[openib-general] [PATCH 0/7] AMSO1100 RNIC Driver

[Roland Dreier]

I just realized that the amso1100 driver probably won't work on a
big-endian architecture.  This is actually because your hardware is
itself big-endian, so you end up doing stuff like

    writel(cpu_to_be32(foo), bar);

in a lot of places.  Unfortunately, writel() operates with the assumption
that the PCI bus is little-endian.  In other words, on x86, your writel()
essentially becomes (because cpu_to_be32 is a swap):

    *bar = swab32(foo);

but on big-endian archs like powerpc, a byte-swap is performed by writel()
so you still end up doing something like the following (even though
cpu_to_be32 is a no-op on big-endian archs):

    *bar = swab32(foo);

which is wrong when foo is already big-endian.

There's not really a great solution to this.  The best I've come up with
is to use __raw_writel() instead, but then you have to be careful, because
in addition to not byte swapping, the __raw variants also don't have any
implied barriers, so you need to add your own wmb()s.

You can see some examples of this in mthca, for example in the FW
command stuff in mthca_cmd.c.

 - R.