[PATCH linux hwmon-next v1 0/3] Add SB-TSI hwmon driver

[PATCH linux hwmon-next v1 0/3] Add SB-TSI hwmon driver

[Kun Yi]

*** BLURB HERE ***
This patchset adds hwmon support for AMD SoC SB-TSI emulated temperature
sensor and related documentation.

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/sbtsi_temp.txt  |  14 ++
 Documentation/hwmon/sbtsi_temp.rst            |  33 +++
 drivers/hwmon/Kconfig                         |  10 +
 drivers/hwmon/Makefile                        |   1 +
 drivers/hwmon/sbtsi_temp.c                    | 218 ++++++++++++++++++
 5 files changed, 276 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/sbtsi_temp.txt
 create mode 100644 Documentation/hwmon/sbtsi_temp.rst
 create mode 100644 drivers/hwmon/sbtsi_temp.c

-- 
2.25.1.696.g5e7596f4ac-goog

[PATCH linux hwmon-next v1 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.

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 | 218 +++++++++++++++++++++++++++++++++++++
 3 files changed, 229 insertions(+)
 create mode 100644 drivers/hwmon/sbtsi_temp.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 05a30832c6ba..9585dcd01d1b 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1412,6 +1412,16 @@ config SENSORS_RASPBERRYPI_HWMON
 	  This driver can also be built as a module. If so, the module
 	  will be called raspberrypi-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 b0b9c8e57176..cd109f003ce4 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -152,6 +152,7 @@ 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..f998d944a515
--- /dev/null
+++ b/drivers/hwmon/sbtsi_temp.c
@@ -0,0 +1,218 @@
+// 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/device.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.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_REG_REV			0xFF /* RO */
+
+#define SBTSI_CONFIG_READ_ORDER_SHIFT	5
+
+#define SBTSI_TEMP_MIN	(0)
+#define SBTSI_TEMP_MAX	(255875)
+#define SBTSI_REV_MAX_VALID_ID	(4)
+
+struct sbtsi_data {
+	struct device *dev;
+	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_REGS_TO_TEMP(s32 integer, s32 decimal)
+{
+	return (((u32)integer << 3) + ((u32)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_TEMP_TO_REGS(u32 temp, u8 *integer, u8 *decimal)
+{
+	temp /= 125;
+	*integer = temp >> 3;
+	*decimal = (temp & 0x7) << 5;
+}
+
+static ssize_t sbtsi_show_temp(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct sbtsi_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	s32 err, temp_int, temp_dec;
+	u8 read_order;
+
+	/*
+	 * 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(client, SBTSI_REG_CONFIG);
+	if (err < 0)
+		return err;
+
+	read_order = (u8)err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT);
+
+	if (read_order == 0) {
+		temp_int = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_INT);
+		temp_dec = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_DEC);
+	} else {
+		temp_dec = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_DEC);
+		temp_int = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_INT);
+	}
+
+	if (temp_int < 0)
+		return temp_int;
+	if (temp_dec < 0)
+		return temp_dec;
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n",
+			 SBTSI_REGS_TO_TEMP(temp_int, temp_dec));
+}
+
+#define sbtsi_show_temp_limit(name, REG) \
+static ssize_t sbtsi_show_##name(struct device *dev, \
+				 struct device_attribute *attr, char *buf) \
+{ \
+	struct sbtsi_data *data = dev_get_drvdata(dev); \
+	struct i2c_client *client = data->client; \
+	s32 temp_int, temp_dec; \
+\
+	temp_int = i2c_smbus_read_byte_data(client, REG##_INT); \
+	temp_dec = i2c_smbus_read_byte_data(client, REG##_DEC); \
+\
+	if (temp_int < 0) \
+		return temp_int; \
+	if (temp_dec < 0) \
+		return temp_dec; \
+\
+	return scnprintf(buf, PAGE_SIZE, "%d\n", \
+			 SBTSI_REGS_TO_TEMP(temp_int, temp_dec)); \
+}
+
+sbtsi_show_temp_limit(temp1_min, SBTSI_REG_TEMP_LOW);
+sbtsi_show_temp_limit(temp1_max, SBTSI_REG_TEMP_HIGH);
+
+#define sbtsi_set_temp_limit(name, REG) \
+static ssize_t sbtsi_set_##name(struct device *dev, \
+				struct device_attribute *attr, \
+				const char *buf, size_t count) \
+{ \
+	struct sbtsi_data *data = dev_get_drvdata(dev); \
+	struct i2c_client *client = data->client; \
+	long val; \
+	u8 temp_int, temp_dec; \
+	int err = kstrtol(buf, 10, &val); \
+	if (err) \
+		return err; \
+\
+	val = clamp_val(val, SBTSI_TEMP_MIN, SBTSI_TEMP_MAX); \
+	mutex_lock(&data->lock); \
+	SBTSI_TEMP_TO_REGS(val, &temp_int, &temp_dec); \
+	i2c_smbus_write_byte_data(client, REG##_INT, temp_int); \
+	i2c_smbus_write_byte_data(client, REG##_DEC, temp_dec); \
+	mutex_unlock(&data->lock); \
+\
+	return count; \
+}
+
+sbtsi_set_temp_limit(temp1_min, SBTSI_REG_TEMP_LOW);
+sbtsi_set_temp_limit(temp1_max, SBTSI_REG_TEMP_HIGH);
+
+static SENSOR_DEVICE_ATTR(temp1_input, 0444, sbtsi_show_temp, NULL, 0);
+static SENSOR_DEVICE_ATTR(temp1_min, 0644, sbtsi_show_temp1_min,
+			  sbtsi_set_temp1_min, 1);
+static SENSOR_DEVICE_ATTR(temp1_max, 0644, sbtsi_show_temp1_max,
+			  sbtsi_set_temp1_max, 2);
+
+static struct attribute *sbtsi_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	&sensor_dev_attr_temp1_min.dev_attr.attr,
+	&sensor_dev_attr_temp1_max.dev_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(sbtsi);
+
+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_groups(dev, client->name, data,
+						       sbtsi_groups);
+	if (IS_ERR(hwmon_dev))
+		return PTR_ERR(hwmon_dev);
+
+	dev_info(dev, "sensor '%s'\n", client->name);
+
+	return 0;
+}
+
+static const struct i2c_device_id sbtsi_id[] = {
+	{"sbtsi", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, sbtsi_id);
+
+static struct i2c_driver sbtsi_driver = {
+	.class = I2C_CLASS_HWMON,
+	.driver = {
+		.name = "sbtsi",
+	},
+	.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");
-- 
2.25.1.696.g5e7596f4ac-goog

[PATCH linux hwmon-next v1 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/sbtsi_temp.rst | 33 ++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 Documentation/hwmon/sbtsi_temp.rst

diff --git a/Documentation/hwmon/sbtsi_temp.rst b/Documentation/hwmon/sbtsi_temp.rst
new file mode 100644
index 000000000000..f5addb72d13f
--- /dev/null
+++ b/Documentation/hwmon/sbtsi_temp.rst
@@ -0,0 +1,33 @@
+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.
+
+    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.
-- 
2.25.1.696.g5e7596f4ac-goog

[PATCH linux hwmon-next v1 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/sbtsi_temp.txt       | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/sbtsi_temp.txt

diff --git a/Documentation/devicetree/bindings/hwmon/sbtsi_temp.txt b/Documentation/devicetree/bindings/hwmon/sbtsi_temp.txt
new file mode 100644
index 000000000000..4020f075699e
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/sbtsi_temp.txt
@@ -0,0 +1,14 @@
+*AMD SoC SB-TSI hwmon driver.
+
+Required properties:
+- compatible: manufacturer and chip name, should be
+	"amd,sbtsi",
+
+- reg: I2C bus address of the device
+
+Example:
+
+sbtsi@4c {
+	compatible = "amd,sbtsi";
+	reg = <0x4c>;
+};
-- 
2.25.1.696.g5e7596f4ac-goog

Re: [PATCH linux hwmon-next v1 1/3] hwmon: (sbtsi) Add basic support for SB-TSI sensors

[Guenter Roeck]

On 3/19/20 3:48 PM, 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.
> 
> Test status: tested reading temp1_input, and reading/writing
> temp1_max/min.
> 

How do I instantiate this driver on a system with an AMD CPU
(in other words, what is the i2c bus and the i2c address) ?

> Signed-off-by: Kun Yi <kunyi@google.com>
> ---
>  drivers/hwmon/Kconfig      |  10 ++
>  drivers/hwmon/Makefile     |   1 +
>  drivers/hwmon/sbtsi_temp.c | 218 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 229 insertions(+)
>  create mode 100644 drivers/hwmon/sbtsi_temp.c
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 05a30832c6ba..9585dcd01d1b 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1412,6 +1412,16 @@ config SENSORS_RASPBERRYPI_HWMON
>  	  This driver can also be built as a module. If so, the module
>  	  will be called raspberrypi-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 b0b9c8e57176..cd109f003ce4 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -152,6 +152,7 @@ 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..f998d944a515
> --- /dev/null
> +++ b/drivers/hwmon/sbtsi_temp.c
> @@ -0,0 +1,218 @@
> +// 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/device.h>
> +#include <linux/init.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.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_REG_REV			0xFF /* RO */
> +
> +#define SBTSI_CONFIG_READ_ORDER_SHIFT	5
> +
> +#define SBTSI_TEMP_MIN	(0)
> +#define SBTSI_TEMP_MAX	(255875)
> +#define SBTSI_REV_MAX_VALID_ID	(4)

Unnecessary ( ) around literals.

> +
> +struct sbtsi_data {
> +	struct device *dev;
> +	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_REGS_TO_TEMP(s32 integer, s32 decimal)
> +{
> +	return (((u32)integer << 3) + ((u32)decimal >> 5)) * 125;

Why pass s32 as parameter just to typecast to u32 ? The values
are known to be between 0 and 255, and thus will never be negative,
even with s32, so this is really unnecessary.

> +}
> +
> +/*
> + * 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_TEMP_TO_REGS(u32 temp, u8 *integer, u8 *decimal)
> +{
> +	temp /= 125;
> +	*integer = temp >> 3;
> +	*decimal = (temp & 0x7) << 5;
> +}
> +
> +static ssize_t sbtsi_show_temp(struct device *dev,
> +			       struct device_attribute *attr, char *buf)
> +{
> +	struct sbtsi_data *data = dev_get_drvdata(dev);
> +	struct i2c_client *client = data->client;
> +	s32 err, temp_int, temp_dec;
> +	u8 read_order;
> +
> +	/*
> +	 * 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(client, SBTSI_REG_CONFIG);
> +	if (err < 0)
> +		return err;
> +
> +	read_order = (u8)err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT);
> +
> +	if (read_order == 0) {
> +		temp_int = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_INT);
> +		temp_dec = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_DEC);
> +	} else {
> +		temp_dec = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_DEC);
> +		temp_int = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_INT);
> +	}
> +
> +	if (temp_int < 0)
> +		return temp_int;
> +	if (temp_dec < 0)
> +		return temp_dec;
> +
> +	return scnprintf(buf, PAGE_SIZE, "%d\n",
> +			 SBTSI_REGS_TO_TEMP(temp_int, temp_dec));
> +}
> +
> +#define sbtsi_show_temp_limit(name, REG) \
> +static ssize_t sbtsi_show_##name(struct device *dev, \
> +				 struct device_attribute *attr, char *buf) \
> +{ \
> +	struct sbtsi_data *data = dev_get_drvdata(dev); \
> +	struct i2c_client *client = data->client; \
> +	s32 temp_int, temp_dec; \
> +\
> +	temp_int = i2c_smbus_read_byte_data(client, REG##_INT); \
> +	temp_dec = i2c_smbus_read_byte_data(client, REG##_DEC); \
> +\
> +	if (temp_int < 0) \
> +		return temp_int; \
> +	if (temp_dec < 0) \
> +		return temp_dec; \
> +\
> +	return scnprintf(buf, PAGE_SIZE, "%d\n", \
> +			 SBTSI_REGS_TO_TEMP(temp_int, temp_dec)); \
> +}
> +
> +sbtsi_show_temp_limit(temp1_min, SBTSI_REG_TEMP_LOW);
> +sbtsi_show_temp_limit(temp1_max, SBTSI_REG_TEMP_HIGH);
> +
> +#define sbtsi_set_temp_limit(name, REG) \
> +static ssize_t sbtsi_set_##name(struct device *dev, \
> +				struct device_attribute *attr, \
> +				const char *buf, size_t count) \
> +{ \
> +	struct sbtsi_data *data = dev_get_drvdata(dev); \
> +	struct i2c_client *client = data->client; \
> +	long val; \
> +	u8 temp_int, temp_dec; \
> +	int err = kstrtol(buf, 10, &val); \
> +	if (err) \
> +		return err; \
> +\
> +	val = clamp_val(val, SBTSI_TEMP_MIN, SBTSI_TEMP_MAX); \
> +	mutex_lock(&data->lock); \
> +	SBTSI_TEMP_TO_REGS(val, &temp_int, &temp_dec); \
> +	i2c_smbus_write_byte_data(client, REG##_INT, temp_int); \
> +	i2c_smbus_write_byte_data(client, REG##_DEC, temp_dec); \
> +	mutex_unlock(&data->lock); \
> +\
> +	return count; \
> +}
> +
> +sbtsi_set_temp_limit(temp1_min, SBTSI_REG_TEMP_LOW);
> +sbtsi_set_temp_limit(temp1_max, SBTSI_REG_TEMP_HIGH);
> +
> +static SENSOR_DEVICE_ATTR(temp1_input, 0444, sbtsi_show_temp, NULL, 0);
> +static SENSOR_DEVICE_ATTR(temp1_min, 0644, sbtsi_show_temp1_min,
> +			  sbtsi_set_temp1_min, 1);
> +static SENSOR_DEVICE_ATTR(temp1_max, 0644, sbtsi_show_temp1_max,
> +			  sbtsi_set_temp1_max, 2);
> +
> +static struct attribute *sbtsi_attrs[] = {
> +	&sensor_dev_attr_temp1_input.dev_attr.attr,
> +	&sensor_dev_attr_temp1_min.dev_attr.attr,
> +	&sensor_dev_attr_temp1_max.dev_attr.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(sbtsi);
> +
> +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_groups(dev, client->name, data,
> +						       sbtsi_groups);

Please rewrite to use the devm_hwmon_device_register_with_info() API.

> +	if (IS_ERR(hwmon_dev))
> +		return PTR_ERR(hwmon_dev);
> +
> +	dev_info(dev, "sensor '%s'\n", client->name);

Is that really valuable / necessary ?

> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id sbtsi_id[] = {
> +	{"sbtsi", 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, sbtsi_id);
> +
> +static struct i2c_driver sbtsi_driver = {
> +	.class = I2C_CLASS_HWMON,
> +	.driver = {
> +		.name = "sbtsi",
> +	},
> +	.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 v1 1/3] hwmon: (sbtsi) Add basic support for SB-TSI sensors

[Kun Yi]

Thanks for the review comments!

On Thu, Mar 19, 2020 at 4:31 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 3/19/20 3:48 PM, 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.
> >
> > Test status: tested reading temp1_input, and reading/writing
> > temp1_max/min.
> >
>
> How do I instantiate this driver on a system with an AMD CPU
> (in other words, what is the i2c bus and the i2c address) ?

The i2c bus number would be the bus connected from BMC to the AMD CPU.
The i2c address is specified in the spec:
Section 6.3.1: 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.

I will add this information to v2 commit message and the Documentation.

>
> > Signed-off-by: Kun Yi <kunyi@google.com>
> > ---
> >  drivers/hwmon/Kconfig      |  10 ++
> >  drivers/hwmon/Makefile     |   1 +
> >  drivers/hwmon/sbtsi_temp.c | 218 +++++++++++++++++++++++++++++++++++++
> >  3 files changed, 229 insertions(+)
> >  create mode 100644 drivers/hwmon/sbtsi_temp.c
> >
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 05a30832c6ba..9585dcd01d1b 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1412,6 +1412,16 @@ config SENSORS_RASPBERRYPI_HWMON
> >         This driver can also be built as a module. If so, the module
> >         will be called raspberrypi-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 b0b9c8e57176..cd109f003ce4 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -152,6 +152,7 @@ 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..f998d944a515
> > --- /dev/null
> > +++ b/drivers/hwmon/sbtsi_temp.c
> > @@ -0,0 +1,218 @@
> > +// 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/device.h>
> > +#include <linux/init.h>
> > +#include <linux/i2c.h>
> > +#include <linux/module.h>
> > +#include <linux/mutex.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.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_REG_REV                        0xFF /* RO */
> > +
> > +#define SBTSI_CONFIG_READ_ORDER_SHIFT        5
> > +
> > +#define SBTSI_TEMP_MIN       (0)
> > +#define SBTSI_TEMP_MAX       (255875)
> > +#define SBTSI_REV_MAX_VALID_ID       (4)
>
> Unnecessary ( ) around literals.

Will fix in v2.

>
> > +
> > +struct sbtsi_data {
> > +     struct device *dev;
> > +     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_REGS_TO_TEMP(s32 integer, s32 decimal)
> > +{
> > +     return (((u32)integer << 3) + ((u32)decimal >> 5)) * 125;
>
> Why pass s32 as parameter just to typecast to u32 ? The values
> are known to be between 0 and 255, and thus will never be negative,
> even with s32, so this is really unnecessary.

That's a good point, will fix in v2.

> > +}
> > +
> > +/*
> > + * 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_TEMP_TO_REGS(u32 temp, u8 *integer, u8 *decimal)
> > +{
> > +     temp /= 125;
> > +     *integer = temp >> 3;
> > +     *decimal = (temp & 0x7) << 5;
> > +}
> > +
> > +static ssize_t sbtsi_show_temp(struct device *dev,
> > +                            struct device_attribute *attr, char *buf)
> > +{
> > +     struct sbtsi_data *data = dev_get_drvdata(dev);
> > +     struct i2c_client *client = data->client;
> > +     s32 err, temp_int, temp_dec;
> > +     u8 read_order;
> > +
> > +     /*
> > +      * 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(client, SBTSI_REG_CONFIG);
> > +     if (err < 0)
> > +             return err;
> > +
> > +     read_order = (u8)err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT);
> > +
> > +     if (read_order == 0) {
> > +             temp_int = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_INT);
> > +             temp_dec = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_DEC);
> > +     } else {
> > +             temp_dec = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_DEC);
> > +             temp_int = i2c_smbus_read_byte_data(client, SBTSI_REG_TEMP_INT);
> > +     }
> > +
> > +     if (temp_int < 0)
> > +             return temp_int;
> > +     if (temp_dec < 0)
> > +             return temp_dec;
> > +
> > +     return scnprintf(buf, PAGE_SIZE, "%d\n",
> > +                      SBTSI_REGS_TO_TEMP(temp_int, temp_dec));
> > +}
> > +
> > +#define sbtsi_show_temp_limit(name, REG) \
> > +static ssize_t sbtsi_show_##name(struct device *dev, \
> > +                              struct device_attribute *attr, char *buf) \
> > +{ \
> > +     struct sbtsi_data *data = dev_get_drvdata(dev); \
> > +     struct i2c_client *client = data->client; \
> > +     s32 temp_int, temp_dec; \
> > +\
> > +     temp_int = i2c_smbus_read_byte_data(client, REG##_INT); \
> > +     temp_dec = i2c_smbus_read_byte_data(client, REG##_DEC); \
> > +\
> > +     if (temp_int < 0) \
> > +             return temp_int; \
> > +     if (temp_dec < 0) \
> > +             return temp_dec; \
> > +\
> > +     return scnprintf(buf, PAGE_SIZE, "%d\n", \
> > +                      SBTSI_REGS_TO_TEMP(temp_int, temp_dec)); \
> > +}
> > +
> > +sbtsi_show_temp_limit(temp1_min, SBTSI_REG_TEMP_LOW);
> > +sbtsi_show_temp_limit(temp1_max, SBTSI_REG_TEMP_HIGH);
> > +
> > +#define sbtsi_set_temp_limit(name, REG) \
> > +static ssize_t sbtsi_set_##name(struct device *dev, \
> > +                             struct device_attribute *attr, \
> > +                             const char *buf, size_t count) \
> > +{ \
> > +     struct sbtsi_data *data = dev_get_drvdata(dev); \
> > +     struct i2c_client *client = data->client; \
> > +     long val; \
> > +     u8 temp_int, temp_dec; \
> > +     int err = kstrtol(buf, 10, &val); \
> > +     if (err) \
> > +             return err; \
> > +\
> > +     val = clamp_val(val, SBTSI_TEMP_MIN, SBTSI_TEMP_MAX); \
> > +     mutex_lock(&data->lock); \
> > +     SBTSI_TEMP_TO_REGS(val, &temp_int, &temp_dec); \
> > +     i2c_smbus_write_byte_data(client, REG##_INT, temp_int); \
> > +     i2c_smbus_write_byte_data(client, REG##_DEC, temp_dec); \
> > +     mutex_unlock(&data->lock); \
> > +\
> > +     return count; \
> > +}
> > +
> > +sbtsi_set_temp_limit(temp1_min, SBTSI_REG_TEMP_LOW);
> > +sbtsi_set_temp_limit(temp1_max, SBTSI_REG_TEMP_HIGH);
> > +
> > +static SENSOR_DEVICE_ATTR(temp1_input, 0444, sbtsi_show_temp, NULL, 0);
> > +static SENSOR_DEVICE_ATTR(temp1_min, 0644, sbtsi_show_temp1_min,
> > +                       sbtsi_set_temp1_min, 1);
> > +static SENSOR_DEVICE_ATTR(temp1_max, 0644, sbtsi_show_temp1_max,
> > +                       sbtsi_set_temp1_max, 2);
> > +
> > +static struct attribute *sbtsi_attrs[] = {
> > +     &sensor_dev_attr_temp1_input.dev_attr.attr,
> > +     &sensor_dev_attr_temp1_min.dev_attr.attr,
> > +     &sensor_dev_attr_temp1_max.dev_attr.attr,
> > +     NULL,
> > +};
> > +ATTRIBUTE_GROUPS(sbtsi);
> > +
> > +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_groups(dev, client->name, data,
> > +                                                    sbtsi_groups);
>
> Please rewrite to use the devm_hwmon_device_register_with_info() API.

Done in v2.

>
> > +     if (IS_ERR(hwmon_dev))
> > +             return PTR_ERR(hwmon_dev);
> > +
> > +     dev_info(dev, "sensor '%s'\n", client->name);
>
> Is that really valuable / necessary ?

Removed in v2.

>
> > +
> > +     return 0;
> > +}
> > +
> > +static const struct i2c_device_id sbtsi_id[] = {
> > +     {"sbtsi", 0},
> > +     {}
> > +};
> > +MODULE_DEVICE_TABLE(i2c, sbtsi_id);
> > +
> > +static struct i2c_driver sbtsi_driver = {
> > +     .class = I2C_CLASS_HWMON,
> > +     .driver = {
> > +             .name = "sbtsi",
> > +     },
> > +     .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");
> >
>


--
Regards,
Kun