Re: Relocating bootwrapper causes kernel panic

[Scott Wood <scottwood@freescale.com>]

On Thu, 5 Aug 2010 11:33:44 -0700
Shawn Jin <shawnxjin@gmail.com> wrote:

> >> > Before the flat tree was accessed, I checked the DTLB and didn't find
> >> > any entry related to 0xc0be4300. After the exception, I found the
> >> > following DTLBs.
> >> >
> >> > 30 : 02 =A0c0be4000 =A0 4KB ------ -> 00000000
> >> > 31 : 00 =A0fa000000 =A0 8MB VI-S-M -> fa000000
> >> >
> >> > The DTLB#30 doesn't seem right. Why would it map to 0x0? I think this
> >> > should be something like 00be4000?
> >
> > Note that the valid bit is clear -- it's not mapping to anything.
>=20
> Did the exception handler try to set a TLB here but the setting was
> not completed?

Probably.  You won't have any page tables yet, much less an entry for
the device tree.

> >> I think the cause is clear now. But how to fix it? Two questions:
> >> 2. If the DTLB miss exception handler is not the right guy to load a
> >> proper TLB entry, how can I set one entry based on the link_address
> >> and the address of the flat dt blob?
> >
> > Given how early in the boot process it is, it's probably going to need
> > to be handled specially.
>=20
> What APIs can I use to set up DTLBs?

I don't think there is one that works on 8xx.  You'll could hack up
initial_mmu, or else write some C code to insert an 8xx TLB entry.

-Scott