1 Kernel driver adm9240
2 =====================
3
4 Supported chips:
5 * Analog Devices ADM9240
6 Prefix: 'adm9240'
7 Addresses scanned: I2C 0x2c - 0x2f
8 Datasheet: Publicly available at the Analog Devices website
9 http://www.analog.com/UploadedFiles/Data_Sheets/79857778ADM9240_0.pdf
10
11 * Dallas Semiconductor DS1780
12 Prefix: 'ds1780'
13 Addresses scanned: I2C 0x2c - 0x2f
14 Datasheet: Publicly available at the Dallas Semiconductor (Maxim) website
15 http://pdfserv.maxim-ic.com/en/ds/DS1780.pdf
16
17 * National Semiconductor LM81
18 Prefix: 'lm81'
19 Addresses scanned: I2C 0x2c - 0x2f
20 Datasheet: Publicly available at the National Semiconductor website
21 http://www.national.com/ds.cgi/LM/LM81.pdf
22
23 Authors:
24 Frodo Looijaard <frodol@dds.nl>,
25 Philip Edelbrock <phil@netroedge.com>,
26 Michiel Rook <michiel@grendelproject.nl>,
27 Grant Coady <gcoady@gmail.com> with guidance
28 from Jean Delvare <khali@linux-fr.org>
29
30 Interface
31 ---------
32 The I2C addresses listed above assume BIOS has not changed the
33 chip MSB 5-bit address. Each chip reports a unique manufacturer
34 identification code as well as the chip revision/stepping level.
35
36 Description
37 -----------
38 [From ADM9240] The ADM9240 is a complete system hardware monitor for
39 microprocessor-based systems, providing measurement and limit comparison
40 of up to four power supplies and two processor core voltages, plus
41 temperature, two fan speeds and chassis intrusion. Measured values can
42 be read out via an I2C-compatible serial System Management Bus, and values
43 for limit comparisons can be programmed in over the same serial bus. The
44 high speed successive approximation ADC allows frequent sampling of all
45 analog channels to ensure a fast interrupt response to any out-of-limit
46 measurement.
47
48 The ADM9240, DS1780 and LM81 are register compatible, the following
49 details are common to the three chips. Chip differences are described
50 after this section.
51
52
53 Measurements
54 ------------
55 The measurement cycle
56
57 The adm9240 driver will take a measurement reading no faster than once
58 each two seconds. User-space may read sysfs interface faster than the
59 measurement update rate and will receive cached data from the most
60 recent measurement.
61
62 ADM9240 has a very fast 320us temperature and voltage measurement cycle
63 with independent fan speed measurement cycles counting alternating rising
64 edges of the fan tacho inputs.
65
66 DS1780 measurement cycle is about once per second including fan speed.
67
68 LM81 measurement cycle is about once per 400ms including fan speed.
69 The LM81 12-bit extended temperature measurement mode is not supported.
70
71 Temperature
72 -----------
73 On chip temperature is reported as degrees Celsius as 9-bit signed data
74 with resolution of 0.5 degrees Celsius. High and low temperature limits
75 are 8-bit signed data with resolution of one degree Celsius.
76
77 Temperature alarm is asserted once the temperature exceeds the high limit,
78 and is cleared when the temperature falls below the temp1_max_hyst value.
79
80 Fan Speed
81 ---------
82 Two fan tacho inputs are provided, the ADM9240 gates an internal 22.5kHz
83 clock via a divider to an 8-bit counter. Fan speed (rpm) is calculated by:
84
85 rpm = (22500 * 60) / (count * divider)
86
87 Automatic fan clock divider
88
89 * User sets 0 to fan_min limit
90 - low speed alarm is disabled
91 - fan clock divider not changed
92 - auto fan clock adjuster enabled for valid fan speed reading
93
94 * User sets fan_min limit too low
95 - low speed alarm is enabled
96 - fan clock divider set to max
97 - fan_min set to register value 254 which corresponds
98 to 664 rpm on adm9240
99 - low speed alarm will be asserted if fan speed is
100 less than minimum measurable speed
101 - auto fan clock adjuster disabled
102
103 * User sets reasonable fan speed
104 - low speed alarm is enabled
105 - fan clock divider set to suit fan_min
106 - auto fan clock adjuster enabled: adjusts fan_min
107
108 * User sets unreasonably high low fan speed limit
109 - resolution of the low speed limit may be reduced
110 - alarm will be asserted
111 - auto fan clock adjuster enabled: adjusts fan_min
112
113 * fan speed may be displayed as zero until the auto fan clock divider
114 adjuster brings fan speed clock divider back into chip measurement
115 range, this will occur within a few measurement cycles.
116
117 Analog Output
118 -------------
119 An analog output provides a 0 to 1.25 volt signal intended for an external
120 fan speed amplifier circuit. The analog output is set to maximum value on
121 power up or reset. This doesn't do much on the test Intel SE440BX-2.
122
123 Voltage Monitor
124
125 Voltage (IN) measurement is internally scaled:
126
127 nr label nominal maximum resolution
128 mV mV mV
129 0 +2.5V 2500 3320 13.0
130 1 Vccp1 2700 3600 14.1
131 2 +3.3V 3300 4380 17.2
132 3 +5V 5000 6640 26.0
133 4 +12V 12000 15940 62.5
134 5 Vccp2 2700 3600 14.1
135
136 The reading is an unsigned 8-bit value, nominal voltage measurement is
137 represented by a reading of 192, being 3/4 of the measurement range.
138
139 An alarm is asserted for any voltage going below or above the set limits.
140
141 The driver reports and accepts voltage limits scaled to the above table.
142
143 VID Monitor
144 -----------
145 The chip has five inputs to read the 5-bit VID and reports the mV value
146 based on detected CPU type.
147
148 Chassis Intrusion
149 -----------------
150 An alarm is asserted when the CI pin goes active high. The ADM9240
151 Datasheet has an example of an external temperature sensor driving
152 this pin. On an Intel SE440BX-2 the Chassis Intrusion header is
153 connected to a normally open switch.
154
155 The ADM9240 provides an internal open drain on this line, and may output
156 a 20 ms active low pulse to reset an external Chassis Intrusion latch.
157
158 Clear the CI latch by writing value 1 to the sysfs chassis_clear file.
159
160 Alarm flags reported as 16-bit word
161
162 bit label comment
163 --- ------------- --------------------------
164 0 +2.5 V_Error high or low limit exceeded
165 1 VCCP_Error high or low limit exceeded
166 2 +3.3 V_Error high or low limit exceeded
167 3 +5 V_Error high or low limit exceeded
168 4 Temp_Error temperature error
169 6 FAN1_Error fan low limit exceeded
170 7 FAN2_Error fan low limit exceeded
171 8 +12 V_Error high or low limit exceeded
172 9 VCCP2_Error high or low limit exceeded
173 12 Chassis_Error CI pin went high
174
175 Remaining bits are reserved and thus undefined. It is important to note
176 that alarm bits may be cleared on read, user-space may latch alarms and
177 provide the end-user with a method to clear alarm memory.
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