PL-330 DMA driver

[Ben Dooks]

On Thu, Feb 18, 2010 at 10:32:03AM +0000, Russell King - ARM Linux wrote:
> On Wed, Feb 17, 2010 at 11:24:28PM -0700, Dan Williams wrote:
> > On Tue, Feb 16, 2010 at 10:50 PM, jassi brar <jassisinghbrar at gmail.com> wrote:
> > > Hello,
> > >
> > >  Many Samsung SoCs have PL-330 as the DMA controller and the driver
> > > is missing in the mainline.
> > >
> > > A few months ago, Joonyoung Shim of Samsung, attempted the driver for PL-330
> > > based on the DMA API(drivers/dma/), but the patches weren't accepted.
> > 
> > Looking back at the archives seems I missed this patch.  So it was not
> > rejected just overlooked.  Do we want to move forward on that patch as
> > it stands, or go a different direction?  If it is resubmitted I will
> > get it in the queue for 2.6.34.
> 
> If it's a generic ARM primecell, it's likely it will be used elsewhere as
> well (primecells are gaining popularity at the moment.)  Having it not
> be specific to S3C would be a big advantage, unless of course everyone
> specifically wants to have divergent copies of the same code.

Which is great, until you find out that the S3C PL080 isn't a vanilla
PL080, and has extra registers.

I'm in favour of some form of generic DMA API, but we're going to have
to sort out whether it is dmaengine, dmaengine with some updates or
something entirely new.

The current dmaengine API doesn't have any support for circular buffer
mangement, and from what I remeber of reading stuff last time, adding
to the queue from a buffer done callback is a no-no.

-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.