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