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SubjectRE: [PATCH 1/2 v3] dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller
Nicolas Ferre wrote:
> Dan Williams :
>> On Fri, Jul 3, 2009 at 10:24 AM, Nicolas Ferre<> wrote:
>>> This AHB DMA Controller (aka HDMA or DMAC on AT91 systems) is availlable on
>>> at91sam9rl chip. It will be used on other products in the future.
>>> This first release covers only the memory-to-memory tranfer type. This is the
>>> only tranfer type supported by this chip. On other products, it will be used
>>> also for peripheral DMA transfer (slave API support to come).
>>> I used dmatest client without problem in different configurations to test it.
>>> Full documentation for this controller can be found in the SAM9RL datasheet:
>>> Signed-off-by: Nicolas Ferre <> ---
>>> v2 is here:
>>> v2 -> v3:
>>> - initial number of descriptors to allocate for each channel raised to 64 and is now a
>>> parameter
>>> - ack-bit in descriptor flag comment synchronized with TXx9 dma driver
>>> - atc_desc_get() when short on descriptors in pool: create one at a time
>>> - allocation flag changed to GFP_ATOMIC in atc_desc_get()
>>> - call to proper funtion while unmapping: use of new
>>> - call dma_run_dependencies() at the end of atc_chain_complete()
>> Looks good, but now I belatedly wonder if that GFP_ATOMIC should be
>> GFP_NOWAIT instead? Do we really want to consume from the system
>> emergency pools for these allocations (a similar fix is need for
>> ioatdma and fsldma)?
> Seems sensible indeed but I know little about allocation flags.
> What do you think about including the driver and then building a patch
> that fixes this flag in all allocation functions at a time.
> It may add exposure to this modification and maybe encourage people to
> react...

I think it's a good plan.
I will prepare similar patch on allocation flags for ioatdma.

For this v3 patch:

Acked-by: Maciej Sosnowski <>


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