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@xxxxxxxxxx>
---
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@xxxxxxxxxx>
+ */
+
+#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@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Hwmon driver for AMD SB-TSI emulated sensor");
+MODULE_LICENSE("GPL");
--
2.25.1.696.g5e7596f4ac-goog
