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| -rw-r--r-- | Documentation/hwmon/vt1211 | 188 |
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diff --git a/Documentation/hwmon/vt1211 b/Documentation/hwmon/vt1211 new file mode 100644 index 000000000000..d6d807138195 --- /dev/null +++ b/Documentation/hwmon/vt1211 @@ -0,0 +1,188 @@ +Kernel driver vt1211 +==================== + +Supported chips: + * VIA VT1211 + Prefix: 'vt1211' + Addresses scanned: none, address read from Super-I/O config space + Datasheet: Provided by VIA upon request and under NDA + +Authors: Juerg Haefliger <juergh@gmail.com> + +This driver is based on the driver for kernel 2.4 by Mark D. Studebaker and +its port to kernel 2.6 by Lars Ekman. + +Thanks to Joseph Chan and Fiona Gatt from VIA for providing documentation and +technical support. + + +Description +----------- + +The VIA VT1211 Super-I/O chip includes complete hardware monitoring +capabilities. It monitors 2 dedicated temperature sensor inputs (temp1 and +temp2), 1 dedicated voltage (in5) and 2 fans. Additionally, the chip +implements 5 universal input channels (UCH1-5) that can be individually +programmed to either monitor a voltage or a temperature. + +This chip also provides manual and automatic control of fan speeds (according +to the datasheet). The driver only supports automatic control since the manual +mode doesn't seem to work as advertised in the datasheet. In fact I couldn't +get manual mode to work at all! Be aware that automatic mode hasn't been +tested very well (due to the fact that my EPIA M10000 doesn't have the fans +connected to the PWM outputs of the VT1211 :-(). + +The following table shows the relationship between the vt1211 inputs and the +sysfs nodes. + +Sensor Voltage Mode Temp Mode Default Use (from the datasheet) +------ ------------ --------- -------------------------------- +Reading 1 temp1 Intel thermal diode +Reading 3 temp2 Internal thermal diode +UCH1/Reading2 in0 temp3 NTC type thermistor +UCH2 in1 temp4 +2.5V +UCH3 in2 temp5 VccP (processor core) +UCH4 in3 temp6 +5V +UCH5 in4 temp7 +12V ++3.3V in5 Internal VCC (+3.3V) + + +Voltage Monitoring +------------------ + +Voltages are sampled by an 8-bit ADC with a LSB of ~10mV. The supported input +range is thus from 0 to 2.60V. Voltage values outside of this range need +external scaling resistors. This external scaling needs to be compensated for +via compute lines in sensors.conf, like: + +compute inx @*(1+R1/R2), @/(1+R1/R2) + +The board level scaling resistors according to VIA's recommendation are as +follows. And this is of course totally dependent on the actual board +implementation :-) You will have to find documentation for your own +motherboard and edit sensors.conf accordingly. + + Expected +Voltage R1 R2 Divider Raw Value +----------------------------------------------- ++2.5V 2K 10K 1.2 2083 mV +VccP --- --- 1.0 1400 mV (1) ++5V 14K 10K 2.4 2083 mV ++12V 47K 10K 5.7 2105 mV ++3.3V (int) 2K 3.4K 1.588 3300 mV (2) ++3.3V (ext) 6.8K 10K 1.68 1964 mV + +(1) Depending on the CPU (1.4V is for a VIA C3 Nehemiah). +(2) R1 and R2 for 3.3V (int) are internal to the VT1211 chip and the driver + performs the scaling and returns the properly scaled voltage value. + +Each measured voltage has an associated low and high limit which triggers an +alarm when crossed. + + +Temperature Monitoring +---------------------- + +Temperatures are reported in millidegree Celsius. Each measured temperature +has a high limit which triggers an alarm if crossed. There is an associated +hysteresis value with each temperature below which the temperature has to drop +before the alarm is cleared (this is only true for interrupt mode 0). The +interrupt mode can be forced to 0 in case the BIOS doesn't do it +automatically. For that, the parameter int_mode=0 needs to be supplied when +loading the driver module. Be aware that overriding BIOS defaults might cause +some unwanted side effects! + +All temperature channels except temp2 are external. Temp2 is the VT1211 +internal thermal diode and the driver does all the scaling for temp2 and +returns the temperature in millidegree Celsius. For the external channels +temp1 and temp3-temp7, scaling depends on the board implementation and needs +to be performed in userspace via sensors.conf. + +Temp1 is an Intel-type thermal diode which requires the following formula to +convert between sysfs readings and real temperatures: + +compute temp1 (@-Offset)/Gain, (@*Gain)+Offset + +According to the VIA VT1211 BIOS porting guide, the following gain and offset +values should be used: + +Diode Type Offset Gain +---------- ------ ---- +Intel CPU 88.638 0.9528 + 65.000 0.9686 *) +VIA C3 Ezra 83.869 0.9528 +VIA C3 Ezra-T 73.869 0.9528 + +*) This is the formula from the lm_sensors 2.10.0 sensors.conf file. I don't +know where it comes from or how it was derived, it's just listed here for +completeness. + +Temp3-temp7 support NTC thermistors. For these channels, the driver returns +the voltages as seen at the individual pins of UCH1-UCH5. The voltage at the +pin (Vpin) is formed by a voltage divider made of the thermistor (Rth) and a +scaling resistor (Rs): + +Vpin = 2200 * Rth / (Rs + Rth) (2200 is the ADC max limit of 2200 mV) + +The equation for the thermistor is as follows (google it if you want to know +more about it): + +Rth = Ro * exp(B * (1 / T - 1 / To)) (To is 298.15K (25C) and Ro is the + nominal resistance at 25C) + +Mingling the above two equations and assuming Rs = Ro and B = 3435 yields the +following formula for sensors.conf: + +compute tempx 1 / (1 / 298.15 - (` (2200 / @ - 1)) / 3435) - 273.15, + 2200 / (1 + (^ (3435 / 298.15 - 3435 / (273.15 + @)))) + + +Fan Speed Control +----------------- + +The VT1211 provides 2 programmable PWM outputs to control the speeds of 2 +fans. Writing a 2 to any of the two pwm[1-2]_enable sysfs nodes will put the +PWM controller in automatic mode. There is only a single controller that +controls both PWM outputs but each PWM output can be individually enabled and +disabled. + +Each PWM has 4 associated distinct output duty-cycles: full, high, low and +off. Full and off are internally hard-wired to 255 (100%) and 0 (0%), +respectively. High and low can be programmed via +pwm[1-2]_auto_point[2-3]_pwm. Each PWM output can be associated with a +different thermal input but - and here's the weird part - only one set of +thermal thresholds exist that controls both PWMs output duty-cycles. The +thermal thresholds are accessible via pwm[1-2]_auto_point[1-4]_temp. Note +that even though there are 2 sets of 4 auto points each, they map to the same +registers in the VT1211 and programming one set is sufficient (actually only +the first set pwm1_auto_point[1-4]_temp is writable, the second set is +read-only). + +PWM Auto Point PWM Output Duty-Cycle +------------------------------------------------ +pwm[1-2]_auto_point4_pwm full speed duty-cycle (hard-wired to 255) +pwm[1-2]_auto_point3_pwm high speed duty-cycle +pwm[1-2]_auto_point2_pwm low speed duty-cycle +pwm[1-2]_auto_point1_pwm off duty-cycle (hard-wired to 0) + +Temp Auto Point Thermal Threshold +--------------------------------------------- +pwm[1-2]_auto_point4_temp full speed temp +pwm[1-2]_auto_point3_temp high speed temp +pwm[1-2]_auto_point2_temp low speed temp +pwm[1-2]_auto_point1_temp off temp + +Long story short, the controller implements the following algorithm to set the +PWM output duty-cycle based on the input temperature: + +Thermal Threshold Output Duty-Cycle + (Rising Temp) (Falling Temp) +---------------------------------------------------------- + full speed duty-cycle full speed duty-cycle +full speed temp + high speed duty-cycle full speed duty-cycle +high speed temp + low speed duty-cycle high speed duty-cycle +low speed temp + off duty-cycle low speed duty-cycle +off temp |