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f8344f7693
TMP461 is almost identical to TMP451 and was actually detected as TMP451 with the existing lm90 driver if its I2C address is 0x4c. Add support for it to the lm90 driver. At the same time, improve the chip detection function to at least try to distinguish between TMP451 and TMP461. As a side effect, this fixes commit24333ac26d("hwmon: (tmp401) use smb word operations instead of 2 smb byte operations"). TMP461 does not support word operations on temperature registers, which causes bad temperature readings with the tmp401 driver. The lm90 driver does not perform word operations on temperature registers and thus does not have this problem. Support is listed as basic because TMP461 supports a sensor resolution of 0.0625 degrees C, while the lm90 driver assumes a resolution of 0.125 degrees C. Also, the TMP461 supports negative temperatures with its default temperature range, which is not the case for similar chips supported by the lm90 and the tmp401 drivers. Those limitations will be addressed with follow-up patches. Fixes:24333ac26d("hwmon: (tmp401) use smb word operations instead of 2 smb byte operations") Reported-by: David T. Wilson <david.wilson@nasa.gov> Cc: David T. Wilson <david.wilson@nasa.gov> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
428 lines
11 KiB
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428 lines
11 KiB
ReStructuredText
Kernel driver lm90
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==================
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Supported chips:
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* National Semiconductor LM90
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Prefix: 'lm90'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at the National Semiconductor website
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http://www.national.com/pf/LM/LM90.html
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* National Semiconductor LM89
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Prefix: 'lm89' (no auto-detection)
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Addresses scanned: I2C 0x4c and 0x4d
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Datasheet: Publicly available at the National Semiconductor website
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http://www.national.com/mpf/LM/LM89.html
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* National Semiconductor LM99
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Prefix: 'lm99'
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Addresses scanned: I2C 0x4c and 0x4d
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Datasheet: Publicly available at the National Semiconductor website
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http://www.national.com/pf/LM/LM99.html
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* National Semiconductor LM86
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Prefix: 'lm86'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at the National Semiconductor website
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http://www.national.com/mpf/LM/LM86.html
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* Analog Devices ADM1032
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Prefix: 'adm1032'
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Addresses scanned: I2C 0x4c and 0x4d
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Datasheet: Publicly available at the ON Semiconductor website
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https://www.onsemi.com/PowerSolutions/product.do?id=ADM1032
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* Analog Devices ADT7461
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Prefix: 'adt7461'
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Addresses scanned: I2C 0x4c and 0x4d
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Datasheet: Publicly available at the ON Semiconductor website
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https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461
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* Analog Devices ADT7461A
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Prefix: 'adt7461a'
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Addresses scanned: I2C 0x4c and 0x4d
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Datasheet: Publicly available at the ON Semiconductor website
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https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461A
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* ON Semiconductor NCT1008
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Prefix: 'nct1008'
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Addresses scanned: I2C 0x4c and 0x4d
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Datasheet: Publicly available at the ON Semiconductor website
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https://www.onsemi.com/PowerSolutions/product.do?id=NCT1008
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* Maxim MAX6646
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Prefix: 'max6646'
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Addresses scanned: I2C 0x4d
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
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* Maxim MAX6647
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Prefix: 'max6646'
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Addresses scanned: I2C 0x4e
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
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* Maxim MAX6648
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Prefix: 'max6646'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
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* Maxim MAX6649
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Prefix: 'max6646'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
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* Maxim MAX6654
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Prefix: 'max6654'
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Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
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0x4c, 0x4d and 0x4e
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Datasheet: Publicly available at the Maxim website
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https://www.maximintegrated.com/en/products/sensors/MAX6654.html
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* Maxim MAX6657
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Prefix: 'max6657'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
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* Maxim MAX6658
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Prefix: 'max6657'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
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* Maxim MAX6659
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Prefix: 'max6659'
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Addresses scanned: I2C 0x4c, 0x4d, 0x4e
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
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* Maxim MAX6680
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Prefix: 'max6680'
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Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
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0x4c, 0x4d and 0x4e
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
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* Maxim MAX6681
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Prefix: 'max6680'
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Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
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0x4c, 0x4d and 0x4e
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
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* Maxim MAX6692
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Prefix: 'max6646'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
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* Maxim MAX6695
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Prefix: 'max6695'
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Addresses scanned: I2C 0x18
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/datasheet/index.mvp/id/4199
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* Maxim MAX6696
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Prefix: 'max6695'
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Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
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0x4c, 0x4d and 0x4e
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Datasheet: Publicly available at the Maxim website
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http://www.maxim-ic.com/datasheet/index.mvp/id/4199
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* Winbond/Nuvoton W83L771W/G
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Prefix: 'w83l771'
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Addresses scanned: I2C 0x4c
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Datasheet: No longer available
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* Winbond/Nuvoton W83L771AWG/ASG
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Prefix: 'w83l771'
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Addresses scanned: I2C 0x4c
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Datasheet: Not publicly available, can be requested from Nuvoton
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* Philips/NXP SA56004X
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Prefix: 'sa56004'
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Addresses scanned: I2C 0x48 through 0x4F
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Datasheet: Publicly available at NXP website
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http://ics.nxp.com/products/interface/datasheet/sa56004x.pdf
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* GMT G781
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Prefix: 'g781'
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Addresses scanned: I2C 0x4c, 0x4d
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Datasheet: Not publicly available from GMT
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* Texas Instruments TMP451
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Prefix: 'tmp451'
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Addresses scanned: I2C 0x4c
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Datasheet: Publicly available at TI website
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https://www.ti.com/litv/pdf/sbos686
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* Texas Instruments TMP461
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Prefix: 'tmp461'
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Addresses scanned: I2C 0x48 through 0x4F
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Datasheet: Publicly available at TI website
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https://www.ti.com/lit/gpn/tmp461
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Author: Jean Delvare <jdelvare@suse.de>
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Description
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-----------
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The LM90 is a digital temperature sensor. It senses its own temperature as
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well as the temperature of up to one external diode. It is compatible
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with many other devices, many of which are supported by this driver.
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Note that there is no easy way to differentiate between the MAX6657,
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MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only
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supported by this driver if the chip is located at address 0x4d or 0x4e,
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or if the chip type is explicitly selected as max6659.
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The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously
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can't (and don't need to) be distinguished.
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The specificity of this family of chipsets over the ADM1021/LM84
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family is that it features critical limits with hysteresis, and an
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increased resolution of the remote temperature measurement.
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The different chipsets of the family are not strictly identical, although
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very similar. For reference, here comes a non-exhaustive list of specific
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features:
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LM90:
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* Filter and alert configuration register at 0xBF.
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* ALERT is triggered by temperatures over critical limits.
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LM86 and LM89:
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* Same as LM90
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* Better external channel accuracy
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LM99:
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* Same as LM89
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* External temperature shifted by 16 degrees down
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ADM1032:
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* Consecutive alert register at 0x22.
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* Conversion averaging.
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* Up to 64 conversions/s.
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* ALERT is triggered by open remote sensor.
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* SMBus PEC support for Write Byte and Receive Byte transactions.
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ADT7461, ADT7461A, NCT1008:
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* Extended temperature range (breaks compatibility)
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* Lower resolution for remote temperature
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MAX6654:
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* Better local resolution
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* Selectable address
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* Remote sensor type selection
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* Extended temperature range
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* Extended resolution only available when conversion rate <= 1 Hz
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MAX6657 and MAX6658:
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* Better local resolution
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* Remote sensor type selection
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MAX6659:
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* Better local resolution
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* Selectable address
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* Second critical temperature limit
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* Remote sensor type selection
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MAX6680 and MAX6681:
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* Selectable address
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* Remote sensor type selection
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MAX6695 and MAX6696:
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* Better local resolution
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* Selectable address (max6696)
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* Second critical temperature limit
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* Two remote sensors
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W83L771W/G
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* The G variant is lead-free, otherwise similar to the W.
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* Filter and alert configuration register at 0xBF
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* Moving average (depending on conversion rate)
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W83L771AWG/ASG
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* Successor of the W83L771W/G, same features.
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* The AWG and ASG variants only differ in package format.
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* Diode ideality factor configuration (remote sensor) at 0xE3
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SA56004X:
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* Better local resolution
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All temperature values are given in degrees Celsius. Resolution
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is 1.0 degree for the local temperature, 0.125 degree for the remote
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temperature, except for the MAX6654, MAX6657, MAX6658 and MAX6659 which have
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a resolution of 0.125 degree for both temperatures.
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Each sensor has its own high and low limits, plus a critical limit.
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Additionally, there is a relative hysteresis value common to both critical
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values. To make life easier to user-space applications, two absolute values
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are exported, one for each channel, but these values are of course linked.
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Only the local hysteresis can be set from user-space, and the same delta
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applies to the remote hysteresis.
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The lm90 driver will not update its values more frequently than configured with
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the update_interval attribute; reading them more often will do no harm, but will
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return 'old' values.
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SMBus Alert Support
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-------------------
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This driver has basic support for SMBus alert. When an alert is received,
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the status register is read and the faulty temperature channel is logged.
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The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON
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Semiconductor chips (NCT1008) do not implement the SMBus alert protocol
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properly so additional care is needed: the ALERT output is disabled when
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an alert is received, and is re-enabled only when the alarm is gone.
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Otherwise the chip would block alerts from other chips in the bus as long
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as the alarm is active.
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PEC Support
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-----------
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The ADM1032 is the only chip of the family which supports PEC. It does
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not support PEC on all transactions though, so some care must be taken.
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When reading a register value, the PEC byte is computed and sent by the
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ADM1032 chip. However, in the case of a combined transaction (SMBus Read
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Byte), the ADM1032 computes the CRC value over only the second half of
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the message rather than its entirety, because it thinks the first half
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of the message belongs to a different transaction. As a result, the CRC
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value differs from what the SMBus master expects, and all reads fail.
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For this reason, the lm90 driver will enable PEC for the ADM1032 only if
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the bus supports the SMBus Send Byte and Receive Byte transaction types.
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These transactions will be used to read register values, instead of
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SMBus Read Byte, and PEC will work properly.
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Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC.
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Instead, it will try to write the PEC value to the register (because the
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SMBus Send Byte transaction with PEC is similar to a Write Byte transaction
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without PEC), which is not what we want. Thus, PEC is explicitly disabled
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on SMBus Send Byte transactions in the lm90 driver.
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PEC on byte data transactions represents a significant increase in bandwidth
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usage (+33% for writes, +25% for reads) in normal conditions. With the need
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to use two SMBus transaction for reads, this overhead jumps to +50%. Worse,
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two transactions will typically mean twice as much delay waiting for
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transaction completion, effectively doubling the register cache refresh time.
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I guess reliability comes at a price, but it's quite expensive this time.
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So, as not everyone might enjoy the slowdown, PEC can be disabled through
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sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1
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to that file to enable PEC again.
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