Need Help Enabling HDMI on Debix Model A

[Tarang Raval]

Hi Laurent,

Thanks for the response.

> On Mon, Apr 07, 2025 at 11:10:23AM +0000, Tarang Raval wrote:
> > Hi Laurent,
> >
> > I’m trying to bring up HDMI on the Debix Model A board using the
> > mainline kernel, but I’m currently facing issues.
> >
> > I saw that you tested the patch for HDMI support on this board in
> > mainline, so I am hoping you could help me figure out what might be
> > missing.
> >
> > To clarify — I'm using the prebuilt image provided by Debix, but I replaced
> > the kernel image and the device tree (DTS) file in the /boot directory with
> > ones built from the mainline kernel.
> >
> > I’ve enabled the following configurations in the kernel:
> > CONFIG_DRM_DISPLAY_CONNECTOR=y
> > CONFIG_DRM_IMX8MP_DW_HDMI_BRIDGE=y
> > CONFIG_DRM_IMX8MP_HDMI_PVI=y
> > CONFIG_DRM_IMX_LCDIF=y
> > CONFIG_PHY_FSL_SAMSUNG_HDMI_PHY=y
> >
> > When I boot the board, I see the following HDMI/DRM related logs:
> > debix at imx8mp-debix:~$ dmesg | grep -iE "drm|hdmi"
> > [    0.121979] /soc at 0/bus at 32c00000/display-bridge at 32fc4000: Fixed dependency cycle(s) with /soc at 0/bus at 32c00000/hdmi at 32fd8000
> > [    0.122164] /soc at 0/bus at 32c00000/hdmi at 32fd8000: Fixed dependency cycle(s) with /soc at 0/bus at 32c00000/display-bridge at 32fc4000
> > [    0.127417] /soc at 0/bus at 32c00000/hdmi at 32fd8000: Fixed dependency cycle(s) with /hdmi-connector
> > [    0.127608] /hdmi-connector: Fixed dependency cycle(s) with /soc at 0/bus at 32c00000/hdmi at 32fd8000
> > [    1.947962] imx8mp-dw-hdmi-tx 32fd8000.hdmi: Detected HDMI TX controller v2.13a with HDCP (SAMSUNG HDMI TX PHY)
> > [    1.949220] imx8mp-dw-hdmi-tx 32fd8000.hdmi: registered DesignWare HDMI I2C bus driver
> > [    1.956365] [drm] Initialized imx-lcdif 1.0.0 for 32fc6000.display-controller on minor 0
> > [    2.016601] imx-lcdif 32fc6000.display-controller: [drm] fb0: imx-lcdifdrmfb frame buffer device
> > [    8.380915] systemd[1]: Starting Load Kernel Module drm...
> >
> >
> > I also checked that the display's modeline is recognized under sysfs :
> >
> > root at imx8mp-debix:~# ls /sys/class/drm/card0-HDMI-A-1/
> > connector_id  dpms          modes         subsystem/
> > ddc/          edid          power/        uevent
> > device/       enabled       status
> >
> > However, there is still no HDMI output on the display. Instead,
> > I only see a white blinking cursor on the screen.. I'm not sure
> > what I'm missing.
> 
> The white blinking cursor means the display is working from the kernel
> point of view. What are you expecting, are you running an X server or
> Wayland compositor ?

I'm expecting to see the Ubuntu desktop environment on the HDMI 
display — just like how it appears with the original prebuilt image provided 
by Debix. I'm running the default Ubuntu 22.04 LTS prebuilt image, and I only
replaced the Image and .dtb file

I'm not explicitly launching an X server or Wayland compositor myself

However, based on your response, I now realize that I may also need to 
enable GPU support in the mainline device tree. Specifically, I believe I 
need to enable the gpu2D and gpu3D nodes to allow the graphical 
environment to start properly and render the desktop over HDMI.

Does that sound correct, or is there anything else I should check or 
enable?

Best Regards,
Tarang

> > Could you please help me out or point me in the right direction?
> >
> > Thank you for your time.
> >
> > Best Regards,
> > Tarang
> 
> --
> Regards,
> 
> Laurent Pinchart