1Kernel driver lm63 2================== 3 4Supported chips: 5 * National Semiconductor LM63 6 Prefix: 'lm63' 7 Addresses scanned: I2C 0x4c 8 Datasheet: Publicly available at the National Semiconductor website 9 http://www.national.com/pf/LM/LM63.html 10 * National Semiconductor LM64 11 Prefix: 'lm64' 12 Addresses scanned: I2C 0x18 and 0x4e 13 Datasheet: Publicly available at the National Semiconductor website 14 http://www.national.com/pf/LM/LM64.html 15 16Author: Jean Delvare <khali@linux-fr.org> 17 18Thanks go to Tyan and especially Alex Buckingham for setting up a remote 19access to their S4882 test platform for this driver. 20 http://www.tyan.com/ 21 22Description 23----------- 24 25The LM63 is a digital temperature sensor with integrated fan monitoring 26and control. 27 28The LM63 is basically an LM86 with fan speed monitoring and control 29capabilities added. It misses some of the LM86 features though: 30 - No low limit for local temperature. 31 - No critical limit for local temperature. 32 - Critical limit for remote temperature can be changed only once. We 33 will consider that the critical limit is read-only. 34 35The datasheet isn't very clear about what the tachometer reading is. 36 37An explanation from National Semiconductor: The two lower bits of the read 38value have to be masked out. The value is still 16 bit in width. 39 40All temperature values are given in degrees Celsius. Resolution is 1.0 41degree for the local temperature, 0.125 degree for the remote temperature. 42 43The fan speed is measured using a tachometer. Contrary to most chips which 44store the value in an 8-bit register and have a selectable clock divider 45to make sure that the result will fit in the register, the LM63 uses 16-bit 46value for measuring the speed of the fan. It can measure fan speeds down to 4783 RPM, at least in theory. 48 49Note that the pin used for fan monitoring is shared with an alert out 50function. Depending on how the board designer wanted to use the chip, fan 51speed monitoring will or will not be possible. The proper chip configuration 52is left to the BIOS, and the driver will blindly trust it. 53 54A PWM output can be used to control the speed of the fan. The LM63 has two 55PWM modes: manual and automatic. Automatic mode is not fully implemented yet 56(you cannot define your custom PWM/temperature curve), and mode change isn't 57supported either. 58 59The lm63 driver will not update its values more frequently than every 60second; reading them more often will do no harm, but will return 'old' 61values. 62 63The LM64 is effectively an LM63 with GPIO lines. The driver does not 64support these GPIO lines at present. 65