On Tuesday 18 March 2014, Santosh Shilimkar wrote: > > On Tuesday 18 March 2014 11:38 AM, Arnd Bergmann wrote: > > On Tuesday 18 March 2014 20:54:44 Vinod Koul wrote: > >> On Mon, Mar 17, 2014 at 03:37:47PM -0400, Santosh Shilimkar wrote: > >>>>> To simplify this bit more, you can think of this as DMA channels, flows > >>>>> are allocated and DMA channels are enabled by DMA engine and they remains > >>>>> enabled always as long as the channel in use. Enablling dma channel > >>>>> actually don't start the DMA transfer but just sets up the connection/pipe > >>>>> with peripheral and memory and vice a versa. > >>>>> > >>>>> All the descriptor management, triggering, sending completion interrupt or > >>>>> hardware signal to DMAEngine all managed by centralised QMSS. > >>>>> > >>>>> Actual copy of data is still done by DMA hardware but its completely > >>>>> transparent to software. DMAEngine hardware takes care of that in the > >>>>> backyard. > >>>> So you will use the dmaengine just for setting up the controller. Not for actual > >>>> transfers. Those would be governed by the QMSS, right? > >>>> > >>> Correct. > >>> > >>>> This means that someone expecting to use dmaengine API will get confused about > >>>> this and doing part (alloc) thru dmaengine and rest (transfers) using some other > >>>> API. This brings to me the design approach, does it really make sense creating > >>>> dmaengine driver for this when we are not fully complying to the API > >>>> > >>> Thats fair. The rationale behind usage of DMEngine was that its the closest > >>> available subsystem which can be leveraged for this hardware. We can > >>> pretty much use all the standard DMAEngine device tree parsing as well as > >>> the config API to setup DMAs. > >>> > >>> I think you made your stand clear, just to confirm, you don't prefer this > >>> driver to be a DMAEngine driver considering it doesn't fully complying to > >>> the APIs. We could document the deviation of 'transfer' handling to avoid > >>> any confusion. > >> Yup, a user will just get confused as the driver doenst conform the dmaengine > >> API. Unless someone comes up witha strong argument on why it should be > >> dmaengine driver and what befits we see form such a model, i would like a > >> damengine driver to comply to standard API and usage. > > > > I think it would be possible to turn the QMSS driver into a library and have > > the packet DMA code use the proper dmaengine API by calling into that code. > > > > The main user of packet DMA (the ethernet driver) would however still have > > to call into QMSS directly, so I'm not sure if it's worth the effort. > > > Its not. Am going to move this driver along with QMSS which is one > of the options we discussed. Ok, fair enough. Looking forward to the patches. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
