1 Kernel driver adm1026 2 ===================== 3 4 Supported 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 15 Authors: 16 - Philip Pokorny <ppokorny@penguincomputing.com> for Penguin Computing 17 - Justin Thiessen <jthiessen@penguincomputing.com> 18 19 Module 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 38 Description 39 ----------- 40 41 This driver implements support for the Analog Devices ADM1026. Analog 42 Devices calls it a "complete thermal system management controller." 43 44 The ADM1026 implements three (3) temperature sensors, 17 voltage sensors, 45 16 general purpose digital I/O lines, eight (8) fan speed sensors (8-bit), 46 an analog output and a PWM output along with limit, alarm and mask bits for 47 all of the above. There is even 8k bytes of EEPROM memory on chip. 48 49 Temperatures are measured in degrees Celsius. There are two external 50 sensor inputs and one internal sensor. Each sensor has a high and low 51 limit. If the limit is exceeded, an interrupt (#SMBALERT) can be 52 generated. The interrupts can be masked. In addition, there are over-temp 53 limits for each sensor. If this limit is exceeded, the #THERM output will 54 be asserted. The current temperature and limits have a resolution of 1 55 degree. 56 57 Fan rotation speeds are reported in RPM (rotations per minute) but measured 58 in counts of a 22.5kHz internal clock. Each fan has a high limit which 59 corresponds to a minimum fan speed. If the limit is exceeded, an interrupt 60 can be generated. Each fan can be programmed to divide the reference clock 61 by 1, 2, 4 or 8. Not all RPM values can accurately be represented, so some 62 rounding is done. With a divider of 8, the slowest measurable speed of a 63 two pulse per revolution fan is 661 RPM. 64 65 There are 17 voltage sensors. An alarm is triggered if the voltage has 66 crossed a programmable minimum or maximum limit. Note that minimum in this 67 case always means 'closest to zero'; this is important for negative voltage 68 measurements. Several inputs have integrated attenuators so they can measure 69 higher voltages directly. 3.3V, 5V, 12V, -12V and battery voltage all have 70 dedicated inputs. There are several inputs scaled to 0-3V full-scale range 71 for SCSI terminator power. The remaining inputs are not scaled and have 72 a 0-2.5V full-scale range. A 2.5V or 1.82V reference voltage is provided 73 for negative voltage measurements. 74 75 If an alarm triggers, it will remain triggered until the hardware register 76 is read at least once. This means that the cause for the alarm may already 77 have disappeared! Note that in the current implementation, all hardware 78 registers are read whenever any data is read (unless it is less than 2.0 79 seconds since the last update). This means that you can easily miss 80 once-only alarms. 81 82 The ADM1026 measures continuously. Analog inputs are measured about 4 83 times a second. Fan speed measurement time depends on fan speed and 84 divisor. It can take as long as 1.5 seconds to measure all fan speeds. 85 86 The ADM1026 has the ability to automatically control fan speed based on the 87 temperature sensor inputs. Both the PWM output and the DAC output can be 88 used to control fan speed. Usually only one of these two outputs will be 89 used. Write the minimum PWM or DAC value to the appropriate control 90 register. Then set the low temperature limit in the tmin values for each 91 temperature sensor. The range of control is fixed at 20 °C, and the 92 largest difference between current and tmin of the temperature sensors sets 93 the control output. See the datasheet for several example circuits for 94 controlling fan speed with the PWM and DAC outputs. The fan speed sensors 95 do not have PWM compensation, so it is probably best to control the fan 96 voltage from the power lead rather than on the ground lead. 97 98 The datasheet shows an example application with VID signals attached to 99 GPIO lines. Unfortunately, the chip may not be connected to the VID lines 100 in this way. The driver assumes that the chips *is* connected this way to 101 get a VID voltage.
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