HDMi support in u-boot for armStoneA9r2

  • Hello,

    we use armStoneA9r2 boards with a monitor connected via hdmi. The output of the Linux system (our own Yocto based distribution) works fine via hdmi but we want to display messages in U-Boot as well (when running update scripts that take some time).

    We use the F&S version of U-Boot 2020.04 and "U-Boot 2021.04 (Nov 11 2022 - 12:01:25 +0000) for F&S".

    After poking around in the configuration of U-Boot without success i checked the source code and found that "HDMI support is not implemented".


    How can i continue? Any chance that hdmi output in U-Boot gets implemented?

  • HDMI is currently not supported in our U-Boot. The idea in U-Boot is to have a pre-configured display setup with one resolution. However when using HDMI, things get rather complicated, because an HDMI display typically supports many different resolutions and provides information about it in the so-called EDID information. EDID needs an I2C connection to the display to download this info and then the info needs to be interpreted, resulting in a very dynamic setting of the display resolution, which is not what we intended with our simple approach. In addition the HDMI controller in the CPU needs to be configured and also Hot-Plug-Detect needs to be supported. So this part was rather complex and we postponed it when we implemented display support for U-Boot.

    In the meantime, U-Boot has already grown to a size that it merely fits into the 512KB slot that we have reserved for it. Even small additions are typically too much and we actually need to disable some features in newer U-Boot versions to keep its size below 512KB. Which means adding more code for HDMI would also prove difficult because there is simply no room for it.

    Your F&S Support Team

    F&S Elektronik Systeme GmbH
    As this is an international forum, please try to post in English.
    Da dies ein internationales Forum ist, bitten wir darum, Beiträge möglichst in Englisch zu verfassen.