[U-Boot] Linux booting speed up.

Wolfgang Denk wd at denx.de
Thu Nov 20 16:57:06 CET 2008

Dear Michele Venturi,

please keep the mailing list on Cc:

In message <908E0D8EBCBE4AAE9A5EFDCD66CE45A6 at ebneuro.intranet> you wrote:
> Many thanks for your prompt support and suggestions !
> I add comments I hope will be useful.
> 1)
> > But of course U-Boot can load and uncompress the  ramdisk  image  and
> > pass  the  address  of  the uncompressed image to the kernel. See the
> > FAQ.
> I found that this feature works, but the had to be enabled (on my old 1.1.2 
> sources) for the
> CONFIG_AT91RM9200DK board
> target, or the Flash EEPROM to SDRAM.trasfer of uncompressed ramdisk image
> would be simply skipped...

This is intentional. It makes no sense to copy the image to RAM. The
uncompressor can read the compressed data from flash as well.

> This is true even for the recent u-boot-2008-tar.bz2 release:

As mentioned, this is intentional.

> Of course it should be changed in :
> #if defined(CONFIG_B2) || defined(CONFIG_EVB4510) || 
> defined(CONFIG_ARMADILLO) || defined(CONFIG_AT91RM9200DK)

No, it should not be changed. Instead, the Linux kernel should be
fixed to allow to take a compressed ramdisk from a flash address.

Again, as mentioned before: patches have been posted here several
times before.

> 2)
> > Also keep in mind that turning of the checksums (verify=no) helps a
> > bit.
> This feature works, but it seems to me that the usage of the environment 
> variable
> "verify" is not documented in the DULG manual.

It seems to me that you did not search carefully. See at
http://www.denx.de/wiki/view/DULG/UBootEnvVariables :

	verify: If set to n or no disables the checksum calculation
	over the complete image in the bootm command to trade speed
	for safety in the boot process. Note that the header checksum
	is still verified.

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Always leave room to add an explanation if it doesn't work out.

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