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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

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.onsemi.com/PowerSolutions/product.do?id=ADM1026
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.
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