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[linux,hwmon-next,v5,0/3] SB-TSI hwmon driver v5

Message ID 20201211215427.3281681-1-kunyi@google.com
Headers show
Series SB-TSI hwmon driver v5 | expand

Message

Kun Yi Dec. 11, 2020, 9:54 p.m. UTC
v5: addressed comments in v4
v4: addressed comments in v3; converted DT binding to required schema
v3: addressed comment in v2 and improved documentation
v2: rewrote using devm_hwmon_device_register_with_info() API and addressed
    comments received in v1
v1: first version

Kun Yi (3):
  hwmon: (sbtsi) Add basic support for SB-TSI sensors
  hwmon: (sbtsi) Add documentation
  dt-bindings: (hwmon/sbtsi_tmep) Add SB-TSI hwmon driver bindings

 .../devicetree/bindings/hwmon/amd,sbtsi.yaml  |  54 ++++
 Documentation/hwmon/index.rst                 |   1 +
 Documentation/hwmon/sbtsi_temp.rst            |  40 +++
 drivers/hwmon/Kconfig                         |  10 +
 drivers/hwmon/Makefile                        |   1 +
 drivers/hwmon/sbtsi_temp.c                    | 250 ++++++++++++++++++
 6 files changed, 356 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
 create mode 100644 Documentation/hwmon/sbtsi_temp.rst
 create mode 100644 drivers/hwmon/sbtsi_temp.c

Comments

Guenter Roeck Dec. 12, 2020, 4:44 p.m. UTC | #1
On Fri, Dec 11, 2020 at 01:54:25PM -0800, Kun Yi wrote:
> SB Temperature Sensor Interface (SB-TSI) is an SMBus compatible

> interface that reports AMD SoC's Ttcl (normalized temperature),

> and resembles a typical 8-pin remote temperature sensor's I2C interface

> to BMC.

> 

> This commit adds basic support using this interface to read CPU

> temperature, and read/write high/low CPU temp thresholds.

> 

> To instantiate this driver on an AMD CPU with SB-TSI

> support, the i2c bus number would be the bus connected from the board

> management controller (BMC) to the CPU. The i2c address is specified in

> Section 6.3.1 of the spec [1]: The SB-TSI address is normally 98h for

> socket 0 and 90h for socket 1, but it could vary based on hardware address

> select pins.

> 

> [1]: https://www.amd.com/system/files/TechDocs/56255_OSRR.pdf

> 

> Test status: tested reading temp1_input, and reading/writing

> temp1_max/min.

> 

> Signed-off-by: Kun Yi <kunyi@google.com>


Applied.

Thanks,
Guenter

> ---

>  drivers/hwmon/Kconfig      |  10 ++

>  drivers/hwmon/Makefile     |   1 +

>  drivers/hwmon/sbtsi_temp.c | 250 +++++++++++++++++++++++++++++++++++++

>  3 files changed, 261 insertions(+)

>  create mode 100644 drivers/hwmon/sbtsi_temp.c

> 

> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig

> index 3c059fc23cd6..3d6a809700ae 100644

> --- a/drivers/hwmon/Kconfig

> +++ b/drivers/hwmon/Kconfig

> @@ -1522,6 +1522,16 @@ config SENSORS_SL28CPLD

>  	  This driver can also be built as a module.  If so, the module

>  	  will be called sl28cpld-hwmon.

>  

> +config SENSORS_SBTSI

> +	tristate "Emulated SB-TSI temperature sensor"

> +	depends on I2C

> +	help

> +	  If you say yes here you get support for emulated temperature

> +	  sensors on AMD SoCs with SB-TSI interface connected to a BMC device.

> +

> +	  This driver can also be built as a module. If so, the module will

> +	  be called sbtsi_temp.

> +

>  config SENSORS_SHT15

>  	tristate "Sensiron humidity and temperature sensors. SHT15 and compat."

>  	depends on GPIOLIB || COMPILE_TEST

> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile

> index 01ca5d3fbad4..ee8c037919da 100644

> --- a/drivers/hwmon/Makefile

> +++ b/drivers/hwmon/Makefile

> @@ -160,6 +160,7 @@ obj-$(CONFIG_SENSORS_POWR1220)  += powr1220.o

>  obj-$(CONFIG_SENSORS_PWM_FAN)	+= pwm-fan.o

>  obj-$(CONFIG_SENSORS_RASPBERRYPI_HWMON)	+= raspberrypi-hwmon.o

>  obj-$(CONFIG_SENSORS_S3C)	+= s3c-hwmon.o

> +obj-$(CONFIG_SENSORS_SBTSI)	+= sbtsi_temp.o

>  obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o

>  obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o

>  obj-$(CONFIG_SENSORS_SCH5636)	+= sch5636.o

> diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c

> new file mode 100644

> index 000000000000..e35357c48b8e

> --- /dev/null

> +++ b/drivers/hwmon/sbtsi_temp.c

> @@ -0,0 +1,250 @@

> +// SPDX-License-Identifier: GPL-2.0-or-later

> +/*

> + * sbtsi_temp.c - hwmon driver for a SBI Temperature Sensor Interface (SB-TSI)

> + *                compliant AMD SoC temperature device.

> + *

> + * Copyright (c) 2020, Google Inc.

> + * Copyright (c) 2020, Kun Yi <kunyi@google.com>

> + */

> +

> +#include <linux/err.h>

> +#include <linux/i2c.h>

> +#include <linux/init.h>

> +#include <linux/hwmon.h>

> +#include <linux/module.h>

> +#include <linux/mutex.h>

> +#include <linux/of_device.h>

> +#include <linux/of.h>

> +

> +/*

> + * SB-TSI registers only support SMBus byte data access. "_INT" registers are

> + * the integer part of a temperature value or limit, and "_DEC" registers are

> + * corresponding decimal parts.

> + */

> +#define SBTSI_REG_TEMP_INT		0x01 /* RO */

> +#define SBTSI_REG_STATUS		0x02 /* RO */

> +#define SBTSI_REG_CONFIG		0x03 /* RO */

> +#define SBTSI_REG_TEMP_HIGH_INT		0x07 /* RW */

> +#define SBTSI_REG_TEMP_LOW_INT		0x08 /* RW */

> +#define SBTSI_REG_TEMP_DEC		0x10 /* RW */

> +#define SBTSI_REG_TEMP_HIGH_DEC		0x13 /* RW */

> +#define SBTSI_REG_TEMP_LOW_DEC		0x14 /* RW */

> +

> +#define SBTSI_CONFIG_READ_ORDER_SHIFT	5

> +

> +#define SBTSI_TEMP_MIN	0

> +#define SBTSI_TEMP_MAX	255875

> +

> +/* Each client has this additional data */

> +struct sbtsi_data {

> +	struct i2c_client *client;

> +	struct mutex lock;

> +};

> +

> +/*

> + * From SB-TSI spec: CPU temperature readings and limit registers encode the

> + * temperature in increments of 0.125 from 0 to 255.875. The "high byte"

> + * register encodes the base-2 of the integer portion, and the upper 3 bits of

> + * the "low byte" encode in base-2 the decimal portion.

> + *

> + * e.g. INT=0x19, DEC=0x20 represents 25.125 degrees Celsius

> + *

> + * Therefore temperature in millidegree Celsius =

> + *   (INT + DEC / 256) * 1000 = (INT * 8 + DEC / 32) * 125

> + */

> +static inline int sbtsi_reg_to_mc(s32 integer, s32 decimal)

> +{

> +	return ((integer << 3) + (decimal >> 5)) * 125;

> +}

> +

> +/*

> + * Inversely, given temperature in millidegree Celsius

> + *   INT = (TEMP / 125) / 8

> + *   DEC = ((TEMP / 125) % 8) * 32

> + * Caller have to make sure temp doesn't exceed 255875, the max valid value.

> + */

> +static inline void sbtsi_mc_to_reg(s32 temp, u8 *integer, u8 *decimal)

> +{

> +	temp /= 125;

> +	*integer = temp >> 3;

> +	*decimal = (temp & 0x7) << 5;

> +}

> +

> +static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,

> +		      u32 attr, int channel, long *val)

> +{

> +	struct sbtsi_data *data = dev_get_drvdata(dev);

> +	s32 temp_int, temp_dec;

> +	int err;

> +

> +	switch (attr) {

> +	case hwmon_temp_input:

> +		/*

> +		 * ReadOrder bit specifies the reading order of integer and

> +		 * decimal part of CPU temp for atomic reads. If bit == 0,

> +		 * reading integer part triggers latching of the decimal part,

> +		 * so integer part should be read first. If bit == 1, read

> +		 * order should be reversed.

> +		 */

> +		err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);

> +		if (err < 0)

> +			return err;

> +

> +		mutex_lock(&data->lock);

> +		if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {

> +			temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);

> +			temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);

> +		} else {

> +			temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);

> +			temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);

> +		}

> +		mutex_unlock(&data->lock);

> +		break;

> +	case hwmon_temp_max:

> +		mutex_lock(&data->lock);

> +		temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);

> +		temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);

> +		mutex_unlock(&data->lock);

> +		break;

> +	case hwmon_temp_min:

> +		mutex_lock(&data->lock);

> +		temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);

> +		temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);

> +		mutex_unlock(&data->lock);

> +		break;

> +	default:

> +		return -EINVAL;

> +	}

> +

> +

> +	if (temp_int < 0)

> +		return temp_int;

> +	if (temp_dec < 0)

> +		return temp_dec;

> +

> +	*val = sbtsi_reg_to_mc(temp_int, temp_dec);

> +

> +	return 0;

> +}

> +

> +static int sbtsi_write(struct device *dev, enum hwmon_sensor_types type,

> +		       u32 attr, int channel, long val)

> +{

> +	struct sbtsi_data *data = dev_get_drvdata(dev);

> +	int reg_int, reg_dec, err;

> +	u8 temp_int, temp_dec;

> +

> +	switch (attr) {

> +	case hwmon_temp_max:

> +		reg_int = SBTSI_REG_TEMP_HIGH_INT;

> +		reg_dec = SBTSI_REG_TEMP_HIGH_DEC;

> +		break;

> +	case hwmon_temp_min:

> +		reg_int = SBTSI_REG_TEMP_LOW_INT;

> +		reg_dec = SBTSI_REG_TEMP_LOW_DEC;

> +		break;

> +	default:

> +		return -EINVAL;

> +	}

> +

> +	val = clamp_val(val, SBTSI_TEMP_MIN, SBTSI_TEMP_MAX);

> +	sbtsi_mc_to_reg(val, &temp_int, &temp_dec);

> +

> +	mutex_lock(&data->lock);

> +	err = i2c_smbus_write_byte_data(data->client, reg_int, temp_int);

> +	if (err)

> +		goto exit;

> +

> +	err = i2c_smbus_write_byte_data(data->client, reg_dec, temp_dec);

> +exit:

> +	mutex_unlock(&data->lock);

> +	return err;

> +}

> +

> +static umode_t sbtsi_is_visible(const void *data,

> +				enum hwmon_sensor_types type,

> +				u32 attr, int channel)

> +{

> +	switch (type) {

> +	case hwmon_temp:

> +		switch (attr) {

> +		case hwmon_temp_input:

> +			return 0444;

> +		case hwmon_temp_min:

> +			return 0644;

> +		case hwmon_temp_max:

> +			return 0644;

> +		}

> +		break;

> +	default:

> +		break;

> +	}

> +	return 0;

> +}

> +

> +static const struct hwmon_channel_info *sbtsi_info[] = {

> +	HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),

> +	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX),

> +	NULL

> +};

> +

> +static const struct hwmon_ops sbtsi_hwmon_ops = {

> +	.is_visible = sbtsi_is_visible,

> +	.read = sbtsi_read,

> +	.write = sbtsi_write,

> +};

> +

> +static const struct hwmon_chip_info sbtsi_chip_info = {

> +	.ops = &sbtsi_hwmon_ops,

> +	.info = sbtsi_info,

> +};

> +

> +static int sbtsi_probe(struct i2c_client *client,

> +		       const struct i2c_device_id *id)

> +{

> +	struct device *dev = &client->dev;

> +	struct device *hwmon_dev;

> +	struct sbtsi_data *data;

> +

> +	data = devm_kzalloc(dev, sizeof(struct sbtsi_data), GFP_KERNEL);

> +	if (!data)

> +		return -ENOMEM;

> +

> +	data->client = client;

> +	mutex_init(&data->lock);

> +

> +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data, &sbtsi_chip_info,

> +							 NULL);

> +

> +	return PTR_ERR_OR_ZERO(hwmon_dev);

> +}

> +

> +static const struct i2c_device_id sbtsi_id[] = {

> +	{"sbtsi", 0},

> +	{}

> +};

> +MODULE_DEVICE_TABLE(i2c, sbtsi_id);

> +

> +static const struct of_device_id __maybe_unused sbtsi_of_match[] = {

> +	{

> +		.compatible = "amd,sbtsi",

> +	},

> +	{ },

> +};

> +MODULE_DEVICE_TABLE(of, sbtsi_of_match);

> +

> +static struct i2c_driver sbtsi_driver = {

> +	.class = I2C_CLASS_HWMON,

> +	.driver = {

> +		.name = "sbtsi",

> +		.of_match_table = of_match_ptr(sbtsi_of_match),

> +	},

> +	.probe = sbtsi_probe,

> +	.id_table = sbtsi_id,

> +};

> +

> +module_i2c_driver(sbtsi_driver);

> +

> +MODULE_AUTHOR("Kun Yi <kunyi@google.com>");

> +MODULE_DESCRIPTION("Hwmon driver for AMD SB-TSI emulated sensor");

> +MODULE_LICENSE("GPL");
Guenter Roeck Dec. 12, 2020, 4:45 p.m. UTC | #2
On Fri, Dec 11, 2020 at 01:54:26PM -0800, Kun Yi wrote:
> Document the SB-TSI sensor interface driver.

> 

> Signed-off-by: Kun Yi <kunyi@google.com>


Applied. Note that I added the SPDX identifier to match
the one used in the source file.

Guenter

> ---

>  Documentation/hwmon/index.rst      |  1 +

>  Documentation/hwmon/sbtsi_temp.rst | 40 ++++++++++++++++++++++++++++++

>  2 files changed, 41 insertions(+)

>  create mode 100644 Documentation/hwmon/sbtsi_temp.rst

> 

> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst

> index fd6fae46b99c..509fb3bcafb2 100644

> --- a/Documentation/hwmon/index.rst

> +++ b/Documentation/hwmon/index.rst

> @@ -151,6 +151,7 @@ Hardware Monitoring Kernel Drivers

>     pxe1610

>     pwm-fan

>     raspberrypi-hwmon

> +   sbtsi_temp

>     sch5627

>     sch5636

>     scpi-hwmon

> diff --git a/Documentation/hwmon/sbtsi_temp.rst b/Documentation/hwmon/sbtsi_temp.rst

> new file mode 100644

> index 000000000000..9f0f197c8aa2

> --- /dev/null

> +++ b/Documentation/hwmon/sbtsi_temp.rst

> @@ -0,0 +1,40 @@

> +Kernel driver sbtsi_temp

> +==================

> +

> +Supported hardware:

> +

> +  * Sideband interface (SBI) Temperature Sensor Interface (SB-TSI)

> +    compliant AMD SoC temperature device.

> +

> +    Prefix: 'sbtsi_temp'

> +

> +    Addresses scanned: This driver doesn't support address scanning.

> +

> +    To instantiate this driver on an AMD CPU with SB-TSI

> +    support, the i2c bus number would be the bus connected from the board

> +    management controller (BMC) to the CPU. The i2c address is specified in

> +    Section 6.3.1 of the SoC register reference: The SB-TSI address is normally

> +    98h for socket 0 and 90h for socket 1, but it could vary based on hardware

> +    address select pins.

> +

> +    Datasheet: The SB-TSI interface and protocol is available as part of

> +               the open source SoC register reference at:

> +

> +	       https://www.amd.com/system/files/TechDocs/56255_OSRR.pdf

> +

> +               The Advanced Platform Management Link (APML) Specification is

> +               available at:

> +

> +	       http://developer.amd.com/wordpress/media/2012/10/41918.pdf

> +

> +Author: Kun Yi <kunyi@google.com>

> +

> +Description

> +-----------

> +

> +The SBI temperature sensor interface (SB-TSI) is an emulation of the software

> +and physical interface of a typical 8-pin remote temperature sensor (RTS) on

> +AMD SoCs. It implements one temperature sensor with readings and limit

> +registers encode the temperature in increments of 0.125 from 0 to 255.875.

> +Limits can be set through the writable thresholds, and if reached will trigger

> +corresponding alert signals.
Kun Yi Dec. 14, 2020, 5:59 p.m. UTC | #3
On Sat, Dec 12, 2020 at 8:44 AM Guenter Roeck <linux@roeck-us.net> wrote:
>

> On Fri, Dec 11, 2020 at 01:54:25PM -0800, Kun Yi wrote:

> > SB Temperature Sensor Interface (SB-TSI) is an SMBus compatible

> > interface that reports AMD SoC's Ttcl (normalized temperature),

> > and resembles a typical 8-pin remote temperature sensor's I2C interface

> > to BMC.

> >

> > This commit adds basic support using this interface to read CPU

> > temperature, and read/write high/low CPU temp thresholds.

> >

> > To instantiate this driver on an AMD CPU with SB-TSI

> > support, the i2c bus number would be the bus connected from the board

> > management controller (BMC) to the CPU. The i2c address is specified in

> > Section 6.3.1 of the spec [1]: The SB-TSI address is normally 98h for

> > socket 0 and 90h for socket 1, but it could vary based on hardware address

> > select pins.

> >

> > [1]: https://www.amd.com/system/files/TechDocs/56255_OSRR.pdf

> >

> > Test status: tested reading temp1_input, and reading/writing

> > temp1_max/min.

> >

> > Signed-off-by: Kun Yi <kunyi@google.com>

>

> Applied.

>

> Thanks,

> Guenter


Many thanks!

Kun
>

> > ---

> >  drivers/hwmon/Kconfig      |  10 ++

> >  drivers/hwmon/Makefile     |   1 +

> >  drivers/hwmon/sbtsi_temp.c | 250 +++++++++++++++++++++++++++++++++++++

> >  3 files changed, 261 insertions(+)

> >  create mode 100644 drivers/hwmon/sbtsi_temp.c

> >

> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig

> > index 3c059fc23cd6..3d6a809700ae 100644

> > --- a/drivers/hwmon/Kconfig

> > +++ b/drivers/hwmon/Kconfig

> > @@ -1522,6 +1522,16 @@ config SENSORS_SL28CPLD

> >         This driver can also be built as a module.  If so, the module

> >         will be called sl28cpld-hwmon.

> >

> > +config SENSORS_SBTSI

> > +     tristate "Emulated SB-TSI temperature sensor"

> > +     depends on I2C

> > +     help

> > +       If you say yes here you get support for emulated temperature

> > +       sensors on AMD SoCs with SB-TSI interface connected to a BMC device.

> > +

> > +       This driver can also be built as a module. If so, the module will

> > +       be called sbtsi_temp.

> > +

> >  config SENSORS_SHT15

> >       tristate "Sensiron humidity and temperature sensors. SHT15 and compat."

> >       depends on GPIOLIB || COMPILE_TEST

> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile

> > index 01ca5d3fbad4..ee8c037919da 100644

> > --- a/drivers/hwmon/Makefile

> > +++ b/drivers/hwmon/Makefile

> > @@ -160,6 +160,7 @@ obj-$(CONFIG_SENSORS_POWR1220)  += powr1220.o

> >  obj-$(CONFIG_SENSORS_PWM_FAN)        += pwm-fan.o

> >  obj-$(CONFIG_SENSORS_RASPBERRYPI_HWMON)      += raspberrypi-hwmon.o

> >  obj-$(CONFIG_SENSORS_S3C)    += s3c-hwmon.o

> > +obj-$(CONFIG_SENSORS_SBTSI)  += sbtsi_temp.o

> >  obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o

> >  obj-$(CONFIG_SENSORS_SCH5627)        += sch5627.o

> >  obj-$(CONFIG_SENSORS_SCH5636)        += sch5636.o

> > diff --git a/drivers/hwmon/sbtsi_temp.c b/drivers/hwmon/sbtsi_temp.c

> > new file mode 100644

> > index 000000000000..e35357c48b8e

> > --- /dev/null

> > +++ b/drivers/hwmon/sbtsi_temp.c

> > @@ -0,0 +1,250 @@

> > +// SPDX-License-Identifier: GPL-2.0-or-later

> > +/*

> > + * sbtsi_temp.c - hwmon driver for a SBI Temperature Sensor Interface (SB-TSI)

> > + *                compliant AMD SoC temperature device.

> > + *

> > + * Copyright (c) 2020, Google Inc.

> > + * Copyright (c) 2020, Kun Yi <kunyi@google.com>

> > + */

> > +

> > +#include <linux/err.h>

> > +#include <linux/i2c.h>

> > +#include <linux/init.h>

> > +#include <linux/hwmon.h>

> > +#include <linux/module.h>

> > +#include <linux/mutex.h>

> > +#include <linux/of_device.h>

> > +#include <linux/of.h>

> > +

> > +/*

> > + * SB-TSI registers only support SMBus byte data access. "_INT" registers are

> > + * the integer part of a temperature value or limit, and "_DEC" registers are

> > + * corresponding decimal parts.

> > + */

> > +#define SBTSI_REG_TEMP_INT           0x01 /* RO */

> > +#define SBTSI_REG_STATUS             0x02 /* RO */

> > +#define SBTSI_REG_CONFIG             0x03 /* RO */

> > +#define SBTSI_REG_TEMP_HIGH_INT              0x07 /* RW */

> > +#define SBTSI_REG_TEMP_LOW_INT               0x08 /* RW */

> > +#define SBTSI_REG_TEMP_DEC           0x10 /* RW */

> > +#define SBTSI_REG_TEMP_HIGH_DEC              0x13 /* RW */

> > +#define SBTSI_REG_TEMP_LOW_DEC               0x14 /* RW */

> > +

> > +#define SBTSI_CONFIG_READ_ORDER_SHIFT        5

> > +

> > +#define SBTSI_TEMP_MIN       0

> > +#define SBTSI_TEMP_MAX       255875

> > +

> > +/* Each client has this additional data */

> > +struct sbtsi_data {

> > +     struct i2c_client *client;

> > +     struct mutex lock;

> > +};

> > +

> > +/*

> > + * From SB-TSI spec: CPU temperature readings and limit registers encode the

> > + * temperature in increments of 0.125 from 0 to 255.875. The "high byte"

> > + * register encodes the base-2 of the integer portion, and the upper 3 bits of

> > + * the "low byte" encode in base-2 the decimal portion.

> > + *

> > + * e.g. INT=0x19, DEC=0x20 represents 25.125 degrees Celsius

> > + *

> > + * Therefore temperature in millidegree Celsius =

> > + *   (INT + DEC / 256) * 1000 = (INT * 8 + DEC / 32) * 125

> > + */

> > +static inline int sbtsi_reg_to_mc(s32 integer, s32 decimal)

> > +{

> > +     return ((integer << 3) + (decimal >> 5)) * 125;

> > +}

> > +

> > +/*

> > + * Inversely, given temperature in millidegree Celsius

> > + *   INT = (TEMP / 125) / 8

> > + *   DEC = ((TEMP / 125) % 8) * 32

> > + * Caller have to make sure temp doesn't exceed 255875, the max valid value.

> > + */

> > +static inline void sbtsi_mc_to_reg(s32 temp, u8 *integer, u8 *decimal)

> > +{

> > +     temp /= 125;

> > +     *integer = temp >> 3;

> > +     *decimal = (temp & 0x7) << 5;

> > +}

> > +

> > +static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,

> > +                   u32 attr, int channel, long *val)

> > +{

> > +     struct sbtsi_data *data = dev_get_drvdata(dev);

> > +     s32 temp_int, temp_dec;

> > +     int err;

> > +

> > +     switch (attr) {

> > +     case hwmon_temp_input:

> > +             /*

> > +              * ReadOrder bit specifies the reading order of integer and

> > +              * decimal part of CPU temp for atomic reads. If bit == 0,

> > +              * reading integer part triggers latching of the decimal part,

> > +              * so integer part should be read first. If bit == 1, read

> > +              * order should be reversed.

> > +              */

> > +             err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);

> > +             if (err < 0)

> > +                     return err;

> > +

> > +             mutex_lock(&data->lock);

> > +             if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {

> > +                     temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);

> > +                     temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);

> > +             } else {

> > +                     temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);

> > +                     temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);

> > +             }

> > +             mutex_unlock(&data->lock);

> > +             break;

> > +     case hwmon_temp_max:

> > +             mutex_lock(&data->lock);

> > +             temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);

> > +             temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);

> > +             mutex_unlock(&data->lock);

> > +             break;

> > +     case hwmon_temp_min:

> > +             mutex_lock(&data->lock);

> > +             temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);

> > +             temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);

> > +             mutex_unlock(&data->lock);

> > +             break;

> > +     default:

> > +             return -EINVAL;

> > +     }

> > +

> > +

> > +     if (temp_int < 0)

> > +             return temp_int;

> > +     if (temp_dec < 0)

> > +             return temp_dec;

> > +

> > +     *val = sbtsi_reg_to_mc(temp_int, temp_dec);

> > +

> > +     return 0;

> > +}

> > +

> > +static int sbtsi_write(struct device *dev, enum hwmon_sensor_types type,

> > +                    u32 attr, int channel, long val)

> > +{

> > +     struct sbtsi_data *data = dev_get_drvdata(dev);

> > +     int reg_int, reg_dec, err;

> > +     u8 temp_int, temp_dec;

> > +

> > +     switch (attr) {

> > +     case hwmon_temp_max:

> > +             reg_int = SBTSI_REG_TEMP_HIGH_INT;

> > +             reg_dec = SBTSI_REG_TEMP_HIGH_DEC;

> > +             break;

> > +     case hwmon_temp_min:

> > +             reg_int = SBTSI_REG_TEMP_LOW_INT;

> > +             reg_dec = SBTSI_REG_TEMP_LOW_DEC;

> > +             break;

> > +     default:

> > +             return -EINVAL;

> > +     }

> > +

> > +     val = clamp_val(val, SBTSI_TEMP_MIN, SBTSI_TEMP_MAX);

> > +     sbtsi_mc_to_reg(val, &temp_int, &temp_dec);

> > +

> > +     mutex_lock(&data->lock);

> > +     err = i2c_smbus_write_byte_data(data->client, reg_int, temp_int);

> > +     if (err)

> > +             goto exit;

> > +

> > +     err = i2c_smbus_write_byte_data(data->client, reg_dec, temp_dec);

> > +exit:

> > +     mutex_unlock(&data->lock);

> > +     return err;

> > +}

> > +

> > +static umode_t sbtsi_is_visible(const void *data,

> > +                             enum hwmon_sensor_types type,

> > +                             u32 attr, int channel)

> > +{

> > +     switch (type) {

> > +     case hwmon_temp:

> > +             switch (attr) {

> > +             case hwmon_temp_input:

> > +                     return 0444;

> > +             case hwmon_temp_min:

> > +                     return 0644;

> > +             case hwmon_temp_max:

> > +                     return 0644;

> > +             }

> > +             break;

> > +     default:

> > +             break;

> > +     }

> > +     return 0;

> > +}

> > +

> > +static const struct hwmon_channel_info *sbtsi_info[] = {

> > +     HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),

> > +     HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX),

> > +     NULL

> > +};

> > +

> > +static const struct hwmon_ops sbtsi_hwmon_ops = {

> > +     .is_visible = sbtsi_is_visible,

> > +     .read = sbtsi_read,

> > +     .write = sbtsi_write,

> > +};

> > +

> > +static const struct hwmon_chip_info sbtsi_chip_info = {

> > +     .ops = &sbtsi_hwmon_ops,

> > +     .info = sbtsi_info,

> > +};

> > +

> > +static int sbtsi_probe(struct i2c_client *client,

> > +                    const struct i2c_device_id *id)

> > +{

> > +     struct device *dev = &client->dev;

> > +     struct device *hwmon_dev;

> > +     struct sbtsi_data *data;

> > +

> > +     data = devm_kzalloc(dev, sizeof(struct sbtsi_data), GFP_KERNEL);

> > +     if (!data)

> > +             return -ENOMEM;

> > +

> > +     data->client = client;

> > +     mutex_init(&data->lock);

> > +

> > +     hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data, &sbtsi_chip_info,

> > +                                                      NULL);

> > +

> > +     return PTR_ERR_OR_ZERO(hwmon_dev);

> > +}

> > +

> > +static const struct i2c_device_id sbtsi_id[] = {

> > +     {"sbtsi", 0},

> > +     {}

> > +};

> > +MODULE_DEVICE_TABLE(i2c, sbtsi_id);

> > +

> > +static const struct of_device_id __maybe_unused sbtsi_of_match[] = {

> > +     {

> > +             .compatible = "amd,sbtsi",

> > +     },

> > +     { },

> > +};

> > +MODULE_DEVICE_TABLE(of, sbtsi_of_match);

> > +

> > +static struct i2c_driver sbtsi_driver = {

> > +     .class = I2C_CLASS_HWMON,

> > +     .driver = {

> > +             .name = "sbtsi",

> > +             .of_match_table = of_match_ptr(sbtsi_of_match),

> > +     },

> > +     .probe = sbtsi_probe,

> > +     .id_table = sbtsi_id,

> > +};

> > +

> > +module_i2c_driver(sbtsi_driver);

> > +

> > +MODULE_AUTHOR("Kun Yi <kunyi@google.com>");

> > +MODULE_DESCRIPTION("Hwmon driver for AMD SB-TSI emulated sensor");

> > +MODULE_LICENSE("GPL");