On Fri, Feb 14, 2025 at 12:35:41PM +0000, J. Neuschäfer wrote:

On Mon, Feb 10, 2025 at 02:39:13PM -0500, Frank Li wrote:

quoted

On Fri, Feb 07, 2025 at 10:30:22PM +0100, J. Neuschäfer via B4 Relay wrote:

quoted

From: "J. Neuschäfer" <redacted>

The devicetree bindings for Freescale DMA engines have so far existed as
a text file. This patch converts them to YAML, and specifies all the
compatible strings currently in use in arch/powerpc/boot/dts.

Signed-off-by: J. Neuschäfer <redacted>
---

[...]

quoted

Need ref to dma-common.yaml?

Sounds good, but I'm not sure what to do about the #dma-cells property,
which is required by dma-common.yaml.

There aren't many examples of DMA channels being explicitly declared in
device trees. One example that I could find is the the xilinx_dma.txt
binding:


	axi_vdma_0: axivdma@40030000 {
		compatible = "xlnx,axi-vdma-1.00.a";
		#dma_cells = <1>;
		reg = < 0x40030000 0x10000 >;
		dma-ranges = <0x00000000 0x00000000 0x40000000>;
		xlnx,num-fstores = <0x8>;
		xlnx,flush-fsync = <0x1>;
		xlnx,addrwidth = <0x20>;
		clocks = <&clk 0>, <&clk 1>, <&clk 2>, <&clk 3>, <&clk 4>;
		clock-names = "s_axi_lite_aclk", "m_axi_mm2s_aclk", "m_axi_s2mm_aclk",
			      "m_axis_mm2s_aclk", "s_axis_s2mm_aclk";
		dma-channel@40030000 {
			compatible = "xlnx,axi-vdma-mm2s-channel";
			interrupts = < 0 54 4 >;
			xlnx,datawidth = <0x40>;
		};
		dma-channel@40030030 {
			compatible = "xlnx,axi-vdma-s2mm-channel";
			interrupts = < 0 53 4 >;
			xlnx,datawidth = <0x40>;
		};
	};

	...

	vdmatest_0: vdmatest@0 {
		compatible ="xlnx,axi-vdma-test-1.00.a";
		dmas = <&axi_vdma_0 0
			&axi_vdma_0 1>;
		dma-names = "vdma0", "vdma1";
	};

It has #dma_cells (I'm sure #dma-cells was intended) on the controller.


Another example is in arch/powerpc/boot/dts/fsl/p1022si-post.dtsi:

	dma@c300 {
		dma00: dma-channel@0 {
			compatible = "fsl,ssi-dma-channel";
		};
		dma01: dma-channel@80 {
			compatible = "fsl,ssi-dma-channel";
		};
	};

	...

	ssi@15000 {
		compatible = "fsl,mpc8610-ssi";
		cell-index = <0>;
		reg = <0x15000 0x100>;
		interrupts = <75 2 0 0>;
		fsl,playback-dma = <&dma00>;
		fsl,capture-dma = <&dma01>;
		fsl,fifo-depth = <15>;
	};


There, the DMA channels are used directly and without additional
information (i.e. #dma-cells = <0>, althought it isn't specified).

I had another look at dma-common.yaml and it explicitly requires
#dma-cells to have a value of at least 1, so this second idea won't
work.


Best regards,
J. Neuschäfer