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hwmon: (jc42) optionally try to disable the SMBUS timeout

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commit 68615eb01f82256c19e41967bfb3eef902f77033 upstream.

With a nxp,se97 chip on an atmel sama5d31 board, the I2C adapter driver
is not always capable of avoiding the 25-35 ms timeout as specified by
the SMBUS protocol. This may cause silent corruption of the last bit of
any transfer, e.g. a one is read instead of a zero if the sensor chip
times out. This also affects the eeprom half of the nxp-se97 chip, where
this silent corruption was originally noticed. Other I2C adapters probably
suffer similar issues, e.g. bit-banging comes to mind as risky...

The SMBUS register in the nxp chip is not a standard Jedec register, but
it is not special to the nxp chips either, at least the atmel chips
have the same mechanism. Therefore, do not special case this on the
manufacturer, it is opt-in via the device property anyway.

Signed-off-by: Peter Rosin <peda@axentia.se>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Rosin
2017-11-27 17:31:00 +01:00
committed by Greg Kroah-Hartman
parent 8588eb0ce6
commit eafbee43b7
2 changed files with 25 additions and 0 deletions
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Documentation/devicetree/bindings/hwmon/jc42.txt
+4
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@@ -34,6 +34,10 @@ Required properties:
- reg: I2C address
Optional properties:
- smbus-timeout-disable: When set, the smbus timeout function will be disabled.
This is not supported on all chips.
Example:
temp-sensor@1a {