[ECOS] Booting rootfs over TFTP with RedBoot
Gary Thomas
gary@mlbassoc.com
Fri May 14 13:40:00 GMT 2010
On 05/14/2010 05:37 AM, Stephen Crocker wrote:
> I am currently attempting to test a system using OpenWRT on a Gateworks
> Cambria board with an XScale CPU. I have produced a new rootfs for
> experimentation purposes but I do not want to overwrite the rootfs that
> is currently in the flash.
>
> I have successfully used the following commands in the past to load
> kernels remotely with an existing rootfs:
> load -r -b 0x00800000 -h 192.168.1.241 -m tftp zImage
> exec
>
> However, I am unable to see how I can do the same for a rootfs loaded
> over TFTP. The flash has the following layout:
> RedBoot> fis list
> Name FLASH addr Mem addr Length Entry point
> RedBoot 0x50000000 0x50000000 0x00080000 0x00000000
> linux 0x50080000 0x00800000 0x00100000 0x00800000
> rootfs 0x50180000 0x00800000 0x01E60000 0x00800000
> FIS directory 0x51FE0000 0x51FE0000 0x0001F000 0x00000000
> RedBoot config 0x51FFF000 0x51FFF000 0x00001000 0x00000000
> RedBoot>
>
> Clearly the kernel and rootfs are intended to be loaded into RAM at the
> same location, but this is not possible if the rootfs is to be loaded
> over TFTP. Is there any way to specify a different rootfs offset to the
> kernel?
>
> The rootfs currently in flash is very important for testing something
> else, so I do not want to risk losing it.
>
The file system (rootfs) used by Linux is *not* loaded into RAM,
rather used directly from the FLASH.
Given the size of the file system, it would seem that your only
choice would be to overwrite the FLASH with your test image.
Do you have any way of copying/preserving the FLASH before trying
such an operation?
Another possibility would be to run your test file system via NFS.
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Gary Thomas | Consulting for the
MLB Associates | Embedded world
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