On Sun, Apr 14, 2013 at 08:37:21AM -0500, Timur Tabi wrote:
Markus Pargmann wrote:
I do not think it is possible. For example imx27 ssi does support DMA but for specific boards we have to use fiq instead (phycore-ac97). So I would prefer to define the DMA in the chip dtsi file and choose fiq, if necessary, in the board dts.
I'm not completely familiar with the way i.MX SSI bindings work, but isn't there some property that says, "this SSI needs to use this DMA channel"? So if that property is missing, then it means that there's no link between the SSI and a DMA channel, and so you need to use FIQ.
For example, for PowerPC bindings, we have this:
ssi@16000 { compatible = "fsl,mpc8610-ssi"; cell-index = <0>; reg = <0x16000 0x100>; interrupt-parent = <&mpic>; interrupts = <62 2>; fsl,mode = "i2s-slave"; codec-handle = <&cs4270>;--> fsl,playback-dma = <&dma00>; --> fsl,capture-dma = <&dma01>;
So on PowerPC, if these two properties are missing, then we would use interrupt mode.
In general, imx27 does support SSI with DMA, for example MACH_IMX27_VISSTRIM_M10 does use SSI with DMA. But there are special boards like Eukrea TLV320 and phycore-ac97 that have to use FIQ instead. All of them have a imx27 chip. The imx27 SSI node (not posted yet) using the generic DMA bindings:
ssi1: ssi@10010000 { compatible = "fsl,imx21-ssi"; reg = <0x10010000 0x1000>; interrupts = <14>; dmas = <&dma 13 &dma 12 &dma 15 &dma 14>; dma-names = "tx", "rx", "tx1", "rx1"; clocks = <&clks 26>; clock-names = "ipg"; fsl,mode = "i2s-slave"; status = "disabled"; };
So instead of defining the dma channels in imx27.dtsi, we could define them only in board dts files. But that would duplicate the DMA property for every board using DMA. The alternative is the "fsl,imx-fiq" property as introduced in this patch.
Regards,
Markus
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