diff options
Diffstat (limited to 'Documentation/hwmon/ltc4245.rst')
| -rw-r--r-- | Documentation/hwmon/ltc4245.rst | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/Documentation/hwmon/ltc4245.rst b/Documentation/hwmon/ltc4245.rst new file mode 100644 index 000000000000..3dafd08a4e87 --- /dev/null +++ b/Documentation/hwmon/ltc4245.rst @@ -0,0 +1,111 @@ +Kernel driver ltc4245 +===================== + +Supported chips: + + * Linear Technology LTC4245 + + Prefix: 'ltc4245' + + Addresses scanned: 0x20-0x3f + + Datasheet: + + http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517 + +Author: Ira W. Snyder <iws@ovro.caltech.edu> + + +Description +----------- + +The LTC4245 controller allows a board to be safely inserted and removed +from a live backplane in multiple supply systems such as CompactPCI and +PCI Express. + + +Usage Notes +----------- + +This driver does not probe for LTC4245 devices, due to the fact that some +of the possible addresses are unfriendly to probing. You will have to +instantiate the devices explicitly. + +Example: the following will load the driver for an LTC4245 at address 0x23 +on I2C bus #1:: + + $ modprobe ltc4245 + $ echo ltc4245 0x23 > /sys/bus/i2c/devices/i2c-1/new_device + + +Sysfs entries +------------- + +The LTC4245 has built-in limits for over and under current warnings. This +makes it very likely that the reference circuit will be used. + +This driver uses the values in the datasheet to change the register values +into the values specified in the sysfs-interface document. The current readings +rely on the sense resistors listed in Table 2: "Sense Resistor Values". + +======================= ======================================================= +in1_input 12v input voltage (mV) +in2_input 5v input voltage (mV) +in3_input 3v input voltage (mV) +in4_input Vee (-12v) input voltage (mV) + +in1_min_alarm 12v input undervoltage alarm +in2_min_alarm 5v input undervoltage alarm +in3_min_alarm 3v input undervoltage alarm +in4_min_alarm Vee (-12v) input undervoltage alarm + +curr1_input 12v current (mA) +curr2_input 5v current (mA) +curr3_input 3v current (mA) +curr4_input Vee (-12v) current (mA) + +curr1_max_alarm 12v overcurrent alarm +curr2_max_alarm 5v overcurrent alarm +curr3_max_alarm 3v overcurrent alarm +curr4_max_alarm Vee (-12v) overcurrent alarm + +in5_input 12v output voltage (mV) +in6_input 5v output voltage (mV) +in7_input 3v output voltage (mV) +in8_input Vee (-12v) output voltage (mV) + +in5_min_alarm 12v output undervoltage alarm +in6_min_alarm 5v output undervoltage alarm +in7_min_alarm 3v output undervoltage alarm +in8_min_alarm Vee (-12v) output undervoltage alarm + +in9_input GPIO voltage data (see note 1) +in10_input GPIO voltage data (see note 1) +in11_input GPIO voltage data (see note 1) + +power1_input 12v power usage (mW) +power2_input 5v power usage (mW) +power3_input 3v power usage (mW) +power4_input Vee (-12v) power usage (mW) +======================= ======================================================= + + +Note 1 +------ + +If you have NOT configured the driver to sample all GPIO pins as analog +voltages, then the in10_input and in11_input sysfs attributes will not be +created. The driver will sample the GPIO pin that is currently connected to the +ADC as an analog voltage, and report the value in in9_input. + +If you have configured the driver to sample all GPIO pins as analog voltages, +then they will be sampled in round-robin fashion. If userspace reads too +slowly, -EAGAIN will be returned when you read the sysfs attribute containing +the sensor reading. + +The LTC4245 chip can be configured to sample all GPIO pins with two methods: + +1) platform data -- see include/linux/platform_data/ltc4245.h +2) OF device tree -- add the "ltc4245,use-extra-gpios" property to each chip + +The default mode of operation is to sample a single GPIO pin. |