tree 3288418e64b59594729bdd049bff06120dfc6a64
parent bb336ba0aaa5bef253d60bdeb08537ddecc7f42f
author Boris BREZILLON <boris.brezillon@free-electrons.com> 1402478250 +0200
committer Wolfram Sang <wsa@the-dreams.de> 1402525446 +0200

i2c: sunxi: add P2WI (Push/Pull 2 Wire Interface) controller support

The P2WI controller looks like an SMBus controller which only supports byte
data transfers. But, it differs from standard SMBus protocol on several
aspects:
- it supports only one slave device, and thus drop the address field
- it adds a parity bit every 8bits of data
- only one read access is required to read a byte (instead of a write
  followed by a read access in standard SMBus protocol)
- there's no Ack bit after each byte transfer

This means this bus cannot be used to interface with standard SMBus
devices (the only known device to support this interface is the AXP221
PMIC).
However the P2WI protocol is close enough to SMBus to be integrated in
the I2C subsystem (see this thread [1] for detailed reasons that led to
integrating this driver in the I2C subsystem).

[1] http://www.spinics.net/lists/linux-i2c/msg15066.html

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>