On 11/23/2011 05:26 PM, Stephen Warren wrote: > Rob Herring wrote at Wednesday, November 23, 2011 2:55 PM: >> On 11/23/2011 03:25 PM, Stephen Warren wrote: >>> Rob, Grant, >>> >>> Re: http://www.spinics.net/lists/arm-kernel/msg148899.html >>> >>> Background: Tegra's DMA controller needs to be told which DMA "request >>> select" to use for each transfer. The identifies which peripheral to >>> transfer to/from. >>> >>> The Tegra I2S driver needs to know its own "request select" value to >>> pass to the audio driver DMA path. The board files typically provide >>> this to the driver as an IORESOURCE_DMA. I don't think there's any >>> standard binding that creates such a resource when instantiating a >>> platform device from device tree, and the discussions I found when >>> looking for one didn't seem to reach conclusion that there should be >>> one. So, I proposed the following property in the I2S driver's DT >>> binding for this: >> >> I think this is a case of every platform being different and >> IORESOURCE_DMA is not too widely used. Even on PPC, there's not a >> standard way. >> >>> Doc: >>> >>> - dma-channel : The Tegra DMA controller's channel ID for this I2S controller >>> >>> Example: >>> >>> i2s@70002800 { >>> compatible = "nvidia,tegra20-i2s"; >>> reg = <0x70002800 0x200>; >>> interrupts = < 45 >; >>> dma-channel = < 2 >; >>> }; >>> >>> Does that look reasonable? Or, should I pursue some more standardized >>> solution? >> >> I had some discussion with Thomas Abraham about this for the pl330 dma: >> >> http://lists.ozlabs.org/pipermail/devicetree-discuss/2011-September/008269.html >> >> So I would just add a phandle to the dma controller here. > > So you mean just modify the binding as follows: > > apbdma: dma@NNNNN { ... }; > > i2s@70002800 { > dma-channel = < &apbdma, 2 >; > }; > > ... and leave the code I quoted as-is? Right. Although, I think you are possibly missing some other properties for i2s mode like word size and master/slave mode. I think the ideal case is that a single ASoC platform driver for DT could handle multiple SoCs. > > I /think/ the rest of the patch you linked isn't really relevant to Tegra > at present, since it isn't ported to the DMA engine (yet?). > Yes, of course.. Rob -- 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
