Enable SPI driver in apalis IMX8QM

Technical Support
1

Hello team,

We are doing yocto project, for that we have to interface DAC with SPI, buit we are not seeing any spi driver under /dev tree, could please provide me steps to add nodes in dtsi and configure the spi driver in SBC.

2

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To enable the SPI driver on an Apalis iMX8QM module and ensure that the SPI device appears under the /dev tree, you need to follow these steps:

1. Modify the Device Tree

You need to add the SPI node in the device tree source (DTS) file. Here is an example of how you can modify the device tree to enable SPI and bind it to the spidev driver.

Example Device Tree Overlay

Create a device tree overlay file, for example, apalis-imx8qm-spi-overlay.dts:

/dts-v1/;
/plugin/;

/ {
    compatible = "toradex,apalis-imx8qm";

    fragment@0 {
        target = <&ecspi1>;
        __overlay__ {
            status = "okay";
            spidev@0 {
                compatible = "spidev";
                reg = <0>;
                spi-max-frequency = <10000000>;
                status = "okay";
            };
        };
    };
};

In this example:

  • &ecspi1 refers to the SPI1 controller. You may need to adjust this based on the specific SPI controller you are using.
  • spidev@0 is the SPI device node with a chip select of 0.
  • spi-max-frequency sets the maximum SPI clock frequency.

2. Build the Device Tree Overlay

Compile the device tree overlay to generate the .dtbo file:

dtc -I dts -O dtb -o apalis-imx8qm-spi-overlay.dtbo apalis-imx8qm-spi-overlay.dts

3. Deploy the Device Tree Overlay

Copy the compiled .dtbo file to the boot partition of your Apalis iMX8QM module. You can use scp or any other method to transfer the file.

scp apalis-imx8qm-spi-overlay.dtbo root@<your_board_ip>:/boot/overlays/

4. Enable the Device Tree Overlay

Edit the overlays.txt file located in the /boot directory on your Apalis iMX8QM module to include your new overlay:

vi /boot/overlays.txt

Add the following line to the fdt_overlays variable:

fdt_overlays=apalis-imx8qm-spi-overlay.dtbo

Please, also check if these links can help you solve your problem:

Maximum transfer size 4096 bytes with spidev driver for SPI on Colibri imx6.

3

How to add device tree overlay

4

Hi, @karthikgowda6!

I’ve tried to find a driver for this IC, but, apparently, there is no driver for this specific model. So, it won’t be possible to add an SPI node or driver to our device tree.

I saw that you asked another question, so I’ll keep the answers here since the topic is related.

Another option in your case is using SPIDEV to communicate with the DAC from user space. Please, refer to this article to find out how it is done, and feel free to ask if you have any doubts.

Best regards.
Lucas Azeituno

5

Hi @lucas_az.tx
Tried this method, we are able see the spi under /dev but the problem is once we reboot it will disappear from that, can you give a solution to reflect it at /dev automatically once we update the dtsi.

6

Hi, @karthikgowda6!

As you are using Apalis iMX8QM, you can enable the SPIDEV overlay (if it isn’t already enabled) and it should be enough to automatically start SPIDEV.

Here you can find out how to enable a device tree overlay, and here you can find the name of the pre-built SPIDEV overlay to enable it.

As you can see in this article, you may have to use an external code (like the sample code used) to do some tests with SPIDEV.

Please, let me know if you face any doubts.

Best regards.
Lucas Azeituno