54 lines
2 KiB
Plaintext
54 lines
2 KiB
Plaintext
Kernel driver nsa320_hwmon
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==========================
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Supported chips:
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* Holtek HT46R065 microcontroller with onboard firmware that configures
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it to act as a hardware monitor.
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Prefix: 'nsa320'
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Addresses scanned: none
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Datasheet: Not available, driver was reverse engineered based upon the
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Zyxel kernel source
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Author:
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Adam Baker <linux@baker-net.org.uk>
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Description
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-----------
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This chip is known to be used in the Zyxel NSA320 and NSA325 NAS Units and
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also in some variants of the NSA310 but the driver has only been tested
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on the NSA320. In all of these devices it is connected to the same 3 GPIO
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lines which are used to provide chip select, clock and data lines. The
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interface behaves similarly to SPI but at much lower speeds than are normally
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used for SPI.
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Following each chip select pulse the chip will generate a single 32 bit word
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that contains 0x55 as a marker to indicate that data is being read correctly,
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followed by an 8 bit fan speed in 100s of RPM and a 16 bit temperature in
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tenths of a degree.
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sysfs-Interface
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---------------
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temp1_input - temperature input
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fan1_input - fan speed
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Notes
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-----
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The access timings used in the driver are the same as used in the Zyxel
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provided kernel. Testing has shown that if the delay between chip select and
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the first clock pulse is reduced from 100 ms to just under 10ms then the chip
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will not produce any output. If the duration of either phase of the clock
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is reduced from 100 us to less than 15 us then data pulses are likely to be
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read twice corrupting the output. The above analysis is based upon a sample
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of one unit but suggests that the Zyxel provided delay values include a
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reasonable tolerance.
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The driver incorporates a limit that it will not check for updated values
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faster than once a second. This is because the hardware takes a relatively long
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time to read the data from the device and when it does it reads both temp and
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fan speed. As the most likely case for two accesses in quick succession is
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to read both of these values avoiding a second read delay is desirable.
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