Re: Understanding MLO and X-loader

[Jason Kridner]

On Dec 13, 9:25 am, "favor tang" <tang...@gmail.com> wrote:
> I also want to know this! every time I need copy MLO at first, and the
> second coping file is u-boot.bin ,and the uImage at last,
> why I should copy these files in that sequence?  and what is the MLO used
> for? as far as i know, the u-boot can boot the board enough.

MLO fits entirely on on-chip memory and configures the external memory
for use. u-boot requires more memory than what is on-chip. If you
are using the on-flash u-boot, then all you really need on the SD card
is a kernel and a root file system.

>
> thanks
> /favor
>
> On Sat, Dec 13, 2008 at 5:52 PM, Søren Steen Christensen <
>
> sorenschristen...@stofanet.dk> wrote:
>
> > Hi,
>
> > You can find documentation for ROM code initialization/booting in the TRM
> > (spruf98b.pdf) chapter 25.4...
>
> > The MMC/SD card booting in particular is described in chapter 25.4.7.6...
>
> > Best Regards
> >  Søren
>
> > -----Oprindelig meddelelse-----
> > Fra: beagl...@googlegroups.com [mailto:beagl...@googlegroups.com] På
> > vegne af John (USP)
> > Sendt: 13. december 2008 09:24
> > Til: beagl...@googlegroups.com
> > Emne: [beagleboard] Re: Understanding MLO and X-loader
>
> > MLO is just a signed version of x-loader using omap3430gp-signer.pl
>
> > Regards,
>
> > > -----Original Message-----
> > > From: beagl...@googlegroups.com
> > > [mailto:beagl...@googlegroups.com] On Behalf Of GimpMaster
> > > Sent: Friday, December 12, 2008 10:22 AM
> > > To: Beagle Board
> > > Subject: [beagleboard] Understanding MLO and X-loader
>
> > > Hello,
>
> > > I'm trying to understand exactly what is MLO. From the documentation I
> > > have found all I really know is that it has to be on the first sector
> > > of the SD card and that it is used in the boot process. From other
> > > people I've heard that it is just x-load.bin.ift renamed.
>
> > > However when I go to the
> >http://www.angstrom-distribution.org/demo/beagleboard/
> > > the file sizes are different (meaning either different versions or
> > > they are not the same).
>
> > > So does the OMAP boot ROM when booting from an SD card look for a file
> > > named MLO? If somebody could point me to a good document or site that
> > > might clear things up.
>
> > > Thanks in advance.
>
> > No virus found in this incoming message.
> > Checked by AVG -http://www.avg.com
> > Version: 8.0.176 / Virus Database: 270.9.17/1846 - Release Date: 12-12-2008
> > 18:59
>
>

[favor tang]

hi. do you means that either MLO or u-boot.bin can boot up the board?

/thanks

[Søren Steen Christensen]

To be 100% clear: ROM code loads MLO from MMC card in case of MMC booting.

The MLO binary then loads u-boot.bin, which then again loads the kernel image.

 

As such, it should be possible to combine the MLO and u-boot.bin binaries into one binary called MLO in case you can make it fit in the OMAP35xx internal memory. The image needs to fit into internal memory only, since the ROM code doesn’t assume anything about external memory, and thereby can’t use it…

 

I hope this answered your question?

 

But again, as Jason wrote: If you are using the on-flash u-boot you really only need to copy the kernel image and rootfs to the SD card…

 

Best regards

  Søren

Checked by AVG - http://www.avg.com

[John Beetem]

Here is a generic tutorial on the Linux boot process. While not
specific to BeagleBoard, it does cover the conceptual layers nicely.

http://www.ibm.com/developerworks/linux/library/l-linuxboot/index.html?S_TACT=105AGX03&S_CMP=ART

The "Stage 1 Boot Loader" for BeagleBoard is MLO. Its purpose is load
the Stage 2 Boot Loader.

The "Stage 2 Boot Loader" for BeagleBoard is u-boot. Its purpose is
to load the Linux kernel.

Hope this helps.
John