On Wed, Dec 21, 2011 at 09:37:04AM +0530, Vinod Koul wrote: > On Tue, 2011-12-20 at 20:54 +0800, Shawn Guo wrote: > > On Tue, Dec 20, 2011 at 02:54:04PM +0530, Vinod Koul wrote: > > > On Tue, 2011-12-13 at 23:48 +0800, Shawn Guo wrote: > > > > I have been working on -rc recently, and have not noticed the failure > > > > until I ran next tree today. The mxs-mmc driver is broken on next > > > > tree because the DMA_NONE was left over from the dma_transfer_direction > > > > migration for mxs-dma and its client drivers. > > > > > > > For DMA transfer, the NONE direction makes no sense? > > > > > > In your conetext, what are you trying to achieve? > > > > > The mxs-dma controller has a feature to program peripheral registers > > with given values (mxs-dma PIO mode). This is designed to pipeline > > the operations. For example, we can put mxs-mmc controller register > > values into scatter list as one element together with actual data. > > Triggering the mxs-dma, the dma will program the values into mxs-mmc > > controller register to set up and enable mxs-mmc, and then dma > > continue transfer data from/to mxs-mmc. All these get done in one > > dmaengine_submit(). > > > > And DMA_NONE was used to let mxs-dma know this is a PIO operation. > Sorry am little lost here. Why would DMA driver bother with a PIO mode, > that is something only peripheral driver would know about, mmc in your > case. > The term PIO here may not the one on your mind. I call it 'mxs-dma pio'. In this mode, mxs-dma hardware can write values into mmc controller register without cpu involved. > So what you are saying is the your dma has the capability to program the > peripheral registers in case of PIO mode, but why wouldn't the > peripheral driver do that instead? > Yes, I'm saying mxs-dma has the capability to program the peripheral registers, and that's called 'mxs-dma pio' mode. -- Regards, Shawn -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
