On Sat, Feb 02, 2013 at 07:06:06PM +0000, Sergei Shtylyov wrote: > Hello. > > On 02-02-2013 22:07, Matt Porter wrote: > > >>>>>>> Move mach-davinci/dma.c to common/edma.c so it can be used > >>>>>>> by OMAP (specifically AM33xx) as well. > > >>>>>> I think this should rather go to drivers/dma/? > > >>>>> No, this is the private EDMA API. It's the analogous thing to > >>>>> the private OMAP dma API that is in plat-omap/dma.c. The actual > >>>>> dmaengine driver is in drivers/dma/edma.c as a wrapper around > >>>>> this...same way OMAP DMA engine conversion is being done. > > >>>> Keeps me wondering why we couldn't have the same with CPPI 4.1 when I proposed > >>>> that, instead of waiting indefinitely for TI to convert it to drivers/dma/ > >>>> directly. We could have working MUSB DMA on OMAP-L1x/Sitara all this time... Sigh. > > >>> That is a shame. Yeah, I've pointed out that I was doing this exactly > >>> the same way as was acceptable for the OMAP DMA conversion since it was > >>> in RFC. The reasons are sound since in both cases, we have many drivers > >>> to convert that need to continue using the private DMA APIs. > > >> In case of CPPI 4.1, we'd only have to convert MUSB DMA driver. Other > >> in-tree CPPI 4.1 having SoCs don't use it for anything but MUSB -- it even is > >> sub-block of their MUSB device, AFAIK (I maybe wrong about Sitaras -- I don't > >> know them well). > > > Well, it's pretty clear to me now that there's good reason for it not > > landing in arch/arm/ so the obvious path is to do the dmaengine > > conversion and put it in drivers/dma/ if it's really a generic dma engine. > > I'm not sure why you express concern over the dma engine api not fitting > > with CPPI 4.1? > > It's not a DMA controller only, it's 3 distinct devices, with the DMA > controller being one among them and using another one, the queue manager, as > some sort of proxy. The third device doesn't exist on OMAP-L1x SoCs -- it's > the buffer manager. Interesting, and you don't see a way to have this split between dmaengine and the musb driver? This all assumes there's even a match as RMK did raise concerns elsewhere in this thread. > > If it doesn't work, work with Vinod to fix the api. It's > > expected, I'm working on dmaengine API changes right now to deal with a > > limitation of EDMA that needs to be abstracted. > > Sorry, now it's TI's task. I no longer have time to work on this (my > internal project to push OMAP-L1x support upstream has expired at Sep 2010) > and my future in MV is very uncertain at this moment. Most probably I'll leave > it (or be forced to leave). Too bad, it's certainly "somebody's task". The people employed by TI have names too. ;) I suspect it falls to Felipe or Kishon these days, but I try to avoid USB as it's generally a source of pain. > > As pointed out, edma.c is already here in arch/arm/, so moving it doesn't > > add something new. It does let us regression test all platforms that use it > > (both Davinci and AM33xx) as I go through the conversion process. > > Could have been the same with CPPI 4.1 in theory if it was added to > mach-davinci/ back in 2009... we'd then only have to move it. EDMA code is > much older of course, so it's probably more justified. Absolutely, timing is everything. I can assure you I've flamed enough people "internally" about leaving this EDMA dmaengine conversion for so long. As you might have guessed, AM33xx is a bit of a driver for it, but all of this would have been quite a bit simpler had somebody taken a little effort and moved edma to dmaengine years ago when slave dma support was added to dmaengine. ;) -Matt -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
