[U-Boot-Users] MPC83xx - previous patch to set MBAR

Kim Phillips
2007-08-02T00:20:09Z

On Wed, 1 Aug 2007 15:20:22 -0500
"Keith Mund" <keith.mund@clearcube.com> wrote:

> There was a u-boot 1.1.3 patch for start.S posted on the Freescale LTIB

posts concerning u-boot should go to the u-boot-users list (cc'd).

> site:
> http://www.bitshrine.org/gpp/u-boot-1.1.3-mpc83xx-cpu-4.patch
>
> The end result simply adds a line to set MBAR to match IMMRBAR.
>
> lis r3, CFG_IMMRBAR at h
> ori r3, r3, CFG_IMMRBAR at l
> stw r3, IMMRBAR(r4)
> + mtspr MBAR, r3
>
> Are these patches routinely added to the mainstream u-boot code?
>
> Is there any reason why this fix is not a good idea?
>
does setting MBAR really fix anything?

MBAR doesn't live up to its name. It's a general-purpose scratch
register - the hardware doesn't do anything with it. So, wrt integrity
within u-boot itself, I see no point/value in setting it. If some
piece of software needs temporary storage, it can set it and use it as
it wishes, independent of u-boot.

Kim