Yocto Morty kernel for MIPSfpga

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    Thomas
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    I have some experience with using Yocto and targeting Microblaze and ARM processors so I figured I would try using the meta-img layer to see if I can get something going on the Nexys4 DDR (machine, xilfpga) for a course project. I’ve been at this a few days now and I’m not entirely sure where the disconnect is.

    I began using the SoC project’s 2014.2 Xilinx project and upgraded it to 2016.2. I then upgraded the MIPSfpga core to a more recent version of the HDL. My output bit file can can still boot the original kernel provided in that zip file (MIPSfpga SoC), so that all seems fine as a starting point.

    For the meta-img layer, I paired it up with poky (Morty) as seems to be indicated both by the branch of meta-img and the documentation. I compared the state of the 4.8 kernel (in Morty) with the patches that were required back on the 4.1 kernel used in the MIPSfpga SoC project. At this point it looks like the patches have been pulled in for the xilfpga machine, so I went with it.

    I set the MACHINE for xilfpga and ran bitbake (core-image-minimal). Given the present configuration of this layer, it will produce a separate cpio.gz file system and kernel (vmlinux). Booting the kernel produces panic that a working init was not found (not surprising, since the the defconfig CONFIG_INITRAMFS_SOURCE=”” with this default).

    To setup bundling the kernel with the filesystem as indicated in the SoC Part2 guide for buildroot, I tried modifying the machine definition to bundle the rootfs corresponding to mipsfpga-soc-initramfs:

    INITRAMFS_IMAGE = "mipsfpga-soc-initramfs"
    INITRAMFS_IMAGE_BUNDLE = "1"
    

    The mipsfpga-soc-initramfs image definition points back to core-image-minimal among other things:

    include recipes-core/images/core-image-minimal.bb
    IMAGE_FSTYPES = "${INITRAMFS_FSTYPES}"
    PACKAGE_INSTALL = "${IMAGE_INSTALL}"
    

    The result of building that image (bitbake mipsfpga-soc-initramfs) is a vmlinux-initramfs-xilfpga.bin, which is the kernel and file system combined. When I try to boot that however, I get another kernel panic. This time the error is with /dev/console, stating that I need to make sure my rootfs is okay.

    Kernel panic – not syncing: /dev/console is missing or not a character device!
    Please ensure your rootfs is properly configured
    
    —[ end Kernel panic – not syncing: /dev/console is missing or not a character device!
    

    This is all just a summary of everything I’ve been digging into and comparing over the last few days as I’ve gone deeper into search results on how to debug this.

    Do either of these scenarios sound familiar to anyone? Any debugging steps that I’m leaving out or should look into?

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