[U-Boot-Users] RTC for MPC5200

Wolfgang Denk wd at denx.de
Thu Jan 8 23:56:52 CET 2004

In message <20040108210501.GA4693 at timension.com> you wrote:
> Good morning.  I have a couple of questions.  After struggling with an initrd

What exactly is the problem? The procedure is fairly well  documented
in the DULG, and a ready-to-run image is supplied with the ELDK. Just
boot it...

> boot for a few days, I said "heck with it" and just made /dev/hda2 my root
> device.  Given that the kernel is in flash, and the devices I need are
> compiled in (and I don't have module support), is there any reason to
> mess around with an initrd-style boot, given that we absolutely know 
> what the hardware config is going to be?  It works like a charm with the 

A ramdisk image (loaded from flash) is one way to provide an embedded
system  that  is  100%  bullet-proof  agains  unexpected  reboots  or

> default DENX Sys-V init, from the ppc-82xx tree, by the way, though I will
> have to prune some services.

Also, a more leaner setup like the busybox-based SELF  used  for  our
defualt  ramdisk  images  boots much, much faster than the full-blown
SysV init stuff.

> The other question regards the real time clock on the MPC5200.  Unless I am
> seriously overlooking something, this does not appear to be implemented, yet,
> yes?  The register structure doesn't look too arcane.  Is anybody working on
> this?  I am tempted, but nobody wants to roll in code from a rank novice.  The

You  will  not  be  judged  by  years  of  experience,  or   by   any
certificates. It's just the quality of the code that matters :-)

Seriously: don't worry, just go on, do it, and submit a patch. If  it
needs improvements somebody else will help.

> project we're working on needs a self-contained clock.  I notice that u-boot
> provides rtc services, but isn't that more properly a kernel function?  I'm
> a little fuzzy on the dividing line.

Support for the RTC is not exactly needed in U-Boot. But it  is  very
convenient.  It  is  much easier to debug in U-Boot, and you can just
test in the firmware  if  the  RTC  is  really  running  iunstead  of
debugging  a  Linux device driver. Also, the clock on some RTCs needs
to get started before you can use them.  Not  all  Linux  drivers  do

Best regards,

Wolfgang Denk

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