Re: Question about porting VxWorks driver

[Vladimir Gurevich <vag@paulidav.org>]

Hello Donald,

Is it one of Hifn chips by any chance? If yes, then I can
tell you that their drivers do not know about cache flushes
and invalidates at all, which presents a real challenge on
PowerPC.

Writeback cache usually won't work. You have to manually
flush it before sending a message to the board and invalidate
it after you receive the encrypted (decrypted) message back.
If you do the transformation "in-place" then you can use
flush-and-invalidate before seding the message. Using uncached
memory is another option, but if you want to do further
processing without copying data to a cached buffer, you
performance will likely suffer.

In general you keep data buffers in cached memory and
do manual flushes/invalidates when needed, but keep
buffer descriptors and other similar structures (as
well as chip's registers and chip's private memory)
in uncached space.

Best regards,
Vladimir


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