94 lines
4.5 KiB
Text
94 lines
4.5 KiB
Text
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Kernel driver adm1026
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=====================
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Supported chips:
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* Analog Devices ADM1026
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Prefix: 'adm1026'
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Addresses scanned: I2C 0x2c, 0x2d, 0x2e
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Datasheet: Publicly available at the Analog Devices website
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http://www.analog.com/en/prod/0,,766_825_ADM1026,00.html
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Authors:
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Philip Pokorny <ppokorny@penguincomputing.com> for Penguin Computing
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Justin Thiessen <jthiessen@penguincomputing.com>
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Module Parameters
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-----------------
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* gpio_input: int array (min = 1, max = 17)
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List of GPIO pins (0-16) to program as inputs
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* gpio_output: int array (min = 1, max = 17)
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List of GPIO pins (0-16) to program as outputs
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* gpio_inverted: int array (min = 1, max = 17)
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List of GPIO pins (0-16) to program as inverted
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* gpio_normal: int array (min = 1, max = 17)
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List of GPIO pins (0-16) to program as normal/non-inverted
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* gpio_fan: int array (min = 1, max = 8)
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List of GPIO pins (0-7) to program as fan tachs
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Description
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-----------
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This driver implements support for the Analog Devices ADM1026. Analog
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Devices calls it a "complete thermal system management controller."
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The ADM1026 implements three (3) temperature sensors, 17 voltage sensors,
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16 general purpose digital I/O lines, eight (8) fan speed sensors (8-bit),
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an analog output and a PWM output along with limit, alarm and mask bits for
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all of the above. There is even 8k bytes of EEPROM memory on chip.
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Temperatures are measured in degrees Celsius. There are two external
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sensor inputs and one internal sensor. Each sensor has a high and low
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limit. If the limit is exceeded, an interrupt (#SMBALERT) can be
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generated. The interrupts can be masked. In addition, there are over-temp
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limits for each sensor. If this limit is exceeded, the #THERM output will
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be asserted. The current temperature and limits have a resolution of 1
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degree.
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Fan rotation speeds are reported in RPM (rotations per minute) but measured
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in counts of a 22.5kHz internal clock. Each fan has a high limit which
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corresponds to a minimum fan speed. If the limit is exceeded, an interrupt
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can be generated. Each fan can be programmed to divide the reference clock
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by 1, 2, 4 or 8. Not all RPM values can accurately be represented, so some
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rounding is done. With a divider of 8, the slowest measurable speed of a
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two pulse per revolution fan is 661 RPM.
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There are 17 voltage sensors. An alarm is triggered if the voltage has
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crossed a programmable minimum or maximum limit. Note that minimum in this
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case always means 'closest to zero'; this is important for negative voltage
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measurements. Several inputs have integrated attenuators so they can measure
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higher voltages directly. 3.3V, 5V, 12V, -12V and battery voltage all have
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dedicated inputs. There are several inputs scaled to 0-3V full-scale range
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for SCSI terminator power. The remaining inputs are not scaled and have
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a 0-2.5V full-scale range. A 2.5V or 1.82V reference voltage is provided
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for negative voltage measurements.
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If an alarm triggers, it will remain triggered until the hardware register
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is read at least once. This means that the cause for the alarm may already
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have disappeared! Note that in the current implementation, all hardware
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registers are read whenever any data is read (unless it is less than 2.0
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seconds since the last update). This means that you can easily miss
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once-only alarms.
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The ADM1026 measures continuously. Analog inputs are measured about 4
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times a second. Fan speed measurement time depends on fan speed and
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divisor. It can take as long as 1.5 seconds to measure all fan speeds.
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The ADM1026 has the ability to automatically control fan speed based on the
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temperature sensor inputs. Both the PWM output and the DAC output can be
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used to control fan speed. Usually only one of these two outputs will be
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used. Write the minimum PWM or DAC value to the appropriate control
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register. Then set the low temperature limit in the tmin values for each
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temperature sensor. The range of control is fixed at 20 <20>C, and the
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largest difference between current and tmin of the temperature sensors sets
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the control output. See the datasheet for several example circuits for
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controlling fan speed with the PWM and DAC outputs. The fan speed sensors
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do not have PWM compensation, so it is probably best to control the fan
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voltage from the power lead rather than on the ground lead.
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The datasheet shows an example application with VID signals attached to
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GPIO lines. Unfortunately, the chip may not be connected to the VID lines
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in this way. The driver assumes that the chips *is* connected this way to
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get a VID voltage.
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