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Last Post 13 Nov 2014 07:55 AM by  Adam Ford
Linux kernel on OMAP-L138 (experimenter kit)
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Henk Hakkesteegt
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13 Nov 2014 05:12 AM

    We would like to run our software under a Linux kernel on the OMAP-L138 (not on the external SD-card). We have an OMAP-L138 eXperimenter Kit with C674x DSP and started trying out some manuals for loading kernels (and later software) on the device, but ran into some trouble. Herewith some observations:

     

    -          In manual 1021604B_AM1808_OMAP-L138_Linux_User_Guide we used the provided Virtual Machine SDK. In paragraph 6.2 we flash the UBL and application u-boot.bin, but when powering on the development kit the device finishes its initialization info with the error

     

    “Wrong image format for bootm command

    ERROR: can’t get image kernel”

     

    No changes have been made to any sources so this should be expected to work.

     

    -          Executing a similar procedure but then just from Windows 7, following manual 1015906C_OMAP-L138_AM1808_U-Boot_Labs we end up with the same error.

     

    -          We tried to recover the Flash memory according to manual 1023340B_AN556_SOM-M1_SPI_Flash_Recovery, hence without loading a u-boot.bin file. This worked fine.

     

    -          Now when trying to create an Ethernet-connection, following 1015906C_OMAP-L138_AM1808_U-Boot_Labs,  we fail again. The IP-properties are set properly on both the OMAP as well as the host PC (see attachments), according to manual. The MAC-address of the board has been set as provided on the label on the OMAP. This was attempted to be done according to manual 1023340B_AN556_SOM-M1_SPI_Flash_Recovery, Chapter 6. However, the variable ethaddr remains unlisted as an environment variable after this operation, so it is additionally set using “setenv ethaddr 00:08:EE:06:6C:3B”. However, pinging the host PC always results in “Host 192.168.120.76 is not alive”. Firewall on host PC is disabled; tried with cross-over and normal UTP cable.

     

    -          Finally, for this current kernel we still require the SD-card. Due to the sea of manuals floating everywhere it is unclear how to be able to have our kernel and software running without the SD-card.

     

    All in all nothing really goes well, though all manuals have been followed exactly. Research on the internet has not leaded to any solutions yet. We hope you can give us some assistance on this.
    Adam Ford
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    --
    13 Nov 2014 07:55 AM
    Sorry if the documentation comes across confusing.

    The L-138 uses a series of files to boot linux, and u-boot is only one part of that. In addition to the u-boot files, a usable kernel is required and a root file system (rootfs).
    Section 6.2 of 1021604B_AM1808_OMAP-L138_Linux_User_Guide is limited to only u-boot and it does not contain a bootable kernel. Section 6.3 goes on to describe how to work with u-boot and to set it up to load the kernel from various locations, but it assumes you have the kernel and rootfs already compiled and ready to go from sections 4 and 5.

    When restoring per the instructions in 1023340B_AN556_SOM-M1_SPI_Flash_Recovery, there are some images that have factory u-Boot, uImage (kernel) as well as the rootfs and when you restore to one of those files, it fully boots.

    The instructions to get the mac address restored in 1023340B_AN556_SOM-M1_SPI_Flash_Recovery, Chapter 6 work, but you must reboot after step 1 as stated at the beginning of step 2. If you don't reboot after step 1, the ethaddr won't show up and everything after that falls down.

    If you are still having trouble, copy the contents of your terminal screen from the beginning of the original boot, the stuff you did on section 6, the reboot and the environmental variables after reboot, and post them back here, so I can see what might be going wrong.

    As far as instructions to boot without an SD card, I first need to know which option you would prefer.
    - Over the network, but this requires a a host computer to be running on the same network
    - From flash using Ramdisk
    - From Flash using JFFS

    The advantage of RAMdisks is that the entire filesystem operates from RAM which is faster than flash when executing, and each time the system reboots, it goes back to how the rootfs was originally compiled. This is nice where you want the same environment each time, but it takes RAM to make this work and it takes a little longer on bootup to copy the rootfs to RAM.

    The advantage of JFFS is that any changes are persistent over power-cycles, but should someone or something alter critical files, it is permanent.

    If you tell me which method you prefer, I can try to help walk you through the steps.

    adam
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