FRDM-IMX93 Display issue

[Jokar4]

Hi,

Im using the FRDM-IMX93 board with yocto linux image ( https://github.com/nxp-imx-support/meta-imx-frdm ). I'm having some issues with a waveshare 4 inch 720x720 resolution display. It simply does not show anything and stays black all the time. It uses HDMI connection and I connect it to the HDMI connector "P5". I'm using imx93-11x11-frdm.dtb and for instance /sys/class/drm/card0-HDMI-A-1/modes is empty when the display is connected (I would expect mode = 720x720). I have also looked into potential missing display-timings and such but with no further success. Got any advice or hints on how to proceed here? I suspect I need to do some DTS modifications or similar but would need some help in pointing out where. For additional information I have used another bigger 15.6 inch HDMI display and it works perfectly fine and it shows 1280x720 under /sys/class/drm/card0-HDMI-A-1/modes.

Regards,
Jonathan

[JorgeCas]

Hello,

In general, LCD panels have a single video mode, and that means it supports a single resolution. In the case of MIPI DSI/LVDS to HDMI bridges, at the end we are using an HDMI monitor which supports different resolutions, and it has a preferred video mode.

You need to change the resolution to 720x720 by edit Weston configuration file:

nano /etc/xdg/weston/weston.ini

Example:

[output]
name=HDMI-A-1
mode=720x720@60
#transform=rotate-90

To enable the new resolution restart Weston service:

systemctl restart weston

In case you are using LVDS to HDMI bridge, you might be seeing only one video mode. This is due to the LDB PLL limitation, as with the current dts PLL setting we are able to generate only 1 clock for the video mode.

You also need to change the PLL settings according to your display resolution in device tree:

LVDS Serializer rate = Pixel Clock x 7 / number of LVDS channels

Example:

&lcdif {
	status = "okay";
	assigned-clock-rates = <4158000000>, <1039500000>;
};

Rebuild the device tree based on the instructions from i.MX Linux User's Guide Chapter 4.5.12 How to build U-Boot and Kernel in stand-alone environment and copy the new dtb on the target board.

Best regards.

[Jokar4]

Thanks for your response. By adding proper clock rates it seems like I got one step further but still a black screen not showing anything. The new clock rate im using is:

assigned-clock-rates = <336000000>, <48000000>;

I also tested the weston config changes with no success. But with "one step further" I mean that for instance now I can see the IT6263 being picked up and used which it was not before. I have attached some logs which might be useful. Any thoughts on next step?

Regards,
Jonathan