DMA device tree configuration

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1. Article purpose[edit source]

This article explains how to configure the DMA internal peripheral when it is assigned to the Linux^® OS. In that case, it is controlled by the Dmaengine overview.

The configuration is performed using the Device tree mechanism that provides a hardware description of the DMA internal peripheral, used by the STM32 DMA Linux driver and by the DMA framework.

The hardware description is a combination of:

STM32 DMA peripheral
and STM32 DMA client

If the peripheral is assigned to another execution context, refer to How to assign an internal peripheral to a runtime context article for guidelines on peripheral assignment and configuration.

2. DT bindings documentation[edit source]

Complete device tree bindings can be found at this location: ^[1].

3. DT configuration[edit source]

This hardware description is a combination of the STM32 microprocessor device tree files (.dtsi extension) and board device tree files (.dts extension). See the Device tree for an explanation of the device tree file split.

STM32CubeMX can be used to generate the board device tree. Refer to How to configure the DT using STM32CubeMX for more details.

3.1. DT configuration (STM32 level)[edit source]

At device level, the DMA is declared as follows:

dma2: dma@48001000 {
    compatible = "st,stm32-dma";
    reg = <0x48001000 0x400>;
    interrupts = <GIC_SPI 56 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 57 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 58 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 59 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 60 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 68 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 69 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 70 IRQ_TYPE_LEVEL_HIGH>;
    clocks = <&rcc DMA2>;
    resets = <&rcc DMA2_R>;
    #dma-cells = <4>;
    st,mem2mem;
    dma-requests = <8>;
    dmas = <&mdma1 8 0x11 0x1200000a 0x48001008 0x00000020 1>,
           <&mdma1 9 0x11 0x1200000a 0x48001008 0x00000800 1>,
           <&mdma1 10 0x11 0x1200000a 0x48001008 0x00200000 1>,
           <&mdma1 11 0x11 0x1200000a 0x48001008 0x08000000 1>,
           <&mdma1 12 0x11 0x1200000a 0x4800100C 0x00000020 1>,
           <&mdma1 13 0x11 0x1200000a 0x4800100C 0x00000800 1>,
           <&mdma1 14 0x11 0x1200000a 0x4800100C 0x00200000 1>,
           <&mdma1 15 0x11 0x1200000a 0x4800100C 0x08000000 1>;
    dma-names = "ch0", "ch1", "ch2", "ch3", "ch4", "ch5", "ch6", "ch7";
};

The DTS file is located under arch/arm/boot/dts/stm32mp151.dtsi

Warning

This device tree part is related to STM32 microprocessors. It must be kept as is, without being modified by the end-user.

3.2. DT configuration (board level)[edit source]

Do not change the DMA device tree at board level.

4. How to configure the DT using STM32CubeMX[edit source]

The STM32CubeMX tool can be used to configure the STM32MPU device and get the corresponding platform configuration device tree files.
The STM32CubeMX may not support all the properties described in the above DT bindings documentation paragraph. If so, the tool inserts user sections in the generated device tree. These sections can then be edited to add some properties and they are preserved from one generation to another. Refer to STM32CubeMX user manual for further information.

5. References[edit source]

Please refer to the following links for additional information:

↑ Documentation/devicetree/bindings/dma/st,stm32-dma.yaml

[1] Documentation/devicetree/bindings/dma/st,stm32-dma.yaml

[1]