[U-Boot-Users] CFG_NO_FLASH configuration parameter

[U-Boot-Users] CFG_NO_FLASH configuration parameter

[Mustafa Çayır]

Hi,

Could you point out  CFG_NO_FLASH configuration parameter? If CFG_NO_FLASH is defined, do it means that there is really no flash in system? if so, how is system able to boot from flash?

Thanks.

[U-Boot-Users] CFG_NO_FLASH configuration parameter

[Wolfgang Denk]

In message <002201c63848$88dbba20$9e01120a@bilisim.local> you wrote:
> 
> Could you point out  CFG_NO_FLASH configuration parameter? If
> CFG_NO_FLASH is defined, do it means that there is really no flash in

Yes, CFG_NO_FLASH means that there is no flash on the board.

> system? if so, how is system able to boot from flash?

Simple: it does not boot from flash.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"Don't worry about people stealing your ideas. If your ideas are  any
good, you'll have to ram them down people's throats."  - Howard Aiken

[U-Boot-Users] CFG_NO_FLASH configuration parameter

[Mustafa Çayir]

hi Denk,

Thanks for your reply. 

> Yes, CFG_NO_FLASH means that there is no flash on the board.
> 
>> system? if so, how is system able to boot from flash?
> 
> Simple: it does not boot from flash.

if CFG_NO_FLASH is defined, as you said, means there are no flash memories, where do initial boot instructions located? 

Regards.

 .globl _start
_start:
 li r21, BOOTFLAG_COLD /* Normal Power-On: Boot from FLASH */
 b boot_cold
 sync

[U-Boot-Users] CFG_NO_FLASH configuration parameter

[Wolfgang Denk]

In message <006d01c63871$b26c26d0$9e01120a@bilisim.local> you wrote:
> 
> if CFG_NO_FLASH is defined, as you said, means there are no flash
> memories, where do initial boot instructions located? 

For example in RAM. Think of a PCI card which is plugged  in  a  host
system,  where  the  host runs some software to upload some code into
the PCI card's memory which then gets executed. See  the  PN62  board
for such a configuration.

There are several other methods to load U-Boot into RAM - for example
by using an initial bootstrap loader as used on some system  to  boot
from NAND flash or dataflash.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"One planet is all you get."

[U-Boot-Users] CFG_NO_FLASH configuration parameter

[Jerry Van Baren]

Wolfgang Denk wrote:
> In message <006d01c63871$b26c26d0$9e01120a@bilisim.local> you wrote:
>> if CFG_NO_FLASH is defined, as you said, means there are no flash
>> memories, where do initial boot instructions located? 
> 
> For example in RAM. Think of a PCI card which is plugged  in  a  host
> system,  where  the  host runs some software to upload some code into
> the PCI card's memory which then gets executed. See  the  PN62  board
> for such a configuration.
> 
> There are several other methods to load U-Boot into RAM - for example
> by using an initial bootstrap loader as used on some system  to  boot
> from NAND flash or dataflash.
> 
> Best regards,
> 
> Wolfgang Denk

...and that RAM has to be connected to CS0 (typ) if it is truly "no ROM" 
(no flash).

* If it is SDRAM, someone other than u-boot must initialize it so that 
it is functional when reset is released.

* Someone other than u-boot must load u-boot (or other program) into the 
RAM while the processor is held in reset, and then release reset.

* The processor doesn't care if it is booting out of RAM or ROM or core 
memory.  It fetches instructions and executes them.  It always does the 
same thing on release of reset - you cannot change it other than what 
the chip manufacturer provided for.  It is your responsibility to have 
instructions in the right place and available when you release reset 
(e.g. for the 603e core lowboot: 0x00000100, highboot: 0xFFFFF100).

Disclaimer: I believe there are systems out there that use CFG_NO_FLASH 
but actually have a minimal boot memory (ROM/flash/eeprom) that 
initialize SDRAM and then spin until the host downloads the program 
(e.g. u-boot) and says "go".  The above discussion doesn't apply to them.

gvb