| 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. | |
| Module Parameters | |
| ----------------- | |
| * uch_config: int Override the BIOS default universal channel (UCH) | |
| configuration for channels 1-5. | |
| Legal values are in the range of 0-31. Bit 0 maps to | |
| UCH1, bit 1 maps to UCH2 and so on. Setting a bit to 1 | |
| enables the thermal input of that particular UCH and | |
| setting a bit to 0 enables the voltage input. | |
| * int_mode: int Override the BIOS default temperature interrupt mode. | |
| The only possible value is 0 which forces interrupt | |
| mode 0. In this mode, any pending interrupt is cleared | |
| when the status register is read but is regenerated as | |
| long as the temperature stays above the hysteresis | |
| limit. | |
| Be aware that overriding BIOS defaults might cause some unwanted side effects! | |
| 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. See the 'Module Parameters' section for details. | |
| 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 |