Hi,
I have a problem booting the current u-boot-imx version on a MX28EVK via USB. The i.MX28 CPU supports a special boot mode where the image (sb boot stream) is downloaded via USB device (all DIP switches in position 'off' on the EVK). The CPU's internal bootrom implements a HID device in this mode. Freescale provides a download tool "sb_loader" for this purpose. There is also a GPL'd implementation based on libusb.
So back to my problem:
I build u-boot from the u-boot-imx repository. This runs fine when booting from SD/MMC or SPI-flash. But the console stays dark when using the USB download mode. USB download works fine with the Freescale provided U-Boot sources together with the imx-bootlets SPL code.
Now I digged a little bit deeper to find out the cause:
When downloading via USB I saw the SPL running correctly. board_init_ll() (arch/arm/cpu/arm926ejs/mx28/start.S) runs through correctly. Then control is passed back to the bootrom. That's where things end as far as I can see.
The 2nd stage of u-boot is not started.
The USB boot mechanism is not documented that detailed. Is it possible that the SPL code overwrites the bootroms ivt and in consequence crashes the bootrom's USB code? Any further ideas?
Matthias