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From: Andre Renaud <andre@bluewatersys.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] cpu/arm926ejs/start.S question
Date: Fri, 08 Jul 2011 09:38:52 +1200	[thread overview]
Message-ID: <4E16276C.3080303@bluewatersys.com> (raw)

Hello,
I am working on an i.MX25 board, and would like to know the recommended
mechanism for putting code in before the first instruction in the
executable, but outside the *_spl system.

Basically, the i.MX25 has a smart boot rom in the CPU, which will
extract the first block, and interpret it (as data, rather than
instructions). However, if I just use the linker script to put this
block before start.S, then U-Boot relocation gets messed up, as _start
is now not the beginning of the image, and a lot of the calculated
offsets are wrong.

At the moment I have this working with the following change in start.S:
--- cpu/arm926ejs/start.S       (revision 36)
+++ cpu/arm926ejs/start.S       (working copy)
@@ -53,6 +53,9 @@

 .globl _start
 _start:
+#ifdef CONFIG_PRE_START_INCLUDE
+#include CONFIG_PRE_START_INCLUDE
+#endif
        b       reset
 #ifdef CONFIG_PRELOADER
 /* No exception handlers in preloader */

and I then #define CONFIG_PRE_START_INCLUDE to be the assembler for the
i.MX25 specific boot code.

Is there a nicer way to go about this?

Regards,
Andre

             reply	other threads:[~2011-07-07 21:38 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-07-07 21:38 Andre Renaud [this message]
2011-07-07 22:34 ` [U-Boot] cpu/arm926ejs/start.S question Simon Glass
2011-07-07 22:40   ` Andre Renaud
2011-07-08  0:54 ` Fabio Estevam
2011-07-08  1:20   ` Andre Renaud
2011-07-08  1:38     ` Fabio Estevam
2011-07-08  1:42       ` Andre Renaud
2011-07-08  6:13     ` Stefano Babic
2011-07-11  4:59   ` Andre Renaud
2011-07-11 15:00     ` Fabio Estevam

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