adm1026.rst 4.5 KB

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