On Wed, Apr 25, 2012 at 02:31:27PM +0530, Laxman Dewangan wrote: > Hi Vinod, > > On Monday 23 April 2012 06:47 PM, Laxman Dewangan wrote: >> On Monday 23 April 2012 06:36 PM, Russell King - ARM Linux wrote: >>> On Mon, Apr 23, 2012 at 05:47:03PM +0530, Laxman Dewangan wrote: >>>> Hi Russell, >>>> On Monday 23 April 2012 02:11 PM, Vinod Koul wrote: >>>>> On Fri, 2012-04-20 at 17:46 +0530, Laxman Dewangan wrote: >>>>>> Thanks Vinod for quick review. >>>>> Since I was on vacation, I hadn't noticed Russell has already sent the >>>>> patches for omap dma support. >>>>> http://permalink.gmane.org/gmane.linux.ports.arm.omap/75034 >>>>> >>>>> It would be nice if both the efforts are coordinated. >>>>> >>>>> Btw I like the virtual channel support introduced by Russell >>>>> >>>> Can you please point me the virtual channel related change? I am not >>>> able to locate this like search for function vchan_* (). >>>> My driver is also on same line but not used vchan_* and also having >>>> support for cyclic transfer. >>> It's only been posted in RFC form on linux-arm-kernel and linux-omap >>> lists. The specific patch is: >>> >>> http://lists.arm.linux.org.uk/lurker/message/20120418.101116.082b350f.en.html >>> >>> I wouldn't call it perfected yet, but usable. It doesn't have any >>> knowledge about cyclic transfers either. >> For simple dma, it is straight to use the virt_chan and it reduce lots >> of code from tegra_dma as most of it moved to the virt_dma. >> >> Some points which I am looking are: >> 1. Extending this for cyclic support: >> In cyclic mode, we need to call callback after period_len but do not >> want to free descriptors. So either I need to add flag on the desctiptor >> to no delet and so when vc->desc_free(vd); is called from callback, it >> will not delete the descriptor. >> >> 2. With very prep call, we are allocating descriptor. Is it is possible >> to allocate some desc in advance and then keep using them. The >> complexity is that if we allocate the desc in advance, we need to >> allocate the desc and sq_req list and maintain the two different lists >> as we dont know the sg_len in advance. >> >> 3. vchan_cookie_complete() is not possible in the cyclic mode as we >> dont want to call dma_cookie_complete() but just want to do following >> two thing: >> >> list_add_tail(&vd->node,&vc->desc_completed); >> tasklet_schedule(&vc->task); >> >> if we extend this function to bypass dma_cookie_complete(&vd->tx); or >> rather than calling this api, directly call the above apis. >> > > > I had a communication with Russell on another change thread and > understand that some more work need to be done in virt_chan to support > cyclic one. Yes, and I said I would get to it in due course - I need to add support so that the OMAP ASoC support can be moved over to DMA engine, and that's one of the next few drivers I will be looking at. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
