ltc4245.rst (3491B)
1Kernel driver ltc4245 2===================== 3 4Supported chips: 5 6 * Linear Technology LTC4245 7 8 Prefix: 'ltc4245' 9 10 Addresses scanned: 0x20-0x3f 11 12 Datasheet: 13 14 http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517 15 16Author: Ira W. Snyder <iws@ovro.caltech.edu> 17 18 19Description 20----------- 21 22The LTC4245 controller allows a board to be safely inserted and removed 23from a live backplane in multiple supply systems such as CompactPCI and 24PCI Express. 25 26 27Usage Notes 28----------- 29 30This driver does not probe for LTC4245 devices, due to the fact that some 31of the possible addresses are unfriendly to probing. You will have to 32instantiate the devices explicitly. 33 34Example: the following will load the driver for an LTC4245 at address 0x23 35on I2C bus #1:: 36 37 $ modprobe ltc4245 38 $ echo ltc4245 0x23 > /sys/bus/i2c/devices/i2c-1/new_device 39 40 41Sysfs entries 42------------- 43 44The LTC4245 has built-in limits for over and under current warnings. This 45makes it very likely that the reference circuit will be used. 46 47This driver uses the values in the datasheet to change the register values 48into the values specified in the sysfs-interface document. The current readings 49rely on the sense resistors listed in Table 2: "Sense Resistor Values". 50 51======================= ======================================================= 52in1_input 12v input voltage (mV) 53in2_input 5v input voltage (mV) 54in3_input 3v input voltage (mV) 55in4_input Vee (-12v) input voltage (mV) 56 57in1_min_alarm 12v input undervoltage alarm 58in2_min_alarm 5v input undervoltage alarm 59in3_min_alarm 3v input undervoltage alarm 60in4_min_alarm Vee (-12v) input undervoltage alarm 61 62curr1_input 12v current (mA) 63curr2_input 5v current (mA) 64curr3_input 3v current (mA) 65curr4_input Vee (-12v) current (mA) 66 67curr1_max_alarm 12v overcurrent alarm 68curr2_max_alarm 5v overcurrent alarm 69curr3_max_alarm 3v overcurrent alarm 70curr4_max_alarm Vee (-12v) overcurrent alarm 71 72in5_input 12v output voltage (mV) 73in6_input 5v output voltage (mV) 74in7_input 3v output voltage (mV) 75in8_input Vee (-12v) output voltage (mV) 76 77in5_min_alarm 12v output undervoltage alarm 78in6_min_alarm 5v output undervoltage alarm 79in7_min_alarm 3v output undervoltage alarm 80in8_min_alarm Vee (-12v) output undervoltage alarm 81 82in9_input GPIO voltage data (see note 1) 83in10_input GPIO voltage data (see note 1) 84in11_input GPIO voltage data (see note 1) 85 86power1_input 12v power usage (mW) 87power2_input 5v power usage (mW) 88power3_input 3v power usage (mW) 89power4_input Vee (-12v) power usage (mW) 90======================= ======================================================= 91 92 93Note 1 94------ 95 96If you have NOT configured the driver to sample all GPIO pins as analog 97voltages, then the in10_input and in11_input sysfs attributes will not be 98created. The driver will sample the GPIO pin that is currently connected to the 99ADC as an analog voltage, and report the value in in9_input. 100 101If you have configured the driver to sample all GPIO pins as analog voltages, 102then they will be sampled in round-robin fashion. If userspace reads too 103slowly, -EAGAIN will be returned when you read the sysfs attribute containing 104the sensor reading. 105 106The LTC4245 chip can be configured to sample all GPIO pins with two methods: 107 1081) platform data -- see include/linux/platform_data/ltc4245.h 1092) OF device tree -- add the "ltc4245,use-extra-gpios" property to each chip 110 111The default mode of operation is to sample a single GPIO pin.