[PATCH 2/2] dma: mv_xor: do not sync the DMA buffer after being deallocated

On Fri, 2013-01-04 at 17:10 +0100, Thomas Petazzoni wrote:

Dear Lubomir Rintel,

On Thu, 27 Dec 2012 20:23:48 +0100, Lubomir Rintel wrote:

quoted

 	dma_sync_single_for_cpu(dma_chan->device->dev, dest_dma,
 				MV_XOR_TEST_SIZE, DMA_FROM_DEVICE);
+	dma_unmap_single(dma_chan->device->dev, dest_dma, MV_XOR_TEST_SIZE,
+			 DMA_FROM_DEVICE);

I would assume that dma_unmap_single() implies a
dma_sync_single_for_cpu() since you're unmapping the DMA buffer. So if
you use dma_unmap_single(), I think you can remove the call to
dma_sync_single_for_cpu().

Yes, it indeed seems to be the case (comment for arm_dma_unmap_page():
"After this call, reads by the CPU to the buffer are guaranteed to see
whatever the device wrote there.".

quoted

 	dma_sync_single_for_cpu(dma_chan->device->dev, dest_dma,
 				PAGE_SIZE, DMA_FROM_DEVICE);
+	dma_unmap_page(dma_chan->device->dev, dest_dma, PAGE_SIZE,
+		       DMA_FROM_DEVICE);

Ditto.

Also, the mv_xor_memcpy_self_test() function not only dma_map_single()
the destination buffer, but also the source buffer. So presumably, the
source buffer should also be dma_unmap_single()'d.

And for the mv_xor_xor_self_test() function, multiple source buffers
are dma_map_page()'d, so they should all be dma_unmap_page()'d I guess,
not only the destination buffer.

Those get released by the mv_xor_run_tx_complete_actions() callback.

I will follow up with an updated patch.

Regards,
Lubo