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diff --git a/Documentation/hwmon/ltc4282.rst b/Documentation/hwmon/ltc4282.rst new file mode 100644 index 0000000000..a87ec35649 --- /dev/null +++ b/Documentation/hwmon/ltc4282.rst @@ -0,0 +1,133 @@ +.. SPDX-License-Identifier: GPL-2.0-only + +Kernel drivers ltc4282 +========================================== + +Supported chips: + + * Analog Devices LTC4282 + + Prefix: 'ltc4282' + + Addresses scanned: - I2C 0x40 - 0x5A (7-bit) + Addresses scanned: - I2C 0x80 - 0xB4 with a step of 2 (8-bit) + + Datasheet: + + https://www.analog.com/media/en/technical-documentation/data-sheets/ltc4282.pdf + +Author: Nuno Sá <nuno.sa@analog.com> + +Description +___________ + +The LTC4282 hot swap controller allows a board to be safely inserted and removed +from a live backplane. Using one or more external N-channel pass transistors, +board supply voltage and inrush current are ramped up at an adjustable rate. An +I2C interface and onboard ADC allows for monitoring of board current, voltage, +power, energy and fault status. The device features analog foldback current +limiting and supply monitoring for applications from 2.9V to 33V. Dual 12V gate +drive allows high power applications to either share safe operating area across +parallel MOSFETs or support a 2-stage start-up that first charges the load +capacitance followed by enabling a low on-resistance path to the load. The +LTC4282 is well suited to high power applications because the precise monitoring +capability and accurate current limiting reduce the extremes in which both loads +and power supplies must safely operate. Non-volatile configuration allows for +flexibility in the autonomous generation of alerts and response to faults. + +Sysfs entries +_____________ + +The following attributes are supported. Limits are read-write and all the other +attributes are read-only. Note that in0 and in1 are mutually exclusive. Enabling +one disables the other and disabling one enables the other. + +======================= ========================================== +in0_input Output voltage (mV). +in0_min Undervoltage threshold +in0_max Overvoltage threshold +in0_lowest Lowest measured voltage +in0_highest Highest measured voltage +in0_reset_history Write 1 to reset in0 history. + Also clears fet bad and short fault logs. +in0_min_alarm Undervoltage alarm +in0_max_alarm Overvoltage alarm +in0_enable Enable/Disable VSOURCE monitoring +in0_fault Failure in the MOSFETs. Either bad or shorted FET. +in0_label Channel label (VSOURCE) + +in1_input Input voltage (mV). +in1_min Undervoltage threshold +in1_max Overvoltage threshold +in1_lowest Lowest measured voltage +in1_highest Highest measured voltage +in1_reset_history Write 1 to reset in1 history. + Also clears over/undervoltage fault logs. +in1_min_alarm Undervoltage alarm +in1_max_alarm Overvoltage alarm +in1_lcrit_alarm Critical Undervoltage alarm +in1_crit_alarm Critical Overvoltage alarm +in1_enable Enable/Disable VDD monitoring +in1_label Channel label (VDD) + +in2_input GPIO voltage (mV) +in2_min Undervoltage threshold +in2_max Overvoltage threshold +in2_lowest Lowest measured voltage +in2_highest Highest measured voltage +in2_reset_history Write 1 to reset in2 history +in2_min_alarm Undervoltage alarm +in2_max_alarm Overvoltage alarm +in2_label Channel label (VGPIO) + +curr1_input Sense current (mA) +curr1_min Undercurrent threshold +curr1_max Overcurrent threshold +curr1_lowest Lowest measured current +curr1_highest Highest measured current +curr1_reset_history Write 1 to reset curr1 history. + Also clears overcurrent fault logs. +curr1_min_alarm Undercurrent alarm +curr1_max_alarm Overcurrent alarm +curr1_crit_alarm Critical Overcurrent alarm +curr1_label Channel label (ISENSE) + +power1_input Power (in uW) +power1_min Low power threshold +power1_max High power threshold +power1_input_lowest Historical minimum power use +power1_input_highest Historical maximum power use +power1_reset_history Write 1 to reset power1 history. + Also clears power bad fault logs. +power1_min_alarm Low power alarm +power1_max_alarm High power alarm +power1_label Channel label (Power) + +energy1_input Measured energy over time (in microJoule) +energy1_enable Enable/Disable Energy accumulation +======================= ========================================== + +DebugFs entries +_______________ + +The chip also has a fault log register where failures can be logged. Hence, +as these are logging events, we give access to them in debugfs. Note that +even if some failure is detected in these logs, it does necessarily mean +that the failure is still present. As mentioned in the proper Sysfs entries, +these logs can be cleared by writing in the proper reset_history attribute. + +.. warning:: The debugfs interface is subject to change without notice + and is only available when the kernel is compiled with + ``CONFIG_DEBUG_FS`` defined. + +``/sys/kernel/debug/ltc4282-hwmon[X]/`` +contains the following attributes: + +======================= ========================================== +power1_bad_fault_log Set to 1 by a power1 bad fault occurring. +in0_fet_short_fault_log Set to 1 when the ADC detects a FET-short fault. +in0_fet_bad_fault_log Set to 1 when a FET-BAD fault occurs. +in1_crit_fault_log Set to 1 by a VDD overvoltage fault occurring. +in1_lcrit_fault_log Set to 1 by a VDD undervoltage fault occurring. +curr1_crit_fault_log Set to 1 by an overcurrent fault occurring. +======================= ========================================== |