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

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

[Kun Yi]

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

-- 
2.29.2.684.gfbc64c5ab5-goog

[PATCH linux hwmon-next v5 1/3] hwmon: (sbtsi) Add basic support for SB-TSI sensors

[Kun Yi]

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>
---
 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");
-- 
2.29.2.684.gfbc64c5ab5-goog

[PATCH linux hwmon-next v5 2/3] hwmon: (sbtsi) Add documentation

[Kun Yi]

Document the SB-TSI sensor interface driver.

Signed-off-by: Kun Yi <kunyi@google.com>
---
 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.
-- 
2.29.2.684.gfbc64c5ab5-goog

[PATCH linux hwmon-next v5 3/3] dt-bindings: (hwmon/sbtsi_tmep) Add SB-TSI hwmon driver bindings

[Kun Yi]

Document device tree bindings for AMD SB-TSI emulated temperature
sensor.

Signed-off-by: Kun Yi <kunyi@google.com>
---
 .../devicetree/bindings/hwmon/amd,sbtsi.yaml  | 54 +++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
new file mode 100644
index 000000000000..446b09f1ce94
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/amd,sbtsi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: >
+  Sideband interface Temperature Sensor Interface (SB-TSI) compliant
+  AMD SoC temperature device
+
+maintainers:
+  - Kun Yi <kunyi@google.com>
+  - Supreeth Venkatesh <supreeth.venkatesh@amd.com>
+
+description: |
+  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. The emulated thermal sensor can report temperatures in increments
+  of 0.125 degrees, ranging from 0 to 255.875.
+
+properties:
+  compatible:
+    enum:
+      - amd,sbtsi
+
+  reg:
+    maxItems: 1
+    description: |
+      I2C bus address of the device as 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.
+      \[open source SoC register reference\]
+        https://www.amd.com/system/files/TechDocs/56255_OSRR.pdf
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c0 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        sbtsi@4c {
+                compatible = "amd,sbtsi";
+                reg = <0x4c>;
+        };
+    };
+...
-- 
2.29.2.684.gfbc64c5ab5-goog

Re: [PATCH linux hwmon-next v5 3/3] dt-bindings: (hwmon/sbtsi_tmep) Add SB-TSI hwmon driver bindings

[Guenter Roeck]

On 12/11/20 1:54 PM, Kun Yi wrote:
> Document device tree bindings for AMD SB-TSI emulated temperature
> sensor.
> 
> Signed-off-by: Kun Yi <kunyi@google.com>

Any reason for dropping Rob's Reviewed-by: tag ?

Guenter

> ---
>  .../devicetree/bindings/hwmon/amd,sbtsi.yaml  | 54 +++++++++++++++++++
>  1 file changed, 54 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> new file mode 100644
> index 000000000000..446b09f1ce94
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> @@ -0,0 +1,54 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/hwmon/amd,sbtsi.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: >
> +  Sideband interface Temperature Sensor Interface (SB-TSI) compliant
> +  AMD SoC temperature device
> +
> +maintainers:
> +  - Kun Yi <kunyi@google.com>
> +  - Supreeth Venkatesh <supreeth.venkatesh@amd.com>
> +
> +description: |
> +  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. The emulated thermal sensor can report temperatures in increments
> +  of 0.125 degrees, ranging from 0 to 255.875.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - amd,sbtsi
> +
> +  reg:
> +    maxItems: 1
> +    description: |
> +      I2C bus address of the device as 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.
> +      \[open source SoC register reference\]
> +        https://www.amd.com/system/files/TechDocs/56255_OSRR.pdf
> +
> +required:
> +  - compatible
> +  - reg
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c0 {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        sbtsi@4c {
> +                compatible = "amd,sbtsi";
> +                reg = <0x4c>;
> +        };
> +    };
> +...
> 

Re: [PATCH linux hwmon-next v5 3/3] dt-bindings: (hwmon/sbtsi_tmep) Add SB-TSI hwmon driver bindings

[Kun Yi]

On Fri, Dec 11, 2020 at 3:51 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 12/11/20 1:54 PM, Kun Yi wrote:
> > Document device tree bindings for AMD SB-TSI emulated temperature
> > sensor.
> >
> > Signed-off-by: Kun Yi <kunyi@google.com>
>
> Any reason for dropping Rob's Reviewed-by: tag ?
>
> Guenter

Sorry that was unintentional.

>
> > ---
> >  .../devicetree/bindings/hwmon/amd,sbtsi.yaml  | 54 +++++++++++++++++++
> >  1 file changed, 54 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> > new file mode 100644
> > index 000000000000..446b09f1ce94
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> > @@ -0,0 +1,54 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/hwmon/amd,sbtsi.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: >
> > +  Sideband interface Temperature Sensor Interface (SB-TSI) compliant
> > +  AMD SoC temperature device
> > +
> > +maintainers:
> > +  - Kun Yi <kunyi@google.com>
> > +  - Supreeth Venkatesh <supreeth.venkatesh@amd.com>
> > +
> > +description: |
> > +  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. The emulated thermal sensor can report temperatures in increments
> > +  of 0.125 degrees, ranging from 0 to 255.875.
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - amd,sbtsi
> > +
> > +  reg:
> > +    maxItems: 1
> > +    description: |
> > +      I2C bus address of the device as 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.
> > +      \[open source SoC register reference\]
> > +        https://www.amd.com/system/files/TechDocs/56255_OSRR.pdf
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    i2c0 {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        sbtsi@4c {
> > +                compatible = "amd,sbtsi";
> > +                reg = <0x4c>;
> > +        };
> > +    };
> > +...
> >
>


-- 
Regards,
Kun

Re: [PATCH linux hwmon-next v5 1/3] hwmon: (sbtsi) Add basic support for SB-TSI sensors

[Guenter Roeck]

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");

Re: [PATCH linux hwmon-next v5 2/3] hwmon: (sbtsi) Add documentation

[Guenter Roeck]

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.

Re: [PATCH linux hwmon-next v5 3/3] dt-bindings: (hwmon/sbtsi_tmep) Add SB-TSI hwmon driver bindings

[Guenter Roeck]

On Fri, Dec 11, 2020 at 01:54:27PM -0800, Kun Yi wrote:
> Document device tree bindings for AMD SB-TSI emulated temperature
> sensor.
> 
> Signed-off-by: Kun Yi <kunyi@google.com>

Applied, after fixing the subject line.
I also added Rob's Reviewed-by: tag from v2.

Guenter

> ---
>  .../devicetree/bindings/hwmon/amd,sbtsi.yaml  | 54 +++++++++++++++++++
>  1 file changed, 54 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> new file mode 100644
> index 000000000000..446b09f1ce94
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/amd,sbtsi.yaml
> @@ -0,0 +1,54 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/hwmon/amd,sbtsi.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: >
> +  Sideband interface Temperature Sensor Interface (SB-TSI) compliant
> +  AMD SoC temperature device
> +
> +maintainers:
> +  - Kun Yi <kunyi@google.com>
> +  - Supreeth Venkatesh <supreeth.venkatesh@amd.com>
> +
> +description: |
> +  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. The emulated thermal sensor can report temperatures in increments
> +  of 0.125 degrees, ranging from 0 to 255.875.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - amd,sbtsi
> +
> +  reg:
> +    maxItems: 1
> +    description: |
> +      I2C bus address of the device as 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.
> +      \[open source SoC register reference\]
> +        https://www.amd.com/system/files/TechDocs/56255_OSRR.pdf
> +
> +required:
> +  - compatible
> +  - reg
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c0 {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        sbtsi@4c {
> +                compatible = "amd,sbtsi";
> +                reg = <0x4c>;
> +        };
> +    };
> +...

Re: [PATCH linux hwmon-next v5 1/3] hwmon: (sbtsi) Add basic support for SB-TSI sensors

[Kun Yi]

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");