------------------------------------------------*/
>
> static const u8 lm75_sample_set_masks[] = { 0 << 5, 1 << 5, 2 << 5, 3 << 5 };
> +static const u16 nct7715_sample_set_masks[] = {
> + NCT7715_CONFIG_RATE_8HZ, NCT7715_CONFIG_RATE_4HZ,
> + NCT7715_CONFIG_RATE_1HZ, NCT7715_CONFIG_RATE_0_25HZ
> +};
>
> #define LM75_ALERT_POLARITY_HIGH_8_BIT (BIT(2))
> #define LM75_ALERT_POLARITY_HIGH_16_BIT (BIT(2) << 8)
> @@ -259,6 +273,15 @@ static const struct lm75_params device_params[] = {
> .sample_times = (unsigned int []){ 30, 60, 120, 240 },
> .resolutions = (u8 []) {9, 10, 11, 12 },
> },
> + [nct7715] = {
> + .config_reg_16bits = true,
> + .set_mask = NCT7715_CONFIG_RESOLUTION_12_BIT,
> + .clr_mask = NCT7715_CONFIG_EXTENDED_MODE,
> + .default_resolution = 12,
> + .default_sample_time = 250,
> + .num_sample_times = 4,
> + .sample_times = (unsigned int []){ 125, 250, 1000, 4000 },
> + },
> [tmp100] = {
> .set_mask = 3 << 5, /* 12-bit mode */
> .clr_mask = 1 << 7, /* not one-shot mode */
> @@ -354,6 +377,11 @@ static inline long lm75_reg_to_mc(s16 temp, u8 resolution)
> static inline int lm75_write_config(struct lm75_data *data, u16 set_mask,
> u16 clr_mask)
> {
> + if (data->kind == nct7715)
> + return regmap_update_bits(data->regmap, LM75_REG_CONF,
> + clr_mask | set_mask | NCT7715_CONFIG_SHUTDOWN,
> + set_mask);
> +
> return regmap_update_bits(data->regmap, LM75_REG_CONF,
> clr_mask | set_mask | LM75_SHUTDOWN, set_mask);
> }
> @@ -486,6 +514,13 @@ static int lm75_update_interval(struct device *dev, long val)
> if (data->params->resolutions)
> data->resolution = data->params->resolutions[index];
> break;
> + case nct7715:
> + err = lm75_write_config(data, nct7715_sample_set_masks[index],
> + NCT7715_CONFIG_CONVERSION_RATE_MASK);
> + if (err)
> + return err;
> + data->sample_time = data->params->sample_times[index];
> + break;
> case tmp112:
> case as6200:
> err = regmap_update_bits(data->regmap, LM75_REG_CONF,
> @@ -609,6 +644,8 @@ static int lm75_i2c_reg_read(void *context, unsigned int reg, unsigned int *val)
> if (reg == LM75_REG_CONF) {
> if (!data->params->config_reg_16bits)
> ret = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
> + else if (data->kind == nct7715)
> + ret = i2c_smbus_read_word_swapped(client, LM75_REG_CONF);
> else
> ret = i2c_smbus_read_word_data(client, LM75_REG_CONF);
> } else {
> @@ -628,8 +665,11 @@ static int lm75_i2c_reg_write(void *context, unsigned int reg, unsigned int val)
> if (reg == PCT2075_REG_IDLE ||
> (reg == LM75_REG_CONF && !data->params->config_reg_16bits))
> return i2c_smbus_write_byte_data(client, reg, val);
> - else if (reg == LM75_REG_CONF)
> + else if (reg == LM75_REG_CONF) {
> + if (data->kind == nct7715)
> + return i2c_smbus_write_word_swapped(client, reg, val);
This code is double swapping. The calling code swaps (bit settings),
regmap calls this function, where the word is swapped again.
Guenter
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v1] hwmon: (lm75) Add support for Nuvoton NCT7715
2026-09-07 15:29 ` Guenter Roeck
@ 2026-09-09 7:10 ` Sheng-Yuan Huang
2026-09-09 14:02 ` Guenter Roeck
0 siblings, 1 reply; 5+ messages in thread
From: Sheng-Yuan Huang @ 2026-09-09 7:10 UTC (permalink / raw)
To: Guenter Roeck, linux-hwmon
Cc: Sheng-Yuan Huang, Rob Herring, Krzysztof Kozlowski, Conor Dooley,
Jonathan Corbet, Shuah Khan, Jean Delvare, devicetree,
linux-kernel, linux-doc
Thank you for the review. I may have misunderstood which conversion
you are referring to, so I would like to clarify both parts.
If this refers to the NCT7715_CONFIG_* masks, they use the logical bit
positions of the 16-bit configuration register defined by the
NCT7715 specification. They are not pre-swapped for the SMBus word
byte order.
If this refers to the I2C accessors, the NCT7715 transfers its 16-bit
configuration register MSB first. The lm75 regmap bus uses
reg_read/reg_write callbacks. In this path, regmap passes the logical
register value to the callbacks, and i2c_smbus_*_word_swapped()
performs the conversion between that value and the SMBus word byte
order.
I verified this on hardware by changing update_interval. i2cget shows
0xe060, 0xa060, 0x6060, and 0x2060 for 125, 250, 1000, and 4000 ms,
respectively. After accounting for the SMBus word byte order, these
are logical values 0x60e0, 0x60a0, 0x6060, and 0x6020. In each case,
only the NCT7715 conversion-rate field, bits [7:6], is changed.
Guenter Roeck <linux@roeck-us.net> 於 2026年9月7日週一 下午11:30寫道：
>
> On 9/7/26 01:08, hsyemail2@gmail.com wrote:
> > From: Sheng-Yuan Huang <syhuang3@nuvoton.com>
> >
> > The Nuvoton NCT7715 is compatible with the LM75 temperature and
> > limit register layout, but its 16-bit configuration register is
> > transmitted most-significant byte first. Add support for the NCT7715,
> > including byte-swapped SMBus accesses for its configuration register.
> >
> > Handle its conversion-rate field and shutdown bit separately, since
> > their bit positions differ from the standard LM75 layout.
> >
> I don't think so. See below.
>
> > Signed-off-by: Sheng-Yuan Huang <syhuang3@nuvoton.com>
> > ---
> > .../devicetree/bindings/hwmon/lm75.yaml | 1 +
> > Documentation/hwmon/lm75.rst | 6 ++
> > drivers/hwmon/lm75.c | 57 ++++++++++++++++++-
> > 3 files changed, 62 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/hwmon/lm75.yaml b/Documentation/devicetree/bindings/hwmon/lm75.yaml
> > index b48bf3fd721f..832a8c5d83e9 100644
> > --- a/Documentation/devicetree/bindings/hwmon/lm75.yaml
> > +++ b/Documentation/devicetree/bindings/hwmon/lm75.yaml
> > @@ -31,6 +31,7 @@ properties:
> > - nxp,p3t1750
> > - nxp,p3t1755
> > - nxp,pct2075
> > + - nuvoton,nct7715
> > - st,stds75
> > - st,stlm75
> > - microchip,tcn75
> > diff --git a/Documentation/hwmon/lm75.rst b/Documentation/hwmon/lm75.rst
> > index ca46754e028b..fac0b8f29ddc 100644
> > --- a/Documentation/hwmon/lm75.rst
> > +++ b/Documentation/hwmon/lm75.rst
> > @@ -150,6 +150,12 @@ Supported chips:
> >
> > https://ams.com/documents/20143/36005/AS6200_DS000449_4-00.pdf
> >
> > + * Nuvoton NCT7715
> > +
> > + Prefix: 'nct7715'
> > +
> > + Addresses scanned: none
> > +
> > Author: Frodo Looijaard <frodol@dds.nl>
> >
> > Description
> > diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
> > index 2d2d752aeac9..0b55f6b7c68d 100644
> > --- a/drivers/hwmon/lm75.c
> > +++ b/drivers/hwmon/lm75.c
> > @@ -39,6 +39,7 @@ enum lm75_type { /* keep sorted in alphabetical order */
> > max6626,
> > max31725,
> > mcp980x,
> > + nct7715,
> > p3t1750,
> > p3t1755,
> > pct2075,
> > @@ -107,6 +108,15 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
> > #define LM75_REG_MAX 0x03
> > #define PCT2075_REG_IDLE 0x04
> >
> > +#define NCT7715_CONFIG_RESOLUTION_12_BIT GENMASK(14, 13)
> > +#define NCT7715_CONFIG_SHUTDOWN BIT(8)
> > +#define NCT7715_CONFIG_CONVERSION_RATE_MASK GENMASK(7, 6)
> > +#define NCT7715_CONFIG_EXTENDED_MODE BIT(4)
> > +#define NCT7715_CONFIG_RATE_0_25HZ 0
> > +#define NCT7715_CONFIG_RATE_1HZ BIT(6)
> > +#define NCT7715_CONFIG_RATE_4HZ BIT(7)
> > +#define NCT7715_CONFIG_RATE_8HZ GENMASK(7, 6)
> > +
> > struct lm75_data {
> > const char *label;
> > struct regmap *regmap;
> > @@ -122,6 +132,10 @@ struct lm75_data {
> > /*-----------------------------------------------------------------------*/
> >
> > static const u8 lm75_sample_set_masks[] = { 0 << 5, 1 << 5, 2 << 5, 3 << 5 };
> > +static const u16 nct7715_sample_set_masks[] = {
> > + NCT7715_CONFIG_RATE_8HZ, NCT7715_CONFIG_RATE_4HZ,
> > + NCT7715_CONFIG_RATE_1HZ, NCT7715_CONFIG_RATE_0_25HZ
> > +};
> >
> > #define LM75_ALERT_POLARITY_HIGH_8_BIT (BIT(2))
> > #define LM75_ALERT_POLARITY_HIGH_16_BIT (BIT(2) << 8)
> > @@ -259,6 +273,15 @@ static const struct lm75_params device_params[] = {
> > .sample_times = (unsigned int []){ 30, 60, 120, 240 },
> > .resolutions = (u8 []) {9, 10, 11, 12 },
> > },
> > + [nct7715] = {
> > + .config_reg_16bits = true,
> > + .set_mask = NCT7715_CONFIG_RESOLUTION_12_BIT,
> > + .clr_mask = NCT7715_CONFIG_EXTENDED_MODE,
> > + .default_resolution = 12,
> > + .default_sample_time = 250,
> > + .num_sample_times = 4,
> > + .sample_times = (unsigned int []){ 125, 250, 1000, 4000 },
> > + },
> > [tmp100] = {
> > .set_mask = 3 << 5, /* 12-bit mode */
> > .clr_mask = 1 << 7, /* not one-shot mode */
> > @@ -354,6 +377,11 @@ static inline long lm75_reg_to_mc(s16 temp, u8 resolution)
> > static inline int lm75_write_config(struct lm75_data *data, u16 set_mask,
> > u16 clr_mask)
> > {
> > + if (data->kind == nct7715)
> > + return regmap_update_bits(data->regmap, LM75_REG_CONF,
> > + clr_mask | set_mask | NCT7715_CONFIG_SHUTDOWN,
> > + set_mask);
> > +
> > return regmap_update_bits(data->regmap, LM75_REG_CONF,
> > clr_mask | set_mask | LM75_SHUTDOWN, set_mask);
> > }
> > @@ -486,6 +514,13 @@ static int lm75_update_interval(struct device *dev, long val)
> > if (data->params->resolutions)
> > data->resolution = data->params->resolutions[index];
> > break;
> > + case nct7715:
> > + err = lm75_write_config(data, nct7715_sample_set_masks[index],
> > + NCT7715_CONFIG_CONVERSION_RATE_MASK);
> > + if (err)
> > + return err;
> > + data->sample_time = data->params->sample_times[index];
> > + break;
> > case tmp112:
> > case as6200:
> > err = regmap_update_bits(data->regmap, LM75_REG_CONF,
> > @@ -609,6 +644,8 @@ static int lm75_i2c_reg_read(void *context, unsigned int reg, unsigned int *val)
> > if (reg == LM75_REG_CONF) {
> > if (!data->params->config_reg_16bits)
> > ret = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
> > + else if (data->kind == nct7715)
> > + ret = i2c_smbus_read_word_swapped(client, LM75_REG_CONF);
> > else
> > ret = i2c_smbus_read_word_data(client, LM75_REG_CONF);
> > } else {
> > @@ -628,8 +665,11 @@ static int lm75_i2c_reg_write(void *context, unsigned int reg, unsigned int val)
> > if (reg == PCT2075_REG_IDLE ||
> > (reg == LM75_REG_CONF && !data->params->config_reg_16bits))
> > return i2c_smbus_write_byte_data(client, reg, val);
> > - else if (reg == LM75_REG_CONF)
> > + else if (reg == LM75_REG_CONF) {
> > + if (data->kind == nct7715)
> > + return i2c_smbus_write_word_swapped(client, reg, val);
>
> This code is double swapping. The calling code swaps (bit settings),
> regmap calls this function, where the word is swapped again.
>
> Guenter
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v1] hwmon: (lm75) Add support for Nuvoton NCT7715
2026-09-09 7:10 ` Sheng-Yuan Huang
@ 2026-09-09 14:02 ` Guenter Roeck
2026-09-10 7:16 ` Sheng-Yuan Huang
0 siblings, 1 reply; 5+ messages in thread
From: Guenter Roeck @ 2026-09-09 14:02 UTC (permalink / raw)
To: Sheng-Yuan Huang, linux-hwmon
Cc: Sheng-Yuan Huang, Rob Herring, Krzysztof Kozlowski, Conor Dooley,
Jonathan Corbet, Shuah Khan, Jean Delvare, devicetree,
linux-kernel, linux-doc
On 9/9/26 00:10, Sheng-Yuan Huang wrote:
> Thank you for the review. I may have misunderstood which conversion
> you are referring to, so I would like to clarify both parts.
>
> If this refers to the NCT7715_CONFIG_* masks, they use the logical bit
> positions of the 16-bit configuration register defined by the
> NCT7715 specification. They are not pre-swapped for the SMBus word
> byte order.
>
> If this refers to the I2C accessors, the NCT7715 transfers its 16-bit
> configuration register MSB first. The lm75 regmap bus uses
> reg_read/reg_write callbacks. In this path, regmap passes the logical
> register value to the callbacks, and i2c_smbus_*_word_swapped()
> performs the conversion between that value and the SMBus word byte
> order.
>
> I verified this on hardware by changing update_interval. i2cget shows
> 0xe060, 0xa060, 0x6060, and 0x2060 for 125, 250, 1000, and 4000 ms,
> respectively. After accounting for the SMBus word byte order, these
> are logical values 0x60e0, 0x60a0, 0x6060, and 0x6020. In each case,
> only the NCT7715 conversion-rate field, bits [7:6], is changed.
>
Sure, it works, because your code converts the bytes twice, as I said.
That doesn't make those conversions necessary.
Other chips also use 16-bit config registers. Just use the same approach.
Also, please do not top-post.
Thanks,
Guenter
> Guenter Roeck <linux@roeck-us.net> 於 2026年9月7日週一 下午11:30寫道：
>>
>> On 9/7/26 01:08, hsyemail2@gmail.com wrote:
>>> From: Sheng-Yuan Huang <syhuang3@nuvoton.com>
>>>
>>> The Nuvoton NCT7715 is compatible with the LM75 temperature and
>>> limit register layout, but its 16-bit configuration register is
>>> transmitted most-significant byte first. Add support for the NCT7715,
>>> including byte-swapped SMBus accesses for its configuration register.
>>>
>>> Handle its conversion-rate field and shutdown bit separately, since
>>> their bit positions differ from the standard LM75 layout.
>>>
>> I don't think so. See below.
>>
>>> Signed-off-by: Sheng-Yuan Huang <syhuang3@nuvoton.com>
>>> ---
>>> .../devicetree/bindings/hwmon/lm75.yaml | 1 +
>>> Documentation/hwmon/lm75.rst | 6 ++
>>> drivers/hwmon/lm75.c | 57 ++++++++++++++++++-
>>> 3 files changed, 62 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/hwmon/lm75.yaml b/Documentation/devicetree/bindings/hwmon/lm75.yaml
>>> index b48bf3fd721f..832a8c5d83e9 100644
>>> --- a/Documentation/devicetree/bindings/hwmon/lm75.yaml
>>> +++ b/Documentation/devicetree/bindings/hwmon/lm75.yaml
>>> @@ -31,6 +31,7 @@ properties:
>>> - nxp,p3t1750
>>> - nxp,p3t1755
>>> - nxp,pct2075
>>> + - nuvoton,nct7715
>>> - st,stds75
>>> - st,stlm75
>>> - microchip,tcn75
>>> diff --git a/Documentation/hwmon/lm75.rst b/Documentation/hwmon/lm75.rst
>>> index ca46754e028b..fac0b8f29ddc 100644
>>> --- a/Documentation/hwmon/lm75.rst
>>> +++ b/Documentation/hwmon/lm75.rst
>>> @@ -150,6 +150,12 @@ Supported chips:
>>>
>>> https://ams.com/documents/20143/36005/AS6200_DS000449_4-00.pdf
>>>
>>> + * Nuvoton NCT7715
>>> +
>>> + Prefix: 'nct7715'
>>> +
>>> + Addresses scanned: none
>>> +
>>> Author: Frodo Looijaard <frodol@dds.nl>
>>>
>>> Description
>>> diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
>>> index 2d2d752aeac9..0b55f6b7c68d 100644
>>> --- a/drivers/hwmon/lm75.c
>>> +++ b/drivers/hwmon/lm75.c
>>> @@ -39,6 +39,7 @@ enum lm75_type { /* keep sorted in alphabetical order */
>>> max6626,
>>> max31725,
>>> mcp980x,
>>> + nct7715,
>>> p3t1750,
>>> p3t1755,
>>> pct2075,
>>> @@ -107,6 +108,15 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
>>> #define LM75_REG_MAX 0x03
>>> #define PCT2075_REG_IDLE 0x04
>>>
>>> +#define NCT7715_CONFIG_RESOLUTION_12_BIT GENMASK(14, 13)
>>> +#define NCT7715_CONFIG_SHUTDOWN BIT(8)
>>> +#define NCT7715_CONFIG_CONVERSION_RATE_MASK GENMASK(7, 6)
>>> +#define NCT7715_CONFIG_EXTENDED_MODE BIT(4)
>>> +#define NCT7715_CONFIG_RATE_0_25HZ 0
>>> +#define NCT7715_CONFIG_RATE_1HZ BIT(6)
>>> +#define NCT7715_CONFIG_RATE_4HZ BIT(7)
>>> +#define NCT7715_CONFIG_RATE_8HZ GENMASK(7, 6)
>>> +
>>> struct lm75_data {
>>> const char *label;
>>> struct regmap *regmap;
>>> @@ -122,6 +132,10 @@ struct lm75_data {
>>> /*-----------------------------------------------------------------------*/
>>>
>>> static const u8 lm75_sample_set_masks[] = { 0 << 5, 1 << 5, 2 << 5, 3 << 5 };
>>> +static const u16 nct7715_sample_set_masks[] = {
>>> + NCT7715_CONFIG_RATE_8HZ, NCT7715_CONFIG_RATE_4HZ,
>>> + NCT7715_CONFIG_RATE_1HZ, NCT7715_CONFIG_RATE_0_25HZ
>>> +};
>>>
>>> #define LM75_ALERT_POLARITY_HIGH_8_BIT (BIT(2))
>>> #define LM75_ALERT_POLARITY_HIGH_16_BIT (BIT(2) << 8)
>>> @@ -259,6 +273,15 @@ static const struct lm75_params device_params[] = {
>>> .sample_times = (unsigned int []){ 30, 60, 120, 240 },
>>> .resolutions = (u8 []) {9, 10, 11, 12 },
>>> },
>>> + [nct7715] = {
>>> + .config_reg_16bits = true,
>>> + .set_mask = NCT7715_CONFIG_RESOLUTION_12_BIT,
>>> + .clr_mask = NCT7715_CONFIG_EXTENDED_MODE,
>>> + .default_resolution = 12,
>>> + .default_sample_time = 250,
>>> + .num_sample_times = 4,
>>> + .sample_times = (unsigned int []){ 125, 250, 1000, 4000 },
>>> + },
>>> [tmp100] = {
>>> .set_mask = 3 << 5, /* 12-bit mode */
>>> .clr_mask = 1 << 7, /* not one-shot mode */
>>> @@ -354,6 +377,11 @@ static inline long lm75_reg_to_mc(s16 temp, u8 resolution)
>>> static inline int lm75_write_config(struct lm75_data *data, u16 set_mask,
>>> u16 clr_mask)
>>> {
>>> + if (data->kind == nct7715)
>>> + return regmap_update_bits(data->regmap, LM75_REG_CONF,
>>> + clr_mask | set_mask | NCT7715_CONFIG_SHUTDOWN,
>>> + set_mask);
>>> +
>>> return regmap_update_bits(data->regmap, LM75_REG_CONF,
>>> clr_mask | set_mask | LM75_SHUTDOWN, set_mask);
>>> }
>>> @@ -486,6 +514,13 @@ static int lm75_update_interval(struct device *dev, long val)
>>> if (data->params->resolutions)
>>> data->resolution = data->params->resolutions[index];
>>> break;
>>> + case nct7715:
>>> + err = lm75_write_config(data, nct7715_sample_set_masks[index],
>>> + NCT7715_CONFIG_CONVERSION_RATE_MASK);
>>> + if (err)
>>> + return err;
>>> + data->sample_time = data->params->sample_times[index];
>>> + break;
>>> case tmp112:
>>> case as6200:
>>> err = regmap_update_bits(data->regmap, LM75_REG_CONF,
>>> @@ -609,6 +644,8 @@ static int lm75_i2c_reg_read(void *context, unsigned int reg, unsigned int *val)
>>> if (reg == LM75_REG_CONF) {
>>> if (!data->params->config_reg_16bits)
>>> ret = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
>>> + else if (data->kind == nct7715)
>>> + ret = i2c_smbus_read_word_swapped(client, LM75_REG_CONF);
>>> else
>>> ret = i2c_smbus_read_word_data(client, LM75_REG_CONF);
>>> } else {
>>> @@ -628,8 +665,11 @@ static int lm75_i2c_reg_write(void *context, unsigned int reg, unsigned int val)
>>> if (reg == PCT2075_REG_IDLE ||
>>> (reg == LM75_REG_CONF && !data->params->config_reg_16bits))
>>> return i2c_smbus_write_byte_data(client, reg, val);
>>> - else if (reg == LM75_REG_CONF)
>>> + else if (reg == LM75_REG_CONF) {
>>> + if (data->kind == nct7715)
>>> + return i2c_smbus_write_word_swapped(client, reg, val);
>>
>> This code is double swapping. The calling code swaps (bit settings),
>> regmap calls this function, where the word is swapped again.
>>
>> Guenter
>>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v1] hwmon: (lm75) Add support for Nuvoton NCT7715
2026-09-09 14:02 ` Guenter Roeck
@ 2026-09-10 7:16 ` Sheng-Yuan Huang
0 siblings, 0 replies; 5+ messages in thread
From: Sheng-Yuan Huang @ 2026-09-10 7:16 UTC (permalink / raw)
To: Guenter Roeck
Cc: linux-hwmon, Sheng-Yuan Huang, Rob Herring, Krzysztof Kozlowski,
Conor Dooley, Jonathan Corbet, Shuah Khan, Jean Delvare,
devicetree, linux-kernel, linux-doc
On Wed, Sep 09, 2026 at 10:02 PM, Guenter Roeck <linux@roeck-us.net> wrote:
>
> Sure, it works, because your code converts the bytes twice, as I said.
> That doesn't make those conversions necessary.
>
> Other chips also use 16-bit config registers. Just use the same approach.
>
Thank you for the detailed guidance and clarification.
I think I understand it now, and I will send a v2 patch soon.
Thanks,
Sheng-Yuan
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2026-09-10 7:16 UTC | newest]
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2026-09-07 8:08 [PATCH v1] hwmon: (lm75) Add support for Nuvoton NCT7715 hsyemail2
2026-09-07 15:29 ` Guenter Roeck
2026-09-09 7:10 ` Sheng-Yuan Huang
2026-09-09 14:02 ` Guenter Roeck
2026-09-10 7:16 ` Sheng-Yuan Huang
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