LinuxBIOS in 512KB flash

[Hieu T. Tran]

Ron and Eric,

Thank you for the response.

The problem that we're having is that the generated romimage
positions reset_vector / ROMTOP at 0xFFFF0, resulting in an
image size of ~ 1MB.  Put another way, reset_vector is at offset
1MB on the flash device.  At boot, the system fetches the 
address at 0xFFFF0, and executes the code there.  As this 
address is truncated to 0x7FFF0 on our platform, or offset 512KB 
of flash, which is more or less random junk rather than the 
intended reset_vector.

To work around this problem, we're trying various methods to 
force reset_vector / ROMTOP to 0x7FFF0.  It appears that there
are several ways to do this, ranging from adorning the build
config file with various ROMTOP, ROMSIZE, and PAYLOAD_SIZE settings,
to providing a customized ldscript.ld file for the mainboard.  

What I'd like to know is if there is a simple way to accomplish this.
Also, I would be much oblidged for pointer to any document, if 
exists, that prescribes how to construct Config file for a given 
platform.  I suspect other developers would enjoy this as well.

-- HT


-----Original Message-----
From: linuxbios-admin at clustermatic.org
[mailto:linuxbios-admin at clustermatic.org]On Behalf Of Eric W Biederman
Sent: Tuesday, October 08, 2002 5:41 PM
To: Hieu T. Tran
Cc: linuxbios at clustermatic.org
Subject: Re: LinuxBIOS in 512KB flash


"Hieu T. Tran" <htran at viosoft.com> writes:

> We're working to port LinuxBIOS to a via 133 platform
> with a 512KB boot flash.  We believe that the flash is
> wired such that on reset, 0xFFFF0 is mapped to 0x7FFF0
> on the flash, which is slightly below 512KB on the flash.

That sounds correct.
Though I would normally use the mapping at: 0xFFFFFFF0 
and not even mess with the legacy stuff.

> We have been trying various config file settings
> (ROMTOP, ROMSIZE, PAYLOAD_SIZE) to position ROMTOP and 
> reset_vector accordingly without much success.  Simply
> getting a larger flash wont help since the board will
> only recognize the first 512KB.  Has anyone solved this
> problem?  

What exact problem are you having?  When you build romimage
it always places the entry point at the end of the rom.

Eric
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