Re: Is there a binding for IORESOURCE_DMA population?

[Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>]

On Fri, Jul 15, 2011 at 08:11:41PM +0200, Arnd Bergmann wrote:
> On Friday 15 July 2011 18:45:38 Tabi Timur-B04825 wrote:
> > 
> > On Fri, Jul 15, 2011 at 11:32 AM, Shawn Guo <shawn.guo-KZfg59tc24xl57MIdRCFDg@public.gmane.org> wrote:
> > 
> > > First of all, using powerpc dma-channel binding on such dma event
> > > seems not reflecting the hardware facts.  Secondly, the binding in
> > > this case (below) looks silly.  Thirdly, device driver need to make
> > > code change for simply getting a dma event number.
> > 
> > Take a look at p1022ds.dts or mpc8610hpcd.dts.  We create separate DMA
> > channel nodes on Freescale PowerPC parts because the channels really
> > are independent.  On these two boards, some of the DMA channels are
> > used by the async DMA driver, and two of the channels are used by the
> > audio driver.
> 
> I think this is much better than using IORESOURCE_DMA fields, which
> basically are only well-defined for PC-style i8237 DMA controllers
> used in stuff like floppy drives and ISA sound cards.
> 
> However, we should find a way to standardize finding the dma_chan
> for an platform_device based on a phandle. Maybe a little helper
> that will scan a well-known property (dma-channels?) for phandles
> to a device_node that is backing a struct dma_chan.

That sounds appropriate.

g.