[PATCH v6] spi: orion.c: Add direct access mode

[Stefan Roese]

On 20.04.2016 12:11, Stefan Roese wrote:
> This patch adds support for the direct write mode to the Orion SPI
> driver which is used on the Marvell Armada based SoCs. In this direct
> mode, all data written to (or read from) a specifically mapped MBus
> window (linked to one SPI chip-select on one of the SPI controllers)
> will be transferred directly to the SPI bus. Without the need to control
> the SPI registers in between. This can improve the SPI transfer rate in
> such cases.
> 
> Currently only the direct write mode is supported. This mode especially
> benefits from the SPI direct mode, as the data bytes are written
> head-to-head to the SPI bus, without any additional addresses, that
> are also written in the direct read mode.
> 
> One use-case for this direct write mode is, programming a FPGA bitstream
> image into the FPGA connected to the SPI bus at maximum speed.
> 
> This mode is described in chapter "22.5.2 Direct Write to SPI" in the
> Marvell Armada XP Functional Spec Datasheet.
> 
> It should be possible to support SPI-NOR and SPI-NAND devices via
> this direct access mode as well. But this needs further work, e.g.:
> - The mapping of the MBus window needs to get extended to span
>    the complete flash device size
> - The address / control data needs to get inserted into the SPI
>    controller registers
> 
> Signed-off-by: Stefan Roese <sr at denx.de>
> Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
> Cc: Gregory CLEMENT <gregory.clement at free-electrons.com>
> Cc: Andrew Lunn <andrew at lunn.ch>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Cc: Mark Brown <broonie at kernel.org>

Its been a while since v6 of this direct write access mode has been
posted. This is a gentle ping on its status.

Arnd / Mark, do you have any additional change requests or are you okay
with the current version?

Thanks,
Stefan