i2c: Adding support for Intel iSMT SMBus 2.0 host controller

The iSMT (Intel SMBus Message Transport) supports multi-master I2C/SMBus,
as well as IPMI.  It's operation is DMA-based and utilizes descriptors to
initiate transactions on the bus.

The iSMT hardware can act as both a master and a target, although this
driver only supports being a master.

Signed-off-by: Neil Horman <[email protected]>
Signed-off-by: Bill Brown <[email protected]>
Tested-by: Seth Heasley <[email protected]>
Reviewed-by: Jean Delvare <[email protected]>
Signed-off-by: Wolfram Sang <[email protected]>

Documentation/i2c/busses/i2c-ismt

@@ -0,0 +1,36 @@
+Kernel driver i2c-ismt
+
+Supported adapters:
+  * Intel S12xx series SOCs
+
+Authors:
+	Bill Brown <[email protected]>
+
+
+Module Parameters
+-----------------
+
+* bus_speed (unsigned int)
+Allows changing of the bus speed.  Normally, the bus speed is set by the BIOS
+and never needs to be changed.  However, some SMBus analyzers are too slow for
+monitoring the bus during debug, thus the need for this module parameter.
+Specify the bus speed in kHz.
+Available bus frequency settings:
+  0  no change
+  80 kHz
+  100 kHz
+  400 kHz
+  1000 kHz
+
+
+Description
+-----------
+
+The S12xx series of SOCs have a pair of integrated SMBus 2.0 controllers
+targeted primarily at the microserver and storage markets.
+
+The S12xx series contain a pair of PCI functions.  An output of lspci will show
+something similar to the following:
+
+  00:13.0 System peripheral: Intel Corporation Centerton SMBus 2.0 Controller 0
+  00:13.1 System peripheral: Intel Corporation Centerton SMBus 2.0 Controller 1