adm1026.rst (4582B)
1Kernel driver adm1026 2===================== 3 4Supported chips: 5 * Analog Devices ADM1026 6 7 Prefix: 'adm1026' 8 9 Addresses scanned: I2C 0x2c, 0x2d, 0x2e 10 11 Datasheet: Publicly available at the Analog Devices website 12 13 https://www.onsemi.com/PowerSolutions/product.do?id=ADM1026 14 15Authors: 16 - Philip Pokorny <ppokorny@penguincomputing.com> for Penguin Computing 17 - Justin Thiessen <jthiessen@penguincomputing.com> 18 19Module Parameters 20----------------- 21 22* gpio_input: int array (min = 1, max = 17) 23 List of GPIO pins (0-16) to program as inputs 24 25* gpio_output: int array (min = 1, max = 17) 26 List of GPIO pins (0-16) to program as outputs 27 28* gpio_inverted: int array (min = 1, max = 17) 29 List of GPIO pins (0-16) to program as inverted 30 31* gpio_normal: int array (min = 1, max = 17) 32 List of GPIO pins (0-16) to program as normal/non-inverted 33 34* gpio_fan: int array (min = 1, max = 8) 35 List of GPIO pins (0-7) to program as fan tachs 36 37 38Description 39----------- 40 41This driver implements support for the Analog Devices ADM1026. Analog 42Devices calls it a "complete thermal system management controller." 43 44The ADM1026 implements three (3) temperature sensors, 17 voltage sensors, 4516 general purpose digital I/O lines, eight (8) fan speed sensors (8-bit), 46an analog output and a PWM output along with limit, alarm and mask bits for 47all of the above. There is even 8k bytes of EEPROM memory on chip. 48 49Temperatures are measured in degrees Celsius. There are two external 50sensor inputs and one internal sensor. Each sensor has a high and low 51limit. If the limit is exceeded, an interrupt (#SMBALERT) can be 52generated. The interrupts can be masked. In addition, there are over-temp 53limits for each sensor. If this limit is exceeded, the #THERM output will 54be asserted. The current temperature and limits have a resolution of 1 55degree. 56 57Fan rotation speeds are reported in RPM (rotations per minute) but measured 58in counts of a 22.5kHz internal clock. Each fan has a high limit which 59corresponds to a minimum fan speed. If the limit is exceeded, an interrupt 60can be generated. Each fan can be programmed to divide the reference clock 61by 1, 2, 4 or 8. Not all RPM values can accurately be represented, so some 62rounding is done. With a divider of 8, the slowest measurable speed of a 63two pulse per revolution fan is 661 RPM. 64 65There are 17 voltage sensors. An alarm is triggered if the voltage has 66crossed a programmable minimum or maximum limit. Note that minimum in this 67case always means 'closest to zero'; this is important for negative voltage 68measurements. Several inputs have integrated attenuators so they can measure 69higher voltages directly. 3.3V, 5V, 12V, -12V and battery voltage all have 70dedicated inputs. There are several inputs scaled to 0-3V full-scale range 71for SCSI terminator power. The remaining inputs are not scaled and have 72a 0-2.5V full-scale range. A 2.5V or 1.82V reference voltage is provided 73for negative voltage measurements. 74 75If an alarm triggers, it will remain triggered until the hardware register 76is read at least once. This means that the cause for the alarm may already 77have disappeared! Note that in the current implementation, all hardware 78registers are read whenever any data is read (unless it is less than 2.0 79seconds since the last update). This means that you can easily miss 80once-only alarms. 81 82The ADM1026 measures continuously. Analog inputs are measured about 4 83times a second. Fan speed measurement time depends on fan speed and 84divisor. It can take as long as 1.5 seconds to measure all fan speeds. 85 86The ADM1026 has the ability to automatically control fan speed based on the 87temperature sensor inputs. Both the PWM output and the DAC output can be 88used to control fan speed. Usually only one of these two outputs will be 89used. Write the minimum PWM or DAC value to the appropriate control 90register. Then set the low temperature limit in the tmin values for each 91temperature sensor. The range of control is fixed at 20 °C, and the 92largest difference between current and tmin of the temperature sensors sets 93the control output. See the datasheet for several example circuits for 94controlling fan speed with the PWM and DAC outputs. The fan speed sensors 95do not have PWM compensation, so it is probably best to control the fan 96voltage from the power lead rather than on the ground lead. 97 98The datasheet shows an example application with VID signals attached to 99GPIO lines. Unfortunately, the chip may not be connected to the VID lines 100in this way. The driver assumes that the chips *is* connected this way to 101get a VID voltage.