Re: [PATCH RFC 2/2] ARM: pxa: transition to dmaengine phase 1

From: Robert Jarzmik
Date: Mon Feb 16 2015 - 11:54:27 EST

Vasily Khoruzhick <anarsoul@xxxxxxxxx> writes:

> On Sun, Feb 15, 2015 at 1:47 AM, Robert Jarzmik <robert.jarzmik@xxxxxxx> wrote:
>> In order to slowly transition pxa to dmaengine, the legacy code will now
>> rely on dmaengine to request a channel.
> Hi Robert,
> What about dropping old PXA DMA code completely? Daniel Mack did port
> for most of PXA drivers to dma engine,
> I've rebased his patches against 3.17 several months ago and fixed
> oopses in pxamci and asoc drivers, but I didn't resubmit whole series
> due to lack of time.

Well, it's the last step, yes.
But I want a "smooth transition" : if amongst the ported drivers one starts to
bug, I want to be able to revert _only_ that driver port to dmaengine, and not
_all_ the drivers.

That's the rationale of this patch :
- phase 1 : enable peacefull coexistence of legacy pxa_request_dma() and
dmaengine for pxa, for both devicetree and legacy platforms
- phase 2 : port the drivers, and ensure the work correctly
This might take a couple of cycles
Note that phase 1 ensures that submissions can go through each
maintainer's tree without need for strong consistence.
- phase 3 : revert the mmp_pdma patch, and drop arch/arm/plat-pxa/dma.c

> My 3.17 tree is at [1], I've tested it on pxa270 machine (Zipit Z2),
> and everything works fine so far. I guess it won't be too much work to
> rebase it against linux-3.20.
Oh, do you volunteer ? That would indeed ease up my burden. I only rebased
pxa3xx_nand, so any help to submit and push is welcome. At least I can commit to
review, and I would concentrate on pxa_camera.c in the meantime.


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