tree b4dc6bc55f6961e004dbf93e6a2ce820be41b3a9
parent 616228a164d4366f82d983c4a70d8006d9fb43f2
author Marek Vasut <marex@denx.de> 1381060933 +0200
committer Wolfram Sang <wsa@the-dreams.de> 1381067786 +0200

i2c: mxs: Rework the PIO mode operation

Analyze and rework the PIO mode operation. The PIO mode operation
was unreliable on MX28, by analyzing the bus with LA, the checks
for when data were available or were to be sent were wrong.

The PIO WRITE has to be completely reworked as it multiple problems.
The MX23 datasheet helped here, see comments in the code for details.
The problems boil down to:
- RUN bit in CTRL0 must be set after DATA register was written
- The PIO transfer must be 4 bytes long tops, otherwise use
  clock stretching.
Both of these fixes are implemented.

The PIO READ operation can only be done for up to four bytes as
we are unable to read out the data from the DATA register fast
enough.

This patch also tries to document the investigation within the
code.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>