Verdin AM62 - Sitronix ST7701 based 480*480 MIPI DSI Display

Hi,

I’m trying to get a display to work on a Verdin AM62 Dual on our custom board. We use a 4" TFT with ST7701s controller and MIPI DSI interface for control. So far, I can’t see anything on the screen.

The driver panel-sitronik-st7701 has been modified. Changes include the init sequence and the value of some registers, as indicated by the manufacturer.
I added the driver as a module in the kernel config. lsmod shows the driver in the DRM section.
But the dmesg file does not contain a message debugging the driver, and neither does the console when I remove and then probe the driver.

I created a device-tree overlay file. I am not sure if this is correct. My main device tree file is based on k3-am62-verdin.dtsi and k3-am62-verdin-dev.dtsi.

My custom board has the hardware option of running the Riverdi MIPI DSI LCD and it works fine with it and your overlay. My image is based on the tdx-reference-minimal-image (Kirkstone branch in Yocto).

If anyone could let me know how to check the installation of the driver and if the device tree part is okay, it would be nice.

TDX-INFO :
Software summary
Bootloader: U-Boot
Kernel version: 6.1.83-6.9.0-devel+git.dd30c7ec04b8 #1 SMP PREEMPT Wed Oct 2 13:07:10 UTC 2024
Kernel command line: root=PARTUUID=54285ef8-02 ro rootwait console=tty1 console=ttyS2,115200 consoleblank=0 earlycon=ns16550a,mmio32,0x02800000
Distro name: NAME=“TDX Wayland with XWayland”
Distro version: VERSION_ID=6.9.0-devel-20241115074444-build.0
Distro variant: -
Hostname: verdin-am62-15478858

Hardware info
HW model: Toradex Verdin AM62 WB on Verdin Development Board
Toradex version: 0075 V1.2A
Serial number: 15478858
Processor arch: aarch64

dmesg.txt (29.8 KB)


rfa6400e-awh-mnn.dtsi (797 Bytes)

Regards,

Megane

Hi, I’m the Toradex AI Assistant. The Toradex Support team will follow up with you shortly!

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Hello Megane,

Thank you for reaching out with your display setup issue on the Verdin AM62. Let’s go through some steps to help you verify your driver installation and device tree configuration:

  1. Driver Verification:

    • Since lsmod shows the driver, it indicates that the module is loaded. However, the absence of messages in dmesg suggests that the driver might not be initializing correctly. Consider enabling debug messages in the driver code to increase verbosity and gain more insights.
    • Check if the driver is correctly bound to the display device by examining /sys/class/drm/ to see if the display is listed.
  2. Device Tree Overlay:

    • Ensure your device tree overlay is correctly applied by checking the boot logs for messages indicating successful application.
    • Verify that the compatibility strings in your overlay match the driver and hardware specifications.
    • Review the initialization sequence and register settings in your overlay to ensure they align with the manufacturer’s specifications for the display.
  3. Comparison with Reference Designs:

    • Since your custom board works with the Riverdi MIPI DSI LCD, compare the configurations and settings used for that display with your current setup. This might help identify any discrepancies.

By following these steps, you should be able to identify any issues with the driver or device tree configuration. If you have further questions or need additional clarification, feel free to ask.

Best regards,
Toradex AI Assistant

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

TI AM62 Computer on Module - Verdin AM62.

Hello @mthevenot,

In your .dtsi file, you are not enabling the dss node, which is needed to get the video output that is transmitted via MIPI-DSI.
Adding the following to your .dtsi file should suffice to address this:

&dss {
	status = "okay";
};

Otherwise, the software configuration seems correct.
The only thing that seems incorrect is the pinout of the connector.
As it is a custom pinout, I cannot know which is correct, but on the image you sent, the table and the schematics snippet do not coincide.
It looks like the connector is inverted, so please double check if this is correctly connected.

Best Regards,
Bruno

Hello @bruno.tx,

Thanks for your reply. I have added the correction to the overlay.

I have checked my hardware signals and everything is fine. I can see the backlight on (as the software does not drive it). I know it seems inverted when you look at the schematics. It is the inverted pinning of the connector on the custom board that gives this impression.

The screen still won’t start. I have added dev_err() debug lines to each function but I don’t get any more messages from the driver. I don’t know if I need to enable an option for this to work.

Regards,
Megane

Hello @mthevenot,

Thanks for the update.
What I think may be the issue then is that the device tree with the customizations is not being applied.
How are you configuring your image to use your custom device tree and device tree overlays?

Best Regards,
Bruno

For now, I configure my image using patches.
I started from the k3-am62-main.dtsi file which I modified according to the hardware and requirements of my custom board. This is the 0001-Modifications-pour-la-carte-porteuse-HT.patch file.
This patch validated the hardware on the custom board. I have even been able to apply your overlay via /boot/overlays.txt and get the Riverdi screen working.
Then, I created a second patch (0001-Ajout-dts-cran.patch) which adds the rfa6400e-awh-mnn.dtsi file to the compilation source of the device tree.

What I can say is that when I added the dss section, I was able to see booting logs about that part. But I don’t know if that’s enough to say this method is working.

Regards,
Megane

0001-Ajout-dts-cran.patch (913 Bytes)
0001-Modifications-pour-la-carte-porteuse-HT.patch (29.0 KB)
rfa6400e-awh-mnn.dtsi (804 Bytes)

Hello @mthevenot,

It is unclear what is wrong with the current configuration.

The following points may be related to your current issue:

  • Double-check that there are no display overlays enabled in /boot/overlays.txt . By default the MIPI-DSI to HDMI adapter overlay is enabled, it must not be enabled.
  • Add debug prints to the display driver, to see which functions are being called. This way you can understand if the driver is being loaded and which steps of the initialization are actually taking place. Maybe some part of the initialization code needs to be in a different function on the driver.

Best Regards,
Bruno