spi: Add support for preamble bytes
authorRajeshwari Shinde <rajeshwari.s@samsung.com>
Tue, 28 May 2013 20:10:37 +0000 (20:10 +0000)
committerJagannadha Sutradharudu Teki <jaganna@xilinx.com>
Sun, 2 Jun 2013 18:34:40 +0000 (00:04 +0530)
commitbb786b84bdbcfe0474d53a54c82c5695494a6ab5
treec329b3cc06a64f9312ac988d48305b89af8056ae
parented03f41778c7a11adf81816278c92dfae23d6d77
spi: Add support for preamble bytes

A SPI slave may take time to react to a request. For SPI flash devices
this time is defined as one bit time, or a whole byte for 'fast read'
mode.

If the SPI slave is another CPU, then the time it takes to react may
vary. It is convenient to allow the slave device to tag the start of
the actual reply so that the host can determine when this 'preamble'
finishes and the actual message starts.

Add a preamble flag to the available SPI flags. If supported by the
driver then it will ignore any received bytes before the preamble
on each transaction. This ensures that reliable communication with
the slave is possible.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
include/spi.h