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Diffstat (limited to 'kernel/Documentation/hwmon/lm90')
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diff --git a/kernel/Documentation/hwmon/lm90 b/kernel/Documentation/hwmon/lm90 new file mode 100644 index 000000000..8122675d3 --- /dev/null +++ b/kernel/Documentation/hwmon/lm90 @@ -0,0 +1,275 @@ +Kernel driver lm90 +================== + +Supported chips: + * National Semiconductor LM90 + Prefix: 'lm90' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at the National Semiconductor website + http://www.national.com/pf/LM/LM90.html + * National Semiconductor LM89 + Prefix: 'lm89' (no auto-detection) + Addresses scanned: I2C 0x4c and 0x4d + Datasheet: Publicly available at the National Semiconductor website + http://www.national.com/mpf/LM/LM89.html + * National Semiconductor LM99 + Prefix: 'lm99' + Addresses scanned: I2C 0x4c and 0x4d + Datasheet: Publicly available at the National Semiconductor website + http://www.national.com/pf/LM/LM99.html + * National Semiconductor LM86 + Prefix: 'lm86' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at the National Semiconductor website + http://www.national.com/mpf/LM/LM86.html + * Analog Devices ADM1032 + Prefix: 'adm1032' + Addresses scanned: I2C 0x4c and 0x4d + Datasheet: Publicly available at the ON Semiconductor website + http://www.onsemi.com/PowerSolutions/product.do?id=ADM1032 + * Analog Devices ADT7461 + Prefix: 'adt7461' + Addresses scanned: I2C 0x4c and 0x4d + Datasheet: Publicly available at the ON Semiconductor website + http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461 + * Analog Devices ADT7461A + Prefix: 'adt7461a' + Addresses scanned: I2C 0x4c and 0x4d + Datasheet: Publicly available at the ON Semiconductor website + http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461A + * ON Semiconductor NCT1008 + Prefix: 'nct1008' + Addresses scanned: I2C 0x4c and 0x4d + Datasheet: Publicly available at the ON Semiconductor website + http://www.onsemi.com/PowerSolutions/product.do?id=NCT1008 + * Maxim MAX6646 + Prefix: 'max6646' + Addresses scanned: I2C 0x4d + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497 + * Maxim MAX6647 + Prefix: 'max6646' + Addresses scanned: I2C 0x4e + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497 + * Maxim MAX6648 + Prefix: 'max6646' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500 + * Maxim MAX6649 + Prefix: 'max6646' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497 + * Maxim MAX6657 + Prefix: 'max6657' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578 + * Maxim MAX6658 + Prefix: 'max6657' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578 + * Maxim MAX6659 + Prefix: 'max6659' + Addresses scanned: I2C 0x4c, 0x4d, 0x4e + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578 + * Maxim MAX6680 + Prefix: 'max6680' + Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, + 0x4c, 0x4d and 0x4e + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370 + * Maxim MAX6681 + Prefix: 'max6680' + Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, + 0x4c, 0x4d and 0x4e + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370 + * Maxim MAX6692 + Prefix: 'max6646' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500 + * Maxim MAX6695 + Prefix: 'max6695' + Addresses scanned: I2C 0x18 + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/datasheet/index.mvp/id/4199 + * Maxim MAX6696 + Prefix: 'max6695' + Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, + 0x4c, 0x4d and 0x4e + Datasheet: Publicly available at the Maxim website + http://www.maxim-ic.com/datasheet/index.mvp/id/4199 + * Winbond/Nuvoton W83L771W/G + Prefix: 'w83l771' + Addresses scanned: I2C 0x4c + Datasheet: No longer available + * Winbond/Nuvoton W83L771AWG/ASG + Prefix: 'w83l771' + Addresses scanned: I2C 0x4c + Datasheet: Not publicly available, can be requested from Nuvoton + * Philips/NXP SA56004X + Prefix: 'sa56004' + Addresses scanned: I2C 0x48 through 0x4F + Datasheet: Publicly available at NXP website + http://ics.nxp.com/products/interface/datasheet/sa56004x.pdf + * GMT G781 + Prefix: 'g781' + Addresses scanned: I2C 0x4c, 0x4d + Datasheet: Not publicly available from GMT + * Texas Instruments TMP451 + Prefix: 'tmp451' + Addresses scanned: I2C 0x4c + Datasheet: Publicly available at TI website + http://www.ti.com/litv/pdf/sbos686 + + +Author: Jean Delvare <jdelvare@suse.de> + + +Description +----------- + +The LM90 is a digital temperature sensor. It senses its own temperature as +well as the temperature of up to one external diode. It is compatible +with many other devices, many of which are supported by this driver. + +Note that there is no easy way to differentiate between the MAX6657, +MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only +supported by this driver if the chip is located at address 0x4d or 0x4e, +or if the chip type is explicitly selected as max6659. +The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously +can't (and don't need to) be distinguished. + +The specificity of this family of chipsets over the ADM1021/LM84 +family is that it features critical limits with hysteresis, and an +increased resolution of the remote temperature measurement. + +The different chipsets of the family are not strictly identical, although +very similar. For reference, here comes a non-exhaustive list of specific +features: + +LM90: + * Filter and alert configuration register at 0xBF. + * ALERT is triggered by temperatures over critical limits. + +LM86 and LM89: + * Same as LM90 + * Better external channel accuracy + +LM99: + * Same as LM89 + * External temperature shifted by 16 degrees down + +ADM1032: + * Consecutive alert register at 0x22. + * Conversion averaging. + * Up to 64 conversions/s. + * ALERT is triggered by open remote sensor. + * SMBus PEC support for Write Byte and Receive Byte transactions. + +ADT7461, ADT7461A, NCT1008: + * Extended temperature range (breaks compatibility) + * Lower resolution for remote temperature + +MAX6657 and MAX6658: + * Better local resolution + * Remote sensor type selection + +MAX6659: + * Better local resolution + * Selectable address + * Second critical temperature limit + * Remote sensor type selection + +MAX6680 and MAX6681: + * Selectable address + * Remote sensor type selection + +MAX6695 and MAX6696: + * Better local resolution + * Selectable address (max6696) + * Second critical temperature limit + * Two remote sensors + +W83L771W/G + * The G variant is lead-free, otherwise similar to the W. + * Filter and alert configuration register at 0xBF + * Moving average (depending on conversion rate) + +W83L771AWG/ASG + * Successor of the W83L771W/G, same features. + * The AWG and ASG variants only differ in package format. + * Diode ideality factor configuration (remote sensor) at 0xE3 + +SA56004X: + * Better local resolution + +All temperature values are given in degrees Celsius. Resolution +is 1.0 degree for the local temperature, 0.125 degree for the remote +temperature, except for the MAX6657, MAX6658 and MAX6659 which have a +resolution of 0.125 degree for both temperatures. + +Each sensor has its own high and low limits, plus a critical limit. +Additionally, there is a relative hysteresis value common to both critical +values. To make life easier to user-space applications, two absolute values +are exported, one for each channel, but these values are of course linked. +Only the local hysteresis can be set from user-space, and the same delta +applies to the remote hysteresis. + +The lm90 driver will not update its values more frequently than configured with +the update_interval attribute; reading them more often will do no harm, but will +return 'old' values. + +SMBus Alert Support +------------------- + +This driver has basic support for SMBus alert. When an alert is received, +the status register is read and the faulty temperature channel is logged. + +The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON +Semiconductor chips (NCT1008) do not implement the SMBus alert protocol +properly so additional care is needed: the ALERT output is disabled when +an alert is received, and is re-enabled only when the alarm is gone. +Otherwise the chip would block alerts from other chips in the bus as long +as the alarm is active. + +PEC Support +----------- + +The ADM1032 is the only chip of the family which supports PEC. It does +not support PEC on all transactions though, so some care must be taken. + +When reading a register value, the PEC byte is computed and sent by the +ADM1032 chip. However, in the case of a combined transaction (SMBus Read +Byte), the ADM1032 computes the CRC value over only the second half of +the message rather than its entirety, because it thinks the first half +of the message belongs to a different transaction. As a result, the CRC +value differs from what the SMBus master expects, and all reads fail. + +For this reason, the lm90 driver will enable PEC for the ADM1032 only if +the bus supports the SMBus Send Byte and Receive Byte transaction types. +These transactions will be used to read register values, instead of +SMBus Read Byte, and PEC will work properly. + +Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC. +Instead, it will try to write the PEC value to the register (because the +SMBus Send Byte transaction with PEC is similar to a Write Byte transaction +without PEC), which is not what we want. Thus, PEC is explicitly disabled +on SMBus Send Byte transactions in the lm90 driver. + +PEC on byte data transactions represents a significant increase in bandwidth +usage (+33% for writes, +25% for reads) in normal conditions. With the need +to use two SMBus transaction for reads, this overhead jumps to +50%. Worse, +two transactions will typically mean twice as much delay waiting for +transaction completion, effectively doubling the register cache refresh time. +I guess reliability comes at a price, but it's quite expensive this time. + +So, as not everyone might enjoy the slowdown, PEC can be disabled through +sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1 +to that file to enable PEC again. |