Change the nx-842 common driver to wait for loading of both platform
drivers, and fail loading if the platform driver pointer is not set.
Add an independent platform driver pointer, that the platform drivers
set if they find they are able to load (i.e. if they find their platform
devicetree node(s)).

The problem is currently, the main nx-842 driver will stay loaded even
if there is no platform driver and thus no possible way it can do any
compression or decompression.  This allows the crypto 842-nx driver
to load even if it won't actually work.  For crypto compression users
(e.g. zswap) that expect an available crypto compression driver to
actually work, this is bad.  This patch fixes that, so the 842-nx crypto
compression driver won't load if it doesn't have the driver and hardware
available to perform the compression.
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add driver for NX-842 hardware on the PowerNV platform.

This allows the use of the 842 compression hardware coprocessor on
the PowerNV platform.
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add "constraints" for the NX-842 driver.  The constraints are used to
indicate what the current NX-842 platform driver is capable of.  The
constraints tell the NX-842 user what alignment, min and max length, and
length multiple each provided buffers should conform to.  These are
required because the 842 hardware requires buffers to meet specific
constraints that vary based on platform - for example, the pSeries
max length is much lower than the PowerNV max length.
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add NX-842 frontend that allows using either the pSeries platform or
PowerNV platform driver (to be added by later patch) for the NX-842
hardware.  Update the MAINTAINERS file to include the new filenames.
Update Kconfig files to clarify titles and descriptions, and correct
dependencies.
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>