| 1 | Kernel driver adm1026 |
| 2 | ===================== |
| 3 | |
| 4 | Supported 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.analog.com/en/prod/0,,766_825_ADM1026,00.html |
| 10 | |
| 11 | Authors: |
| 12 | Philip Pokorny <ppokorny@penguincomputing.com> for Penguin Computing |
| 13 | Justin Thiessen <jthiessen@penguincomputing.com> |
| 14 | |
| 15 | Module 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 | |
| 30 | Description |
| 31 | ----------- |
| 32 | |
| 33 | This driver implements support for the Analog Devices ADM1026. Analog |
| 34 | Devices calls it a "complete thermal system management controller." |
| 35 | |
| 36 | The ADM1026 implements three (3) temperature sensors, 17 voltage sensors, |
| 37 | 16 general purpose digital I/O lines, eight (8) fan speed sensors (8-bit), |
| 38 | an analog output and a PWM output along with limit, alarm and mask bits for |
| 39 | all of the above. There is even 8k bytes of EEPROM memory on chip. |
| 40 | |
| 41 | Temperatures are measured in degrees Celsius. There are two external |
| 42 | sensor inputs and one internal sensor. Each sensor has a high and low |
| 43 | limit. If the limit is exceeded, an interrupt (#SMBALERT) can be |
| 44 | generated. The interrupts can be masked. In addition, there are over-temp |
| 45 | limits for each sensor. If this limit is exceeded, the #THERM output will |
| 46 | be asserted. The current temperature and limits have a resolution of 1 |
| 47 | degree. |
| 48 | |
| 49 | Fan rotation speeds are reported in RPM (rotations per minute) but measured |
| 50 | in counts of a 22.5kHz internal clock. Each fan has a high limit which |
| 51 | corresponds to a minimum fan speed. If the limit is exceeded, an interrupt |
| 52 | can be generated. Each fan can be programmed to divide the reference clock |
| 53 | by 1, 2, 4 or 8. Not all RPM values can accurately be represented, so some |
| 54 | rounding is done. With a divider of 8, the slowest measurable speed of a |
| 55 | two pulse per revolution fan is 661 RPM. |
| 56 | |
| 57 | There are 17 voltage sensors. An alarm is triggered if the voltage has |
| 58 | crossed a programmable minimum or maximum limit. Note that minimum in this |
| 59 | case always means 'closest to zero'; this is important for negative voltage |
| 60 | measurements. Several inputs have integrated attenuators so they can measure |
| 61 | higher voltages directly. 3.3V, 5V, 12V, -12V and battery voltage all have |
| 62 | dedicated inputs. There are several inputs scaled to 0-3V full-scale range |
| 63 | for SCSI terminator power. The remaining inputs are not scaled and have |
| 64 | a 0-2.5V full-scale range. A 2.5V or 1.82V reference voltage is provided |
| 65 | for negative voltage measurements. |
| 66 | |
| 67 | If an alarm triggers, it will remain triggered until the hardware register |
| 68 | is read at least once. This means that the cause for the alarm may already |
| 69 | have disappeared! Note that in the current implementation, all hardware |
| 70 | registers are read whenever any data is read (unless it is less than 2.0 |
| 71 | seconds since the last update). This means that you can easily miss |
| 72 | once-only alarms. |
| 73 | |
| 74 | The ADM1026 measures continuously. Analog inputs are measured about 4 |
| 75 | times a second. Fan speed measurement time depends on fan speed and |
| 76 | divisor. It can take as long as 1.5 seconds to measure all fan speeds. |
| 77 | |
| 78 | The ADM1026 has the ability to automatically control fan speed based on the |
| 79 | temperature sensor inputs. Both the PWM output and the DAC output can be |
| 80 | used to control fan speed. Usually only one of these two outputs will be |
| 81 | used. Write the minimum PWM or DAC value to the appropriate control |
| 82 | register. Then set the low temperature limit in the tmin values for each |
| 83 | temperature sensor. The range of control is fixed at 20 °C, and the |
| 84 | largest difference between current and tmin of the temperature sensors sets |
| 85 | the control output. See the datasheet for several example circuits for |
| 86 | controlling fan speed with the PWM and DAC outputs. The fan speed sensors |
| 87 | do not have PWM compensation, so it is probably best to control the fan |
| 88 | voltage from the power lead rather than on the ground lead. |
| 89 | |
| 90 | The datasheet shows an example application with VID signals attached to |
| 91 | GPIO lines. Unfortunately, the chip may not be connected to the VID lines |
| 92 | in this way. The driver assumes that the chips *is* connected this way to |
| 93 | get a VID voltage. |