0001 Kernel driver lm63
0002 ==================
0003
0004 Supported chips:
0005
0006 * National Semiconductor LM63
0007
0008 Prefix: 'lm63'
0009
0010 Addresses scanned: I2C 0x4c
0011
0012 Datasheet: Publicly available at the National Semiconductor website
0013
0014 http://www.national.com/pf/LM/LM63.html
0015
0016 * National Semiconductor LM64
0017
0018 Prefix: 'lm64'
0019
0020 Addresses scanned: I2C 0x18 and 0x4e
0021
0022 Datasheet: Publicly available at the National Semiconductor website
0023
0024 http://www.national.com/pf/LM/LM64.html
0025
0026 * National Semiconductor LM96163
0027
0028 Prefix: 'lm96163'
0029
0030 Addresses scanned: I2C 0x4c
0031
0032 Datasheet: Publicly available at the National Semiconductor website
0033
0034 http://www.national.com/pf/LM/LM96163.html
0035
0036
0037 Author: Jean Delvare <jdelvare@suse.de>
0038
0039 Thanks go to Tyan and especially Alex Buckingham for setting up a remote
0040 access to their S4882 test platform for this driver.
0041
0042 https://www.tyan.com/
0043
0044 Description
0045 -----------
0046
0047 The LM63 is a digital temperature sensor with integrated fan monitoring
0048 and control.
0049
0050 The LM63 is basically an LM86 with fan speed monitoring and control
0051 capabilities added. It misses some of the LM86 features though:
0052
0053 - No low limit for local temperature.
0054 - No critical limit for local temperature.
0055 - Critical limit for remote temperature can be changed only once. We
0056 will consider that the critical limit is read-only.
0057
0058 The datasheet isn't very clear about what the tachometer reading is.
0059
0060 An explanation from National Semiconductor: The two lower bits of the read
0061 value have to be masked out. The value is still 16 bit in width.
0062
0063 All temperature values are given in degrees Celsius. Resolution is 1.0
0064 degree for the local temperature, 0.125 degree for the remote temperature.
0065
0066 The fan speed is measured using a tachometer. Contrary to most chips which
0067 store the value in an 8-bit register and have a selectable clock divider
0068 to make sure that the result will fit in the register, the LM63 uses 16-bit
0069 value for measuring the speed of the fan. It can measure fan speeds down to
0070 83 RPM, at least in theory.
0071
0072 Note that the pin used for fan monitoring is shared with an alert out
0073 function. Depending on how the board designer wanted to use the chip, fan
0074 speed monitoring will or will not be possible. The proper chip configuration
0075 is left to the BIOS, and the driver will blindly trust it. Only the original
0076 LM63 suffers from this limitation, the LM64 and LM96163 have separate pins
0077 for fan monitoring and alert out. On the LM64, monitoring is always enabled;
0078 on the LM96163 it can be disabled.
0079
0080 A PWM output can be used to control the speed of the fan. The LM63 has two
0081 PWM modes: manual and automatic. Automatic mode is not fully implemented yet
0082 (you cannot define your custom PWM/temperature curve), and mode change isn't
0083 supported either.
0084
0085 The lm63 driver will not update its values more frequently than configured with
0086 the update_interval sysfs attribute; reading them more often will do no harm,
0087 but will return 'old' values. Values in the automatic fan control lookup table
0088 (attributes pwm1_auto_*) have their own independent lifetime of 5 seconds.
0089
0090 The LM64 is effectively an LM63 with GPIO lines. The driver does not
0091 support these GPIO lines at present.
0092
0093 The LM96163 is an enhanced version of LM63 with improved temperature accuracy
0094 and better PWM resolution. For LM96163, the external temperature sensor type is
0095 configurable as CPU embedded diode(1) or 3904 transistor(2).
