[U-Boot-Users] CFG_NO_FLASH configuration parameter
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.
In message 002201c63848$88dbba20$9e01120a@bilisim.local you wrote:
Could you point out CFG_NO_FLASH configuration parameter? If CFG_NO_FLASH is defined, do it means that there is really no flash in
Yes, CFG_NO_FLASH means that there is no flash on the board.
system? if so, how is system able to boot from flash?
Simple: it does not boot from flash.
Best regards,
Wolfgang Denk
hi Denk,
Thanks for your reply.
Yes, CFG_NO_FLASH means that there is no flash on the board.
system? if so, how is system able to boot from flash?
Simple: it does not boot from flash.
if CFG_NO_FLASH is defined, as you said, means there are no flash memories, where do initial boot instructions located?
Regards.
.globl _start _start: li r21, BOOTFLAG_COLD /* Normal Power-On: Boot from FLASH */ b boot_cold sync
In message 006d01c63871$b26c26d0$9e01120a@bilisim.local you wrote:
if CFG_NO_FLASH is defined, as you said, means there are no flash memories, where do initial boot instructions located?
For example in RAM. Think of a PCI card which is plugged in a host system, where the host runs some software to upload some code into the PCI card's memory which then gets executed. See the PN62 board for such a configuration.
There are several other methods to load U-Boot into RAM - for example by using an initial bootstrap loader as used on some system to boot from NAND flash or dataflash.
Best regards,
Wolfgang Denk
Wolfgang Denk wrote:
In message 006d01c63871$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
participants (4)
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Jerry Van Baren -
Mustafa Çayir -
Mustafa Çayır
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Wolfgang Denk