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Add LM82 temperature sensor support (similar to the LM83, but less featureful). Signed-off-by: Jordan Crouse <jordan.crouse@amd.com> Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
85 lines
3.6 KiB
Plaintext
85 lines
3.6 KiB
Plaintext
Kernel driver lm83
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==================
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Supported chips:
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* National Semiconductor LM83
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Prefix: 'lm83'
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Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
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Datasheet: Publicly available at the National Semiconductor website
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http://www.national.com/pf/LM/LM83.html
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* National Semiconductor LM82
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Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e
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Datasheet: Publicly available at the National Semiconductor website
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http://www.national.com/pf/LM/LM82.html
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Author: Jean Delvare <khali@linux-fr.org>
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Description
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-----------
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The LM83 is a digital temperature sensor. It senses its own temperature as
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well as the temperature of up to three external diodes. The LM82 is
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a stripped down version of the LM83 that only supports one external diode.
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Both are compatible with many other devices such as the LM84 and all
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other ADM1021 clones. The main difference between the LM83 and the LM84
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in that the later can only sense the temperature of one external diode.
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Using the adm1021 driver for a LM83 should work, but only two temperatures
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will be reported instead of four.
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The LM83 is only found on a handful of motherboards. Both a confirmed
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list and an unconfirmed list follow. If you can confirm or infirm the
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fact that any of these motherboards do actually have an LM83, please
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contact us. Note that the LM90 can easily be misdetected as a LM83.
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Confirmed motherboards:
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SBS P014
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Unconfirmed motherboards:
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Gigabyte GA-8IK1100
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Iwill MPX2
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Soltek SL-75DRV5
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The LM82 is confirmed to have been found on most AMD Geode reference
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designs and test platforms.
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The driver has been successfully tested by Magnus Forsström, who I'd
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like to thank here. More testers will be of course welcome.
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The fact that the LM83 is only scarcely used can be easily explained.
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Most motherboards come with more than just temperature sensors for
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health monitoring. They also have voltage and fan rotation speed
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sensors. This means that temperature-only chips are usually used as
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secondary chips coupled with another chip such as an IT8705F or similar
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chip, which provides more features. Since systems usually need three
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temperature sensors (motherboard, processor, power supply) and primary
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chips provide some temperature sensors, the secondary chip, if needed,
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won't have to handle more than two temperatures. Thus, ADM1021 clones
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are sufficient, and there is no need for a four temperatures sensor
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chip such as the LM83. The only case where using an LM83 would make
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sense is on SMP systems, such as the above-mentioned Iwill MPX2,
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because you want an additional temperature sensor for each additional
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CPU.
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On the SBS P014, this is different, since the LM83 is the only hardware
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monitoring chipset. One temperature sensor is used for the motherboard
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(actually measuring the LM83's own temperature), one is used for the
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CPU. The two other sensors must be used to measure the temperature of
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two other points of the motherboard. We suspect these points to be the
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north and south bridges, but this couldn't be confirmed.
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All temperature values are given in degrees Celsius. Local temperature
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is given within a range of 0 to +85 degrees. Remote temperatures are
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given within a range of 0 to +125 degrees. Resolution is 1.0 degree,
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accuracy is guaranteed to 3.0 degrees (see the datasheet for more
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details).
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Each sensor has its own high limit, but the critical limit is common to
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all four sensors. There is no hysteresis mechanism as found on most
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recent temperature sensors.
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The lm83 driver will not update its values more frequently than every
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other second; reading them more often will do no harm, but will return
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'old' values.
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