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diff --git a/Documentation/hwmon/lm63.rst b/Documentation/hwmon/lm63.rst new file mode 100644 index 000000000..9e27367d7 --- /dev/null +++ b/Documentation/hwmon/lm63.rst @@ -0,0 +1,95 @@ +Kernel driver lm63 +================== + +Supported chips: + + * National Semiconductor LM63 + + Prefix: 'lm63' + + Addresses scanned: I2C 0x4c + + Datasheet: Publicly available at the National Semiconductor website + + http://www.national.com/pf/LM/LM63.html + + * National Semiconductor LM64 + + Prefix: 'lm64' + + Addresses scanned: I2C 0x18 and 0x4e + + Datasheet: Publicly available at the National Semiconductor website + + http://www.national.com/pf/LM/LM64.html + + * National Semiconductor LM96163 + + Prefix: 'lm96163' + + Addresses scanned: I2C 0x4c + + Datasheet: Publicly available at the National Semiconductor website + + http://www.national.com/pf/LM/LM96163.html + + +Author: Jean Delvare <jdelvare@suse.de> + +Thanks go to Tyan and especially Alex Buckingham for setting up a remote +access to their S4882 test platform for this driver. + + https://www.tyan.com/ + +Description +----------- + +The LM63 is a digital temperature sensor with integrated fan monitoring +and control. + +The LM63 is basically an LM86 with fan speed monitoring and control +capabilities added. It misses some of the LM86 features though: + + - No low limit for local temperature. + - No critical limit for local temperature. + - Critical limit for remote temperature can be changed only once. We + will consider that the critical limit is read-only. + +The datasheet isn't very clear about what the tachometer reading is. + +An explanation from National Semiconductor: The two lower bits of the read +value have to be masked out. The value is still 16 bit in width. + +All temperature values are given in degrees Celsius. Resolution is 1.0 +degree for the local temperature, 0.125 degree for the remote temperature. + +The fan speed is measured using a tachometer. Contrary to most chips which +store the value in an 8-bit register and have a selectable clock divider +to make sure that the result will fit in the register, the LM63 uses 16-bit +value for measuring the speed of the fan. It can measure fan speeds down to +83 RPM, at least in theory. + +Note that the pin used for fan monitoring is shared with an alert out +function. Depending on how the board designer wanted to use the chip, fan +speed monitoring will or will not be possible. The proper chip configuration +is left to the BIOS, and the driver will blindly trust it. Only the original +LM63 suffers from this limitation, the LM64 and LM96163 have separate pins +for fan monitoring and alert out. On the LM64, monitoring is always enabled; +on the LM96163 it can be disabled. + +A PWM output can be used to control the speed of the fan. The LM63 has two +PWM modes: manual and automatic. Automatic mode is not fully implemented yet +(you cannot define your custom PWM/temperature curve), and mode change isn't +supported either. + +The lm63 driver will not update its values more frequently than configured with +the update_interval sysfs attribute; reading them more often will do no harm, +but will return 'old' values. Values in the automatic fan control lookup table +(attributes pwm1_auto_*) have their own independent lifetime of 5 seconds. + +The LM64 is effectively an LM63 with GPIO lines. The driver does not +support these GPIO lines at present. + +The LM96163 is an enhanced version of LM63 with improved temperature accuracy +and better PWM resolution. For LM96163, the external temperature sensor type is +configurable as CPU embedded diode(1) or 3904 transistor(2). |