Re: [PATCH][RFC] asm-generic:remove calling flush_write_buffers() in dma_sync_*_for_cpu

[Ming Lei]

2009/7/7 Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>:
> On Tue, Jul 07, 2009 at 09:54:20AM +0800, Ming Lei wrote:
>> 2009/6/30 Arnd Bergmann <arnd@xxxxxxxx>:
>> > On Tuesday 30 June 2009, Alan Cox wrote:
>> > Well, not even that. dma-mapping-common.h only makes sense on architectures
>> > that have multiple dma-mapping implementations (parisc, mips, arm, powerpc,
>>
>> It seems that there is only one dma-mmaping implementation on ARM, doesn't it?
>> Is it necessary that using dma-mapping-common.h on ARM?
>
> ARM has two (normal, and dma bounce), and in the long run we need to do

OK, Can we use dma-mapping-common.h on ARM?

> cache handling on unmap as well as map due to CPU speculative fetches.

IMHO, it seems we can fix this problem now.

For DMA_TO_DEVICE transfer, clean cache in dma map, but does nothing in
dma unmap;

For  DMA_FROM_DEVICE, we may do nothing in dma map, but invaliate cache
in dma unmap.

Is it doable?

Thanks.
-- 
Lei Ming
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/