Re: [ECOS] Redboot ROM image using RAM?

[Mark Salter <msalter at redhat dot com>]

On Mon, 2005-07-25 at 11:04 -0500, Don Osburn wrote:
> Greetings, and I hope this is the correct group this time...
> 
> We have a new custom board we are attempting to bring up and are having some
> difficulty with Redboot.  Our design is intel IXP425 reference with the
> following exceptions.  We are using an IXP420 with an LXT971A PHY attached
> to ethernet 0 only.  (The ref design has LXT972A attached to ethernet 0 and
> ethernet1 on an IXP425.)
> 
> We have successfully burned redboot into flash and can boot.  The problem is
> we can not understand where / how to load the snapgear images into flash to
> boot linux.
> 
> I am using the NPE-enabled binaries for Redboot v2.01.  I use the
> redboot_ROM.bin file from the ixdp425 directory and burn it into Intel
> strata_flash.  It boots with a warning about NPE A.  Not sure about that
> warning, but I can do an fconfig and fis init and everything looks fine.
> (The warning may be do to the PHY difference.)
> 
> At this point I do a
> RedBoot> load -r -v -b 0x01600000 zImage
> and it works.  However, when I attempt a
> RedBoot> load -r -v -b 0x00800000 ramdisk.gz
> 
> The processor hangs.  After poking around in memory for a while, we are
> pretty confident that what is happening is redboot is using memory around
> 0x00800000 to run itself.  So, when we attempt to write to that area in RAM,
> we are stomping on the bootloader. (?)  Why is that?  Our understanding was
> if you loaded the ROM image, it should not use RAM?

RedBoot is mostly C code, so of course it uses RAM. The startup banner
which RedBoot prints will tell you what RAM area is available for the
user. For IXDP425, I see:

RAM: 0x00000000-0x10000000, [0x00029888-0x0ffd1000] available

This tells me that 0x00029888-0x0ffd1000 is not being used by RedBoot.
If RedBoot is indeed using RAM in this area, then it is a bug. I would
make sure that the zImage and ramdisk.gz files actually fit into the
available RAM area without overrunning into RAM used by RedBoot.

> 
> We are having great difficulty understanding the documentation on this.
> What is the difference between the ROM and the RAM images?  Also, when we
> attempted to burn / load the RAM image, it doesn't work at all.

ROM RedBoot is located in and runs from ROM (although it also uses RAM
for .data, .bss, etc).

RAM RedBoot is meant to be loaded into and run from RAM.

ROMRAM RedBoot is located in ROM, but copies itself into RAM and
thereafter executes from RAM exclusively.

--Mark


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