1*4882a593SmuzhiyunKernel driver lm78 2*4882a593Smuzhiyun================== 3*4882a593Smuzhiyun 4*4882a593SmuzhiyunSupported chips: 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun * National Semiconductor LM78 / LM78-J 7*4882a593Smuzhiyun 8*4882a593Smuzhiyun Prefix: 'lm78' 9*4882a593Smuzhiyun 10*4882a593Smuzhiyun Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) 11*4882a593Smuzhiyun 12*4882a593Smuzhiyun Datasheet: Publicly available at the National Semiconductor website 13*4882a593Smuzhiyun 14*4882a593Smuzhiyun http://www.national.com/ 15*4882a593Smuzhiyun 16*4882a593Smuzhiyun * National Semiconductor LM79 17*4882a593Smuzhiyun 18*4882a593Smuzhiyun Prefix: 'lm79' 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun Datasheet: Publicly available at the National Semiconductor website 23*4882a593Smuzhiyun 24*4882a593Smuzhiyun http://www.national.com/ 25*4882a593Smuzhiyun 26*4882a593Smuzhiyun 27*4882a593SmuzhiyunAuthors: 28*4882a593Smuzhiyun - Frodo Looijaard <frodol@dds.nl> 29*4882a593Smuzhiyun - Jean Delvare <jdelvare@suse.de> 30*4882a593Smuzhiyun 31*4882a593SmuzhiyunDescription 32*4882a593Smuzhiyun----------- 33*4882a593Smuzhiyun 34*4882a593SmuzhiyunThis driver implements support for the National Semiconductor LM78, LM78-J 35*4882a593Smuzhiyunand LM79. They are described as 'Microprocessor System Hardware Monitors'. 36*4882a593Smuzhiyun 37*4882a593SmuzhiyunThere is almost no difference between the three supported chips. Functionally, 38*4882a593Smuzhiyunthe LM78 and LM78-J are exactly identical. The LM79 has one more VID line, 39*4882a593Smuzhiyunwhich is used to report the lower voltages newer Pentium processors use. 40*4882a593SmuzhiyunFrom here on, LM7* means either of these three types. 41*4882a593Smuzhiyun 42*4882a593SmuzhiyunThe LM7* implements one temperature sensor, three fan rotation speed sensors, 43*4882a593Smuzhiyunseven voltage sensors, VID lines, alarms, and some miscellaneous stuff. 44*4882a593Smuzhiyun 45*4882a593SmuzhiyunTemperatures are measured in degrees Celsius. An alarm is triggered once 46*4882a593Smuzhiyunwhen the Overtemperature Shutdown limit is crossed; it is triggered again 47*4882a593Smuzhiyunas soon as it drops below the Hysteresis value. A more useful behavior 48*4882a593Smuzhiyuncan be found by setting the Hysteresis value to +127 degrees Celsius; in 49*4882a593Smuzhiyunthis case, alarms are issued during all the time when the actual temperature 50*4882a593Smuzhiyunis above the Overtemperature Shutdown value. Measurements are guaranteed 51*4882a593Smuzhiyunbetween -55 and +125 degrees, with a resolution of 1 degree. 52*4882a593Smuzhiyun 53*4882a593SmuzhiyunFan rotation speeds are reported in RPM (rotations per minute). An alarm is 54*4882a593Smuzhiyuntriggered if the rotation speed has dropped below a programmable limit. Fan 55*4882a593Smuzhiyunreadings can be divided by a programmable divider (1, 2, 4 or 8) to give 56*4882a593Smuzhiyunthe readings more range or accuracy. Not all RPM values can accurately be 57*4882a593Smuzhiyunrepresented, so some rounding is done. With a divider of 2, the lowest 58*4882a593Smuzhiyunrepresentable value is around 2600 RPM. 59*4882a593Smuzhiyun 60*4882a593SmuzhiyunVoltage sensors (also known as IN sensors) report their values in volts. 61*4882a593SmuzhiyunAn alarm is triggered if the voltage has crossed a programmable minimum 62*4882a593Smuzhiyunor maximum limit. Note that minimum in this case always means 'closest to 63*4882a593Smuzhiyunzero'; this is important for negative voltage measurements. All voltage 64*4882a593Smuzhiyuninputs can measure voltages between 0 and 4.08 volts, with a resolution 65*4882a593Smuzhiyunof 0.016 volt. 66*4882a593Smuzhiyun 67*4882a593SmuzhiyunThe VID lines encode the core voltage value: the voltage level your processor 68*4882a593Smuzhiyunshould work with. This is hardcoded by the mainboard and/or processor itself. 69*4882a593SmuzhiyunIt is a value in volts. When it is unconnected, you will often find the 70*4882a593Smuzhiyunvalue 3.50 V here. 71*4882a593Smuzhiyun 72*4882a593SmuzhiyunIf an alarm triggers, it will remain triggered until the hardware register 73*4882a593Smuzhiyunis read at least once. This means that the cause for the alarm may 74*4882a593Smuzhiyunalready have disappeared! Note that in the current implementation, all 75*4882a593Smuzhiyunhardware registers are read whenever any data is read (unless it is less 76*4882a593Smuzhiyunthan 1.5 seconds since the last update). This means that you can easily 77*4882a593Smuzhiyunmiss once-only alarms. 78*4882a593Smuzhiyun 79*4882a593SmuzhiyunThe LM7* only updates its values each 1.5 seconds; reading it more often 80*4882a593Smuzhiyunwill do no harm, but will return 'old' values. 81