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This version (20 Aug 2019 13:45) was approved by Nuno Sá.
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Table of Contents
LTC2947 High Precision Power and Energy Monitor
Supported Devices
Evaluation Boards
Description
This is a Hardware Monitor subsystem driver. There are two driver's (sharing the same core implementation) for the LTC2947 since the device supports both SPI and I2C interfaces. The underlying bus is abstracted in the core implementation by using regmap. The Hwmon subsystem provides a unified framework for drivers doing hardware monitoring. It exposes a set of sysfs file that should follow the sysfs-interface.
Source Code
Status
Files
| Function | File |
|---|---|
| core driver | drivers/hwmon/ltc2947-core.c |
| driver | drivers/hwmon/ltc2947-i2c.c |
| driver | drivers/hwmon/ltc2947-spi.c |
| core include | drivers/hwmon/ltc2947.h |
Example I2C & SPI device initialization
The LTC2947 supports both I2C and SPI interfaces, so one of the drivers can be used depending on which kind of device is instantiated. Currently, the devices can only be instantiated via device tree.
Required devicetree properties:
- compatible: Must be always one of these:
- adi,ltc2947
- reg: Must be either the I2C device address or the SPI device chip select number.
Example SPI:
&spi0 {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
ltc2947_spi: ltc2947@0 {
compatible = "adi,ltc2947";
reg = <0>;
spi-max-frequency = <1000000>;
};
};
Example I2C:
&i2c0 {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
ltc2947_i2c: ltc2947@5c {
compatible = "adi,ltc2947";
reg = <0x5c>;
};
};
For more supported devicetree properties take a look to dt-bindings.
Enabling Linux driver support
Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”).
The LTC2947 SPI driver depends CONFIG_SPI and the LTC2947 I2C driver depends on CONFIG_I2C.
Adding Linux driver support
Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)
Linux Kernel Configuration
Device Drivers --->
<*> Hardware Monitoring support --->
--- Hardware Monitoring support
[--snip--]
<*> Analog Devices LTC2947 High Precision Power and Energy Monitor over I2C
<*> Analog Devices LTC2947 High Precision Power and Energy Monitor over SPI
[--snip--]
Hardware configuration
Driver testing
HWMON device files
Each and every HWMON device has a device folder under /sys/class/hwmon/hwmonX, where X is the hwmon device index. Under every of these directory folders there are a set of files, depending on what kind of hardware monitoring is supported (temperature, voltage). In order to determine which hwmon device corresponds to which hardware chip, the user can read the name file under /sys/class/hwmon/hwmonX/name.
This specifies any shell prompt running on the target
root:/> cd /sys/class/hwmon/ root:/sys/class/hwmon> ls hwmon0 hwmon1 root:/sys/class/hwmon> cd hwmon1 root:/sys/class/hwmon/hwmon1> ls -l total 0 -r--r--r-- 1 root root 4096 Nov 16 09:25 curr1_fault -r--r--r-- 1 root root 4096 Nov 16 09:25 curr1_highest -r--r--r-- 1 root root 4096 Nov 16 09:25 curr1_input -r--r--r-- 1 root root 4096 Nov 16 09:25 curr1_label -r--r--r-- 1 root root 4096 Nov 16 09:25 curr1_lowest -rw-r--r-- 1 root root 4096 Nov 16 09:25 curr1_max -r--r--r-- 1 root root 4096 Nov 16 09:25 curr1_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 curr1_min -r--r--r-- 1 root root 4096 Nov 16 09:25 curr1_min_alarm --w------- 1 root root 4096 Nov 16 09:25 curr1_reset_history lrwxrwxrwx 1 root root 0 Nov 16 09:25 device -> ../../../spi0.0 -r--r--r-- 1 root root 4096 Nov 16 09:25 energy1_fault -r--r--r-- 1 root root 4096 Nov 16 09:25 energy1_input -rw-r--r-- 1 root root 4096 Nov 16 09:25 energy1_max -r--r--r-- 1 root root 4096 Nov 16 09:25 energy1_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 energy1_min -r--r--r-- 1 root root 4096 Nov 16 09:25 energy1_min_alarm -r--r--r-- 1 root root 4096 Nov 16 09:25 energy1_overflow_alarm -r--r--r-- 1 root root 4096 Nov 16 09:25 energy2_fault -r--r--r-- 1 root root 4096 Nov 16 09:25 energy2_input -rw-r--r-- 1 root root 4096 Nov 16 09:25 energy2_max -r--r--r-- 1 root root 4096 Nov 16 09:25 energy2_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 energy2_min -r--r--r-- 1 root root 4096 Nov 16 09:25 energy2_min_alarm -r--r--r-- 1 root root 4096 Nov 16 09:25 energy2_overflow_alarm -r--r--r-- 1 root root 4096 Nov 16 09:25 in0_fault -r--r--r-- 1 root root 4096 Nov 16 09:25 in0_highest -r--r--r-- 1 root root 4096 Nov 16 09:25 in0_input -r--r--r-- 1 root root 4096 Nov 16 09:25 in0_label -r--r--r-- 1 root root 4096 Nov 16 09:25 in0_lowest -rw-r--r-- 1 root root 4096 Nov 16 09:25 in0_max -r--r--r-- 1 root root 4096 Nov 16 09:25 in0_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 in0_min -r--r--r-- 1 root root 4096 Nov 16 09:25 in0_min_alarm --w------- 1 root root 4096 Nov 16 09:25 in0_reset_history -r--r--r-- 1 root root 4096 Nov 16 09:25 in1_fault -r--r--r-- 1 root root 4096 Nov 16 09:25 in1_highest -r--r--r-- 1 root root 4096 Nov 16 09:25 in1_input -r--r--r-- 1 root root 4096 Nov 16 09:25 in1_label -r--r--r-- 1 root root 4096 Nov 16 09:25 in1_lowest -rw-r--r-- 1 root root 4096 Nov 16 09:25 in1_max -r--r--r-- 1 root root 4096 Nov 16 09:25 in1_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 in1_min -r--r--r-- 1 root root 4096 Nov 16 09:25 in1_min_alarm --w------- 1 root root 4096 Nov 16 09:25 in1_reset_history -r--r--r-- 1 root root 4096 Nov 16 09:21 name lrwxrwxrwx 1 root root 0 Nov 16 09:25 of_node -> ../../../../../../../../../firmware/devicetree/base/soc/spi@7e204000/ltc2947@0 drwxr-xr-x 2 root root 0 Nov 16 09:25 power -r--r--r-- 1 root root 4096 Nov 16 09:25 power1_fault -r--r--r-- 1 root root 4096 Nov 16 09:25 power1_input -r--r--r-- 1 root root 4096 Nov 16 09:25 power1_input_highest -r--r--r-- 1 root root 4096 Nov 16 09:25 power1_input_lowest -r--r--r-- 1 root root 4096 Nov 16 09:25 power1_label -rw-r--r-- 1 root root 4096 Nov 16 09:25 power1_max -r--r--r-- 1 root root 4096 Nov 16 09:25 power1_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 power1_min -r--r--r-- 1 root root 4096 Nov 16 09:25 power1_min_alarm --w------- 1 root root 4096 Nov 16 09:25 power1_reset_history lrwxrwxrwx 1 root root 0 Nov 16 09:25 subsystem -> ../../../../../../../../../class/hwmon -r--r--r-- 1 root root 4096 Nov 16 09:25 temp1_fault -r--r--r-- 1 root root 4096 Nov 16 09:25 temp1_highest -r--r--r-- 1 root root 4096 Nov 16 09:25 temp1_input -r--r--r-- 1 root root 4096 Nov 16 09:25 temp1_label -r--r--r-- 1 root root 4096 Nov 16 09:25 temp1_lowest -rw-r--r-- 1 root root 4096 Nov 16 09:25 temp1_max -r--r--r-- 1 root root 4096 Nov 16 09:25 temp1_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 temp1_min -r--r--r-- 1 root root 4096 Nov 16 09:25 temp1_min_alarm --w------- 1 root root 4096 Nov 16 09:25 temp1_reset_history -r--r--r-- 1 root root 4096 Nov 16 09:25 temp2_label -rw-r--r-- 1 root root 4096 Nov 16 09:25 temp2_max -r--r--r-- 1 root root 4096 Nov 16 09:25 temp2_max_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:25 temp2_min -r--r--r-- 1 root root 4096 Nov 16 09:25 temp2_min_alarm -rw-r--r-- 1 root root 4096 Nov 16 09:17 uevent root:/sys/class/hwmon/hwmon1>
For each type of monitored value (current, power), the file will look like ${type}_${monitored_value}_${channel}, where ${monitored_value} can be the current value, the high threshold, etc… The channel is the index when, for example, a device can monitor more than one voltage. For more information on the files format, take a look to sysfs-interface.
Show device name
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat name ltc2947
Show current values
The device supports readings of current, voltage, power, temperature and energy. To get, for example, the value of the monitored voltage:
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_input 4910
Show highest read value
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_highest 5026
Show lowest read value
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_lowest 4754
Show high threshold
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_max 5500
Show low threshold
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_min 4500
Show high threshold alarm
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_max_alarm 0
Show low threshold alarm
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_min_alarm 0
Show fault
When the ${type}_${channel}_fault files are present, the user can read these files to look for faulty cases. If reading this file returns 1, then the readings for that channel are invalid and should be discarded…
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in0_fault 0
Show label
Some channels, support a label attribute which specifies the name of the channel being monitored.
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat in1_label DVCC
Show Overflow alarm
These properties are custom and not part of the sysfs-hwmon interface. However, the device set's an alarm when register overflow is near for accumulated values (in this case, energy).
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> cat energy1_overflow_alarm 0
Set High threshold
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> echo 5500 > in0_max
Set Low threshold
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> echo 4500 > in0_min
Reset History
This specifies any shell prompt running on the target
root:/sys/class/hwmon/hwmon1> echo 1 > in0_reset_history
More Information
HWMON pointers
- HWMON mailing list: linux [dash] hwmon [at] vger [dot] kernel [dot] org
resources/tools-software/linux-drivers/hwmon/ltc2947.1566301478.txt.gz · Last modified: 20 Aug 2019 13:44 by Nuno Sá