[U-Boot-Users] How big should U-Boot be for a 405EP based board?

[U-Boot-Users] How big should U-Boot be for a 405EP based board?

[Conn Clark]

Hello,

	I have finsihed with the preliminary port of U-Boot for our latest 
product(at least enough to test ram, flash, serial, and maybe ethernet). 
We have a single flash chip on our board that will be either 4MB or 8MB. 
Due to the way that the 405EP boots up I thought that the smallest I 
could ever get U-Boot's binary image was two megs. However, when I 
compile and link it it turns out to be 256K. Is this correct or am I 
mistaken on the minimal size of U-Boot for a 405EP based board?


Thanks in advance,

Conn
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Conn Clark
Engineering Stooge				clark at esteem.com
Electronic Systems Technology Inc.		www.esteem.com

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  This email address may be used to communicate to Conn Clark
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[U-Boot-Users] How big should U-Boot be for a 405EP based board?

[Wolfgang Denk]

In message <3FFDFC1D.200@esteem.com> you wrote:
> 
> We have a single flash chip on our board that will be either 4MB or 8MB. 
> Due to the way that the 405EP boots up I thought that the smallest I 
> could ever get U-Boot's binary image was two megs. However, when I 

You maust be doing something very strange. 

> compile and link it it turns out to be 256K. Is this correct or am I 
> mistaken on the minimal size of U-Boot for a 405EP based board?

U-Boot easily fits in 170...240 kB.

You did not ptovide any details, so I can only speculate that you put
the U-Boot start address somewhere in lower  flash  memory.  Remember
that  the  405 uses 0xFFFFFFFC as reset address, so if you put U-Boot
at 0xFF000000 the binary image will have to cover all the range  from
0xFF000000  to  0xFFFFFFFF (= 16 MB) even if only 200 kB are actually
used. Just put U-Boot to a high  address  in  flash,  something  like
0xFFFC0000

Best regards,

Wolfgang Denk

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[U-Boot-Users] How big should U-Boot be for a 405EP based board?

[Conn Clark]

Wolfgang Denk wrote:
> In message <3FFDFC1D.200@esteem.com> you wrote:
> 
>>We have a single flash chip on our board that will be either 4MB or 8MB. 
>>Due to the way that the 405EP boots up I thought that the smallest I 
>>could ever get U-Boot's binary image was two megs. However, when I 
> 
> 
> You maust be doing something very strange. 
> 
> 
>>compile and link it it turns out to be 256K. Is this correct or am I 
>>mistaken on the minimal size of U-Boot for a 405EP based board?
> 
> 
> U-Boot easily fits in 170...240 kB.
> 
> You did not ptovide any details,

I apologise.

> so I can only speculate that you put
> the U-Boot start address somewhere in lower  flash  memory.  Remember
> that  the  405 uses 0xFFFFFFFC as reset address, so if you put U-Boot
> at 0xFF000000 the binary image will have to cover all the range  from
> 0xFF000000  to  0xFFFFFFFF (= 16 MB) even if only 200 kB are actually
> used. Just put U-Boot to a high  address  in  flash,  something  like
> 0xFFFC0000
> 
> Best regards,
> 
> Wolfgang Denk
> 

	As you stated, the reset vector is at 0xFFFFFFFC . Unfortunatly uppon 
reset the EBC0_B0CR address is set to 0xFFE00000 and the size is set to 
2MB . This puts our reset vector right in the middle of our 4MB flash 
chip. We are using a bottom boot block flash part and I was hoping to 
use the smaller sectors for the environment. Our main goal right now  is 
the verification of the hardware so efficiency of flash usage is not a 
priority ( Fortunatly our kernel and ram disk will fit in the remaining 
  2MB though this will probably change in the future). I placed U-boot 
at the beginning of the flash address space just to get things done.

	Although I am certain that U-boot actual code consumes only about 200K 
to 256K, with how I defined it my binary image should be 2MB. My problem 
is my binary image is only 256K in size and not the 2MB I was expecting.

Sorry for not being more specific.

More misc. details from board specific header file.

#define FLASH_BASE0_PRELIM	0xFF800000  /* FLASH bank #0	*/

/*-----------------------------------------------------------------------
  * Start addresses for the final memory configuration
  * (Set up by the startup code)
  * Please note that CFG_SDRAM_BASE _must_ start at 0
  */
#define CFG_SDRAM_BASE		0x00000000
#define CFG_MAX_SDRAM_SIZE	0x04000000
#define CFG_FLASH_BASE		0xFF800000
#define CFG_MONITOR_BASE	CFG_FLASH_BASE
#define CFG_MONITOR_LEN		(256 * 1024)    /* Reserve 256 kB for Monitor	*/
#define CFG_MALLOC_LEN		(256 * 1024)	/* Reserve 256 kB for malloc()	*/



PS.
I remember a few years ago someone in the PPC-Boot mailing list said 
something about a split PPC-Boot image. Would this be possible in 
U-Boot? Seeing that no matter what we do U-Boot is going to occupy a 
sector in the middle of our flash memory map it would allow us to use 
some of the space wasted.

Thanks in advance

	Conn Clark

-- 

*****************************************************************
   If you live at home long enough, your parents will move out.
  (Warning they may try to sell their house out from under you.)
*****************************************************************

Conn Clark
Engineering Stooge				clark at esteem.com
Electronic Systems Technology Inc.		www.esteem.com

Stock Ticker Symbol				ELST

"clark at esteem.com" Copyright 2000 By Electronic Systems Technology
  This email address may be used to communicate to Conn Clark
  provided it is not being used for advertisement purposes, unless
  prior written consent is given. This email address may not be
  sold under any circumstances. All other rights reserved.