[U-Boot] Linux booting speed up.

[Wolfgang Denk]

Dear Michele,

In message <BA4D40DBFB024E51BCB0052BCFB5199E at ebneuro.intranet> you wrote:
> I am using UBoot on a AT91RM9200 target supporting Linux 2.4.27.
> I would like to accelerate the boot process, while keeping Kernel and 
> RamDisk compressed on Flash EPROM.
...
> Instead of copying the compressed RamDisk Flash code to SDRAM, and then 

Rather than doing this, I would teach  the  kernel  to  deal  with  a
ramdisk  image  in  flash.  This  has  been done before. Patches (and
references to the patches) have been postewd on  this  list  multiple
times.

> to decompress the RamDisk, can U Boot uncompress the RamDisk on behalf of 
> the Kernel, then presenting

U-Boot can do nothing "on behalf of  the Kernel", because U-Boot
doesn't exist any more once the kernel booted.

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.

> The idea is to skip the step of simply copying a compressed image from Flash 
> to SDRAM,
> but directly uncompressing the Flash image to SDRAM.

This is easier to solve by teaching your Linux kernel to be a bit more
clever.

> Sure this can be accomplished patching U Boot ad hoc, but can it be done 
> through standard commands and variables ?

Yes, see above.

Also keep in mind that turning of the checksums (verify=no) helps a
bit.

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
Nothing ever becomes real until it is experienced.       - John Keats