Re: [9fans] sheevaplug SD card driver

[erik quanstrom <quanstro@quanstro.net>]

On Fri Oct 19 10:01:11 EDT 2012, 9fans@hamnavoe.com wrote:
> > could you explain the ccmalloc trick?
>
> "cache coherent malloc" - not really a trick, just a way to
> ensure SD buffers are cache-aligned and occupy an integral
> number of cache lines, to avoid embarrassment when doing
> dma on ARM (which bypasses the cache).  It costs a bit of
> space but saves copying.

that's what i thought.

we ran into this problem and decided that it was easiest to just
cacheline-align everything in malloc, at the obvious expense of
a tiny bit of memory.  the reason for this was we were using a few
kw devices that could get just about any chunk of malloc'd memory.

ideally we would have written a kw-specific malloc with tracking
segregated from the managed memory.

- erik