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On systems where the temperature sensor is actually used, the BIOS is likely to have locked the alarm registers. In that case, all writes through the corresponding sysfs files would be silently ignored. To prevent this, detect the locks and make the affected sysfs files read-only. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Cc: stable@kernel.org Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
107 lines
3.8 KiB
Plaintext
107 lines
3.8 KiB
Plaintext
Kernel driver jc42
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==================
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Supported chips:
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* Analog Devices ADT7408
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Prefix: 'adt7408'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheets:
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http://www.analog.com/static/imported-files/data_sheets/ADT7408.pdf
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* IDT TSE2002B3, TS3000B3
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Prefix: 'tse2002b3', 'ts3000b3'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheets:
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http://www.idt.com/products/getdoc.cfm?docid=18715691
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http://www.idt.com/products/getdoc.cfm?docid=18715692
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* Maxim MAX6604
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Prefix: 'max6604'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheets:
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http://datasheets.maxim-ic.com/en/ds/MAX6604.pdf
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* Microchip MCP9805, MCP98242, MCP98243, MCP9843
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Prefixes: 'mcp9805', 'mcp98242', 'mcp98243', 'mcp9843'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheets:
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http://ww1.microchip.com/downloads/en/DeviceDoc/21977b.pdf
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http://ww1.microchip.com/downloads/en/DeviceDoc/21996a.pdf
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http://ww1.microchip.com/downloads/en/DeviceDoc/22153c.pdf
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* NXP Semiconductors SE97, SE97B
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Prefix: 'se97'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheets:
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http://www.nxp.com/documents/data_sheet/SE97.pdf
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http://www.nxp.com/documents/data_sheet/SE97B.pdf
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* NXP Semiconductors SE98
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Prefix: 'se98'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheets:
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http://www.nxp.com/documents/data_sheet/SE98.pdf
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* ON Semiconductor CAT34TS02, CAT6095
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Prefix: 'cat34ts02', 'cat6095'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheet:
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http://www.onsemi.com/pub_link/Collateral/CAT34TS02-D.PDF
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http://www.onsemi.com/pub/Collateral/CAT6095-D.PDF
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* ST Microelectronics STTS424, STTS424E02
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Prefix: 'stts424'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheets:
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http://www.st.com/stonline/products/literature/ds/13447/stts424.pdf
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http://www.st.com/stonline/products/literature/ds/13448/stts424e02.pdf
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* JEDEC JC 42.4 compliant temperature sensor chips
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Prefix: 'jc42'
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Addresses scanned: I2C 0x18 - 0x1f
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Datasheet:
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http://www.jedec.org/sites/default/files/docs/4_01_04R19.pdf
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Author:
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Guenter Roeck <guenter.roeck@ericsson.com>
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Description
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-----------
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This driver implements support for JEDEC JC 42.4 compliant temperature sensors,
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which are used on many DDR3 memory modules for mobile devices and servers. Some
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systems use the sensor to prevent memory overheating by automatically throttling
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the memory controller.
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The driver auto-detects the chips listed above, but can be manually instantiated
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to support other JC 42.4 compliant chips.
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Example: the following will load the driver for a generic JC 42.4 compliant
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temperature sensor at address 0x18 on I2C bus #1:
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# modprobe jc42
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# echo jc42 0x18 > /sys/bus/i2c/devices/i2c-1/new_device
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A JC 42.4 compliant chip supports a single temperature sensor. Minimum, maximum,
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and critical temperature can be configured. There are alarms for high, low,
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and critical thresholds.
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There is also an hysteresis to control the thresholds for resetting alarms.
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Per JC 42.4 specification, the hysteresis threshold can be configured to 0, 1.5,
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3.0, and 6.0 degrees C. Configured hysteresis values will be rounded to those
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limits. The chip supports only a single register to configure the hysteresis,
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which applies to all limits. This register can be written by writing into
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temp1_crit_hyst. Other hysteresis attributes are read-only.
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If the BIOS has configured the sensor for automatic temperature management, it
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is likely that it has locked the registers, i.e., that the temperature limits
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cannot be changed.
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Sysfs entries
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-------------
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temp1_input Temperature (RO)
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temp1_min Minimum temperature (RO or RW)
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temp1_max Maximum temperature (RO or RW)
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temp1_crit Critical high temperature (RO or RW)
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temp1_crit_hyst Critical hysteresis temperature (RO or RW)
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temp1_max_hyst Maximum hysteresis temperature (RO)
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temp1_min_alarm Temperature low alarm
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temp1_max_alarm Temperature high alarm
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temp1_crit_alarm Temperature critical alarm
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