[U-Boot-Users] arm920t RAM relocation broken?

[Cory T. Tusar]

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Ulf Samuelsson wrote:
> ----- Original Message -----
> From: "Cory T. Tusar" <ctusar at videon-central.com>
> To: <u-boot-users at lists.sourceforge.net>
> Cc: <peter.pearse at arm.com>
> Sent: Thursday, March 06, 2008 10:05 PM
> Subject: [U-Boot-Users] arm920t RAM relocation broken?
> 
> 
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>> Commit d4fc6012 added an #ifdef CONFIG_AT91RM9200 construct around the
>> RAM relocation bits in cpu/arm920t/start.S.  More directly, it added an
>> entire secondary relocation snippet surrounded by an
>> #ifdef CONFIG_BOOTBINFUNC construct.
>>
>> It appears that this second implementation was later removed in commit
>> 80767a6c, but the #ifdef CONFIG_AT91RM9200 logic was not removed also.
>>
>> Is RAM relocation only intended to function on at91rm9200 boards, or
>> shall I submit a patch fixing the above?
>>
>> - -Cory
> 
> Does this mean that the AT91RM9200 always relocates?
> Then the code is simply wrong.

No, there's an additional #ifndef CONFIG_SKIP_RELOCATE_UBOOT construct
around the relocation code.  The issue is that nothing /but/ AT91RM9200
/ever/ relocates the way it's currently coded.

The relevant chunk (lines 181-201) from cpu/arm920t/start.S:

#ifdef	CONFIG_AT91RM9200

#ifndef CONFIG_SKIP_RELOCATE_UBOOT
relocate:				/* relocate U-Boot to RAM	    */
	adr	r0, _start		/* r0 <- current position of code   */
	ldr	r1, _TEXT_BASE		/* test if we run from flash or RAM */
	cmp     r0, r1                  /* don't reloc during debug         */
	beq     stack_setup

	ldr	r2, _armboot_start
	ldr	r3, _bss_start
	sub	r2, r3, r2		/* r2 <- size of armboot            */
	add	r2, r0, r2		/* r2 <- source end address         */

copy_loop:
	ldmia	r0!, {r3-r10}		/* copy from source address [r0]    */
	stmia	r1!, {r3-r10}		/* copy to   target address [r1]    */
	cmp	r0, r2			/* until source end addreee [r2]    */
	ble	copy_loop
#endif	/* CONFIG_SKIP_RELOCATE_UBOOT */
#endif


> If you run from a serial flash, then the code is already relocated
> and is executing from SDRAM at this point, so the code will crash.

Yes.  This should be handled by CONFIG_SKIP_RELOCATE_UBOOT in the
board's configuration, shouldn't it?

- -Cory


- -- 
Cory T. Tusar
Embedded Systems Engineer
Videon Central, Inc.
2171 Sandy Drive
State College, PA 16803
(814) 235-1111 x316
(814) 235-1118 fax


"There are two ways of constructing a software design.  One way is to
 make it so simple that there are obviously no deficiencies, and the
 other way is to make it so complicated that there are no obvious
 deficiencies."  --Sir Charles Anthony Richard Hoare


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