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From: "Russell McGuire" <rmcguire@videopresence.com>
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References: <mailman.1.1220580004.22796.linuxppc-embedded@ozlabs.org>
Subject: 1MB alignment dma_alloc question
Date: Fri, 5 Sep 2008 14:11:31 -0700
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Anyone,

Putting together a driver, IMA for ATM in a MPC83xx. Anyway the manual
states that one of the data structures for the QE needs to be allocated on a
1MB boundary in external memory.

Normally these come in 128/64/32byte boundaries and are easy to self align,
with some bit logic. However, after reading up on dma_alloc_coherent I see
that a limitation is that dma cannot span 64K page boundaries.

So this begs a question is their a better way to get a 1MB aligned table?
Other than allocating almost 2MB of memory and then trying to mask off the
LSBs? Seems like an awful waste of memory. I guess the real question is
there a better kernel call that returns already aligned DMA memory?

Thanks,

-Russ