[U-Boot] IXP425 TEXT_BASE

From: Teh Kok How <khteh@smartbridges.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] IXP425 TEXT_BASE
Date: Wed, 5 Aug 2009 11:22:00 +0800	[thread overview]
Message-ID: <006c01ca157b$e574acb0$1933000a@smartbridges.com> (raw)
In-Reply-To: <20090804155700.BA3948340728@gemini.denx.de>

Hi;
	I understand Wolfgang's argument but setting the TEXT_BASE to this
arbitrary high address (DRAM_end - U-boot_size(_end - _start)) does not make
sense. I am new to ARM arch but in PowerPC and MIPS, the TEXT_BASE is always
set to the reset vector and in ARM, the reset vector is at 0 or 0xFFFF0000.
I have tried both values but still failed to boot u-boot on the board....:-(

Regards,
Teh

-----Original Message-----
From: u-boot-bounces@lists.denx.de [mailto:u-boot-bounces at lists.denx.de] On
Behalf Of Wolfgang Denk
Sent: Tuesday, August 04, 2009 11:57 PM
To: Darius Augulis
Cc: u-boot at lists.denx.de
Subject: Re: [U-Boot] IXP425 TEXT_BASE

Dear Darius Augulis,

In message <4A784702.40806@gmail.com> you wrote:
>
> > No. TEXT_BASE is an absolute address.
> 
> yes, but depends on the physical RAM base and size.

Only on ARM (and other architectures that copied it's broken
implementation). TEXT_BASE is an absolute address (in the boot flash)
on PowerPC.

> could you please explain more? why to the end of RAM?

YOu want to have a maximum of contiguous RAM available to load Linux
kernel, ramdisk images etc.

> for example I have 16MB RAM, base is 0x10000000. TEXT_BASE = 0x10400000.
> Why is better to set this to 0x10F00000 ? To have more stack and malloc 
> memory? But U-boot will never exceed such limit? Please explain where I 
> am wrong. Thanks!

With RAM from 0x10000000...0x10ffffff you should probably put
TEXT_BASE at 0x10f80000 which then would leave you some 15 MB of
contiguous RAM for your use.

With your setup you jusy have some 3+ MB below U-Boot and some 11+ MB
above it. It makes not much sense to have U-Boot sitting right in the
middle of precious RAM like this.

Best regards,

Wolfgang Denk

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DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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