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Diffstat (limited to 'kernel/Documentation/hwmon/adm1026')
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diff --git a/kernel/Documentation/hwmon/adm1026 b/kernel/Documentation/hwmon/adm1026 new file mode 100644 index 000000000..d8fabe0c2 --- /dev/null +++ b/kernel/Documentation/hwmon/adm1026 @@ -0,0 +1,93 @@ +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. |