Simon Glass 34bba87577 snow: Implement I2C arbitration ...

Use two suitable GPIOs to implement a simple arbitration scheme.
Each side owns one of the GPIOs, which are normally pulled high.
When one side wants to use I2C as a master, it pulls its GPIO low,
waits for a short period to make sure that the other side is not
also pulling its GPIO low, and then goes ahead with the transaction.

When the transaction is over, the GPIO is released, thus freeing the
I2C bus up for use by the other end.

For simplicity the terminolgy used here is EC for us, and AP for the
other end.

BUG=chrome-os-partner:10888
TEST=manual:
build for all boards
boot on snow (cannot test i2c as it is broken)

Change-Id: I97d9fbd5aba8248c8c1240baaec17db22860665c
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/26142

2012-07-02 22:35:50 -07:00

..

bds

Only one RW image is now the default

2012-06-26 13:58:54 -07:00

daisy

stm32: Use SPI ports for i2c arbitration

2012-06-28 11:56:30 -07:00

link

Only one RW image is now the default

2012-06-26 13:58:54 -07:00

snow

snow: Implement I2C arbitration

2012-07-02 22:35:50 -07:00