Re: [RFC PATCH] dma: Add barrierless dma mapping/unmapping api

From: Abhijeet Dharmapurikar
Date: Tue Jan 26 2010 - 15:11:45 EST

FUJITA Tomonori wrote:
On Tue, 26 Jan 2010 15:30:10 +1100
Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote:

On Mon, 2010-01-25 at 18:35 -0800, adharmap@xxxxxxxxxxxxxx wrote:
From: Abhijeet Dharmapurikar <adharmap@xxxxxxxxxxx>

There are people nowadays putting AXI bridges and the whole ARM
paraphernalia of IP cores behind them on PowerPC cores for example and I
can see that happening with x86 as well.

In your case, I believe your are fixing the wrong problem anyways. The
right approach would be instead to put all your buffer into an sglist
and use dma_map/unmap_sg().

Agreed again. That's exactly what I suggested before:

I somehow missed your post, my apologies. Agreed that dma_map/unmap_sg would be the correct api to use here, however they still call the dmac_.*_range to map buffers. I could change those calls to do a barrier only after mapping the last buffer. This would be much more cleaner than introducing a .*_nobarrier API.

Thanks for all the replies.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at