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134 lines
5.2 KiB
ReStructuredText
134 lines
5.2 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0-only
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Kernel drivers ltc4282
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==========================================
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Supported chips:
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* Analog Devices LTC4282
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Prefix: 'ltc4282'
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Addresses scanned: - I2C 0x40 - 0x5A (7-bit)
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Addresses scanned: - I2C 0x80 - 0xB4 with a step of 2 (8-bit)
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Datasheet:
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https://www.analog.com/media/en/technical-documentation/data-sheets/ltc4282.pdf
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Author: Nuno Sá <nuno.sa@analog.com>
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Description
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___________
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The LTC4282 hot swap controller allows a board to be safely inserted and removed
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from a live backplane. Using one or more external N-channel pass transistors,
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board supply voltage and inrush current are ramped up at an adjustable rate. An
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I2C interface and onboard ADC allows for monitoring of board current, voltage,
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power, energy and fault status. The device features analog foldback current
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limiting and supply monitoring for applications from 2.9V to 33V. Dual 12V gate
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drive allows high power applications to either share safe operating area across
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parallel MOSFETs or support a 2-stage start-up that first charges the load
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capacitance followed by enabling a low on-resistance path to the load. The
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LTC4282 is well suited to high power applications because the precise monitoring
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capability and accurate current limiting reduce the extremes in which both loads
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and power supplies must safely operate. Non-volatile configuration allows for
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flexibility in the autonomous generation of alerts and response to faults.
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Sysfs entries
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_____________
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The following attributes are supported. Limits are read-write and all the other
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attributes are read-only. Note that in0 and in1 are mutually exclusive. Enabling
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one disables the other and disabling one enables the other.
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======================= ==========================================
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in0_input Output voltage (mV).
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in0_min Undervoltage threshold
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in0_max Overvoltage threshold
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in0_lowest Lowest measured voltage
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in0_highest Highest measured voltage
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in0_reset_history Write 1 to reset in0 history.
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Also clears fet bad and short fault logs.
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in0_min_alarm Undervoltage alarm
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in0_max_alarm Overvoltage alarm
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in0_enable Enable/Disable VSOURCE monitoring
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in0_fault Failure in the MOSFETs. Either bad or shorted FET.
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in0_label Channel label (VSOURCE)
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in1_input Input voltage (mV).
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in1_min Undervoltage threshold
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in1_max Overvoltage threshold
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in1_lowest Lowest measured voltage
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in1_highest Highest measured voltage
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in1_reset_history Write 1 to reset in1 history.
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Also clears over/undervoltage fault logs.
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in1_min_alarm Undervoltage alarm
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in1_max_alarm Overvoltage alarm
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in1_lcrit_alarm Critical Undervoltage alarm
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in1_crit_alarm Critical Overvoltage alarm
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in1_enable Enable/Disable VDD monitoring
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in1_label Channel label (VDD)
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in2_input GPIO voltage (mV)
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in2_min Undervoltage threshold
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in2_max Overvoltage threshold
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in2_lowest Lowest measured voltage
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in2_highest Highest measured voltage
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in2_reset_history Write 1 to reset in2 history
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in2_min_alarm Undervoltage alarm
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in2_max_alarm Overvoltage alarm
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in2_label Channel label (VGPIO)
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curr1_input Sense current (mA)
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curr1_min Undercurrent threshold
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curr1_max Overcurrent threshold
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curr1_lowest Lowest measured current
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curr1_highest Highest measured current
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curr1_reset_history Write 1 to reset curr1 history.
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Also clears overcurrent fault logs.
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curr1_min_alarm Undercurrent alarm
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curr1_max_alarm Overcurrent alarm
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curr1_crit_alarm Critical Overcurrent alarm
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curr1_label Channel label (ISENSE)
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power1_input Power (in uW)
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power1_min Low power threshold
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power1_max High power threshold
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power1_input_lowest Historical minimum power use
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power1_input_highest Historical maximum power use
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power1_reset_history Write 1 to reset power1 history.
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Also clears power bad fault logs.
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power1_min_alarm Low power alarm
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power1_max_alarm High power alarm
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power1_label Channel label (Power)
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energy1_input Measured energy over time (in microJoule)
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energy1_enable Enable/Disable Energy accumulation
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======================= ==========================================
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DebugFs entries
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_______________
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The chip also has a fault log register where failures can be logged. Hence,
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as these are logging events, we give access to them in debugfs. Note that
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even if some failure is detected in these logs, it does necessarily mean
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that the failure is still present. As mentioned in the proper Sysfs entries,
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these logs can be cleared by writing in the proper reset_history attribute.
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.. warning:: The debugfs interface is subject to change without notice
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and is only available when the kernel is compiled with
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``CONFIG_DEBUG_FS`` defined.
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``/sys/kernel/debug/ltc4282-hwmon[X]/``
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contains the following attributes:
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======================= ==========================================
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power1_bad_fault_log Set to 1 by a power1 bad fault occurring.
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in0_fet_short_fault_log Set to 1 when the ADC detects a FET-short fault.
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in0_fet_bad_fault_log Set to 1 when a FET-BAD fault occurs.
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in1_crit_fault_log Set to 1 by a VDD overvoltage fault occurring.
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in1_lcrit_fault_log Set to 1 by a VDD undervoltage fault occurring.
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curr1_crit_fault_log Set to 1 by an overcurrent fault occurring.
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======================= ==========================================
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