Why doesn't uart2 node include dmas in imx8mm.dtsi?

[takeshi100]

Hi.

In imx8mm.dtsi, uart2 node don't include the dmas.

But other uart node (1. 2 and 4) include the dmas.

Why? and What is the impact of not including the dmas?

■ imx8mm.dtsi

https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/freescale/imx8mm.dtsi

uart1: serial@30860000 {

compatible = "fsl,imx8mm-uart", "fsl,imx6q-uart";

reg = <0x30860000 0x10000>;

interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>;

clocks = <&clk IMX8MM_CLK_UART1_ROOT>,

<&clk IMX8MM_CLK_UART1_ROOT>;

clock-names = "ipg", "per";

dmas = <&sdma1 22 4 0>, <&sdma1 23 4 0>;

dma-names = "rx", "tx";

status = "disabled";

};

uart3: serial@30880000 {

compatible = "fsl,imx8mm-uart", "fsl,imx6q-uart";

reg = <0x30880000 0x10000>;

interrupts = <GIC_SPI 28 IRQ_TYPE_LEVEL_HIGH>;

clocks = <&clk IMX8MM_CLK_UART3_ROOT>,

<&clk IMX8MM_CLK_UART3_ROOT>;

clock-names = "ipg", "per";

dmas = <&sdma1 26 4 0>, <&sdma1 27 4 0>;

dma-names = "rx", "tx";

status = "disabled";

};

uart2: serial@30890000 {

compatible = "fsl,imx8mm-uart", "fsl,imx6q-uart";

reg = <0x30890000 0x10000>;

interrupts = <GIC_SPI 27 IRQ_TYPE_LEVEL_HIGH>;

clocks = <&clk IMX8MM_CLK_UART2_ROOT>,

<&clk IMX8MM_CLK_UART2_ROOT>;

clock-names = "ipg", "per";

status = "disabled";

};

Best Regards.

[JorgeCas · Accepted solution]

Hello,

This is because UART2 is used for debug purposes. If you check the device tree, the debug UART port doesn't use DMA.

Best regards.