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authorJuerg Haefliger <juergh@gmail.com>2006-09-24 14:54:46 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2006-09-28 18:31:16 -0400
commit61d0b53363256e87aeb79286be2dc8f62a9d429a (patch)
treeffcb76c1f5280aff408b7200b43c8e705b1ff24f /Documentation/hwmon/vt1211
parentab41319eab3b5e600873dc77dff7756970424ca6 (diff)
vt1211: Add documentation
vt1211: Add documentation Add documentation for the new vt1211 hardware monitoring driver. Signed-off-by: Juerg Haefliger <juergh@gmail.com> Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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1Kernel driver vt1211
2====================
3
4Supported chips:
5 * VIA VT1211
6 Prefix: 'vt1211'
7 Addresses scanned: none, address read from Super-I/O config space
8 Datasheet: Provided by VIA upon request and under NDA
9
10Authors: Juerg Haefliger <juergh@gmail.com>
11
12This driver is based on the driver for kernel 2.4 by Mark D. Studebaker and
13its port to kernel 2.6 by Lars Ekman.
14
15Thanks to Joseph Chan and Fiona Gatt from VIA for providing documentation and
16technical support.
17
18
19Description
20-----------
21
22The VIA VT1211 Super-I/O chip includes complete hardware monitoring
23capabilities. It monitors 2 dedicated temperature sensor inputs (temp1 and
24temp2), 1 dedicated voltage (in5) and 2 fans. Additionally, the chip
25implements 5 universal input channels (UCH1-5) that can be individually
26programmed to either monitor a voltage or a temperature.
27
28This chip also provides manual and automatic control of fan speeds (according
29to the datasheet). The driver only supports automatic control since the manual
30mode doesn't seem to work as advertised in the datasheet. In fact I couldn't
31get manual mode to work at all! Be aware that automatic mode hasn't been
32tested very well (due to the fact that my EPIA M10000 doesn't have the fans
33connected to the PWM outputs of the VT1211 :-().
34
35The following table shows the relationship between the vt1211 inputs and the
36sysfs nodes.
37
38Sensor Voltage Mode Temp Mode Default Use (from the datasheet)
39------ ------------ --------- --------------------------------
40Reading 1 temp1 Intel thermal diode
41Reading 3 temp2 Internal thermal diode
42UCH1/Reading2 in0 temp3 NTC type thermistor
43UCH2 in1 temp4 +2.5V
44UCH3 in2 temp5 VccP (processor core)
45UCH4 in3 temp6 +5V
46UCH5 in4 temp7 +12V
47+3.3V in5 Internal VCC (+3.3V)
48
49
50Voltage Monitoring
51------------------
52
53Voltages are sampled by an 8-bit ADC with a LSB of ~10mV. The supported input
54range is thus from 0 to 2.60V. Voltage values outside of this range need
55external scaling resistors. This external scaling needs to be compensated for
56via compute lines in sensors.conf, like:
57
58compute inx @*(1+R1/R2), @/(1+R1/R2)
59
60The board level scaling resistors according to VIA's recommendation are as
61follows. And this is of course totally dependent on the actual board
62implementation :-) You will have to find documentation for your own
63motherboard and edit sensors.conf accordingly.
64
65 Expected
66Voltage R1 R2 Divider Raw Value
67-----------------------------------------------
68+2.5V 2K 10K 1.2 2083 mV
69VccP --- --- 1.0 1400 mV (1)
70+5V 14K 10K 2.4 2083 mV
71+12V 47K 10K 5.7 2105 mV
72+3.3V (int) 2K 3.4K 1.588 3300 mV (2)
73+3.3V (ext) 6.8K 10K 1.68 1964 mV
74
75(1) Depending on the CPU (1.4V is for a VIA C3 Nehemiah).
76(2) R1 and R2 for 3.3V (int) are internal to the VT1211 chip and the driver
77 performs the scaling and returns the properly scaled voltage value.
78
79Each measured voltage has an associated low and high limit which triggers an
80alarm when crossed.
81
82
83Temperature Monitoring
84----------------------
85
86Temperatures are reported in millidegree Celsius. Each measured temperature
87has a high limit which triggers an alarm if crossed. There is an associated
88hysteresis value with each temperature below which the temperature has to drop
89before the alarm is cleared (this is only true for interrupt mode 0). The
90interrupt mode can be forced to 0 in case the BIOS doesn't do it
91automatically. For that, the parameter int_mode=0 needs to be supplied when
92loading the driver module. Be aware that overriding BIOS defaults might cause
93some unwanted side effects!
94
95All temperature channels except temp2 are external. Temp2 is the VT1211
96internal thermal diode and the driver does all the scaling for temp2 and
97returns the temperature in millidegree Celsius. For the external channels
98temp1 and temp3-temp7, scaling depends on the board implementation and needs
99to be performed in userspace via sensors.conf.
100
101Temp1 is an Intel-type thermal diode which requires the following formula to
102convert between sysfs readings and real temperatures:
103
104compute temp1 (@-Offset)/Gain, (@*Gain)+Offset
105
106According to the VIA VT1211 BIOS porting guide, the following gain and offset
107values should be used:
108
109Diode Type Offset Gain
110---------- ------ ----
111Intel CPU 88.638 0.9528
112 65.000 0.9686 *)
113VIA C3 Ezra 83.869 0.9528
114VIA C3 Ezra-T 73.869 0.9528
115
116*) This is the formula from the lm_sensors 2.10.0 sensors.conf file. I don't
117know where it comes from or how it was derived, it's just listed here for
118completeness.
119
120Temp3-temp7 support NTC thermistors. For these channels, the driver returns
121the voltages as seen at the individual pins of UCH1-UCH5. The voltage at the
122pin (Vpin) is formed by a voltage divider made of the thermistor (Rth) and a
123scaling resistor (Rs):
124
125Vpin = 2200 * Rth / (Rs + Rth) (2200 is the ADC max limit of 2200 mV)
126
127The equation for the thermistor is as follows (google it if you want to know
128more about it):
129
130Rth = Ro * exp(B * (1 / T - 1 / To)) (To is 298.15K (25C) and Ro is the
131 nominal resistance at 25C)
132
133Mingling the above two equations and assuming Rs = Ro and B = 3435 yields the
134following formula for sensors.conf:
135
136compute tempx 1 / (1 / 298.15 - (` (2200 / @ - 1)) / 3435) - 273.15,
137 2200 / (1 + (^ (3435 / 298.15 - 3435 / (273.15 + @))))
138
139
140Fan Speed Control
141-----------------
142
143The VT1211 provides 2 programmable PWM outputs to control the speeds of 2
144fans. Writing a 2 to any of the two pwm[1-2]_enable sysfs nodes will put the
145PWM controller in automatic mode. There is only a single controller that
146controls both PWM outputs but each PWM output can be individually enabled and
147disabled.
148
149Each PWM has 4 associated distinct output duty-cycles: full, high, low and
150off. Full and off are internally hard-wired to 255 (100%) and 0 (0%),
151respectively. High and low can be programmed via
152pwm[1-2]_auto_point[2-3]_pwm. Each PWM output can be associated with a
153different thermal input but - and here's the weird part - only one set of
154thermal thresholds exist that controls both PWMs output duty-cycles. The
155thermal thresholds are accessible via pwm[1-2]_auto_point[1-4]_temp. Note
156that even though there are 2 sets of 4 auto points each, they map to the same
157registers in the VT1211 and programming one set is sufficient (actually only
158the first set pwm1_auto_point[1-4]_temp is writable, the second set is
159read-only).
160
161PWM Auto Point PWM Output Duty-Cycle
162------------------------------------------------
163pwm[1-2]_auto_point4_pwm full speed duty-cycle (hard-wired to 255)
164pwm[1-2]_auto_point3_pwm high speed duty-cycle
165pwm[1-2]_auto_point2_pwm low speed duty-cycle
166pwm[1-2]_auto_point1_pwm off duty-cycle (hard-wired to 0)
167
168Temp Auto Point Thermal Threshold
169---------------------------------------------
170pwm[1-2]_auto_point4_temp full speed temp
171pwm[1-2]_auto_point3_temp high speed temp
172pwm[1-2]_auto_point2_temp low speed temp
173pwm[1-2]_auto_point1_temp off temp
174
175Long story short, the controller implements the following algorithm to set the
176PWM output duty-cycle based on the input temperature:
177
178Thermal Threshold Output Duty-Cycle
179 (Rising Temp) (Falling Temp)
180----------------------------------------------------------
181 full speed duty-cycle full speed duty-cycle
182full speed temp
183 high speed duty-cycle full speed duty-cycle
184high speed temp
185 low speed duty-cycle high speed duty-cycle
186low speed temp
187 off duty-cycle low speed duty-cycle
188off temp