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