Prefix: 'lm99'
Addresses scanned: I2C 0x4c and 0x4d
Datasheet: Publicly available at the National Semiconductor website
- http://www.national.com/pf/LM/LM89.html
+ http://www.national.com/mpf/LM/LM89.html
* National Semiconductor LM99
Prefix: 'lm99'
Addresses scanned: I2C 0x4c and 0x4d
Prefix: 'lm86'
Addresses scanned: I2C 0x4c
Datasheet: Publicly available at the National Semiconductor website
- http://www.national.com/pf/LM/LM86.html
+ http://www.national.com/mpf/LM/LM86.html
* Analog Devices ADM1032
Prefix: 'adm1032'
- Addresses scanned: I2C 0x4c
- Datasheet: Publicly available at the Analog Devices website
- http://products.analog.com/products/info.asp?product=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
+ * 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 MAX6649
+ Prefix: 'max6646'
Addresses scanned: I2C 0x4c
- Datasheet: Publicly available at the Analog Devices website
- http://products.analog.com/products/info.asp?product=ADT7461
- Note: Only if in ADM1032 compatibility mode
+ 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
Addresses scanned: I2C 0x4c, 0x4d (unsupported 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
Author: Jean Delvare <khali@linux-fr.org>
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 such as the LM86, the LM89, the LM99, the ADM1032,
-the MAX6657, MAX6658 and the MAX6659 all of which are supported by this driver.
-Note that there is no easy way to differentiate between the last three
-variants. The extra address and features of the MAX6659 are not supported by
-this driver. Additionally, the ADT7461 is supported if found in ADM1032
-compatibility mode.
+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 address and features of the
+MAX6659 are not supported by this driver. 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. This driver doesn't handle any specific feature for now,
-but could if there ever was a need for it. For reference, here comes a
-non-exhaustive list of specific features:
+very similar. For reference, here comes a non-exhaustive list of specific
+features:
LM90:
* Filter and alert configuration register at 0xBF.
* 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
+ADT7461:
* Extended temperature range (breaks compatibility)
* Lower resolution for remote temperature
MAX6657 and MAX6658:
+ * Better local resolution
* Remote sensor type selection
-MAX6659
+MAX6659:
+ * Better local resolution
* Selectable address
* Second critical temperature limit
* Remote sensor type selection
+MAX6680 and MAX6681:
+ * Selectable address
+ * Remote sensor type selection
+
All temperature values are given in degrees Celsius. Resolution
is 1.0 degree for the local temperature, 0.125 degree for the remote
-temperature.
+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
other second; reading them more often will do no harm, but will return
'old' values.
+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.
projects / linux-2.6-omap-h63xx.git / blobdiff