linux/Documentation/hwmon/adm1026
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   1Kernel driver adm1026
   2=====================
   3
   4Supported chips:
   5  * Analog Devices ADM1026
   6    Prefix: 'adm1026'
   7    Addresses scanned: I2C 0x2c, 0x2d, 0x2e
   8    Datasheet: Publicly available at the Analog Devices website
   9               http://www.onsemi.com/PowerSolutions/product.do?id=ADM1026
  10
  11Authors:
  12        Philip Pokorny <ppokorny@penguincomputing.com> for Penguin Computing
  13        Justin Thiessen <jthiessen@penguincomputing.com>
  14
  15Module Parameters
  16-----------------
  17
  18* gpio_input: int array (min = 1, max = 17)
  19  List of GPIO pins (0-16) to program as inputs
  20* gpio_output: int array (min = 1, max = 17)
  21  List of GPIO pins (0-16) to program as outputs
  22* gpio_inverted: int array (min = 1, max = 17)
  23  List of GPIO pins (0-16) to program as inverted
  24* gpio_normal: int array (min = 1, max = 17)
  25  List of GPIO pins (0-16) to program as normal/non-inverted
  26* gpio_fan: int array (min = 1, max = 8)
  27  List of GPIO pins (0-7) to program as fan tachs
  28
  29
  30Description
  31-----------
  32
  33This driver implements support for the Analog Devices ADM1026. Analog
  34Devices calls it a "complete thermal system management controller."
  35
  36The ADM1026 implements three (3) temperature sensors, 17 voltage sensors,
  3716 general purpose digital I/O lines, eight (8) fan speed sensors (8-bit),
  38an analog output and a PWM output along with limit, alarm and mask bits for
  39all of the above. There is even 8k bytes of EEPROM memory on chip.
  40
  41Temperatures are measured in degrees Celsius. There are two external
  42sensor inputs and one internal sensor. Each sensor has a high and low
  43limit. If the limit is exceeded, an interrupt (#SMBALERT) can be
  44generated. The interrupts can be masked. In addition, there are over-temp
  45limits for each sensor. If this limit is exceeded, the #THERM output will
  46be asserted. The current temperature and limits have a resolution of 1
  47degree.
  48
  49Fan rotation speeds are reported in RPM (rotations per minute) but measured
  50in counts of a 22.5kHz internal clock. Each fan has a high limit which
  51corresponds to a minimum fan speed. If the limit is exceeded, an interrupt
  52can be generated. Each fan can be programmed to divide the reference clock
  53by 1, 2, 4 or 8. Not all RPM values can accurately be represented, so some
  54rounding is done. With a divider of 8, the slowest measurable speed of a
  55two pulse per revolution fan is 661 RPM.
  56
  57There are 17 voltage sensors. An alarm is triggered if the voltage has
  58crossed a programmable minimum or maximum limit. Note that minimum in this
  59case always means 'closest to zero'; this is important for negative voltage
  60measurements. Several inputs have integrated attenuators so they can measure
  61higher voltages directly. 3.3V, 5V, 12V, -12V and battery voltage all have
  62dedicated inputs. There are several inputs scaled to 0-3V full-scale range
  63for SCSI terminator power. The remaining inputs are not scaled and have
  64a 0-2.5V full-scale range. A 2.5V or 1.82V reference voltage is provided
  65for negative voltage measurements.
  66
  67If an alarm triggers, it will remain triggered until the hardware register
  68is read at least once. This means that the cause for the alarm may already
  69have disappeared! Note that in the current implementation, all hardware
  70registers are read whenever any data is read (unless it is less than 2.0
  71seconds since the last update). This means that you can easily miss
  72once-only alarms.
  73
  74The ADM1026 measures continuously. Analog inputs are measured about 4
  75times a second. Fan speed measurement time depends on fan speed and
  76divisor. It can take as long as 1.5 seconds to measure all fan speeds.
  77
  78The ADM1026 has the ability to automatically control fan speed based on the
  79temperature sensor inputs. Both the PWM output and the DAC output can be
  80used to control fan speed. Usually only one of these two outputs will be
  81used. Write the minimum PWM or DAC value to the appropriate control
  82register. Then set the low temperature limit in the tmin values for each
  83temperature sensor. The range of control is fixed at 20 °C, and the
  84largest difference between current and tmin of the temperature sensors sets
  85the control output. See the datasheet for several example circuits for
  86controlling fan speed with the PWM and DAC outputs. The fan speed sensors
  87do not have PWM compensation, so it is probably best to control the fan
  88voltage from the power lead rather than on the ground lead.
  89
  90The datasheet shows an example application with VID signals attached to
  91GPIO lines. Unfortunately, the chip may not be connected to the VID lines
  92in this way. The driver assumes that the chips *is* connected this way to
  93get a VID voltage.
  94
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