Re: [MiNT] 040/060 MMU tree builder

[Michael Schwingen <rincewind@discworld.dascon.de>]

On Wed, May 19, 1999 at 11:18:21PM +0000, Odd Skancke wrote:
> 
>  Ok, but if the boot is a warm boot, it should not do anything with the
> current mmu settings I think. Cause with a warm boot, all memory and
> memory related things have already been set up. Anyway, since the mmu
> setup runs after the warm boot needed to reset phystop etc., it is not set
> up until then anyway.. hmm.. trying to set the mmu up before a warm boot
> is another thing I haven't tested....

TOS *does* re-initialize all hardware (including the memory controller) on a
warm boot, so I don't see why it should not re-initialize the PMMU, too.

The original TOS 3.06 *does* turn off and re-initialize the PMMU on every
reset, although I am not sure now how that was modified on the hades.

> Memory Protection unless the MMU is already enabled. Then, in MiNT reset
> handler it should set the mmu registers to the original tranlation tree,
> as found when it started. This would make it possible to use one "layout"

No. It is the ROMs task to get the system up to a stable state, no matter if
it is a warm or a cold boot, and this includes setting up a good PMMU
mapping if necessary on the machine.

This may be bad for you if you want to patch it, but IMHO this is
preferrable if the TOS *does* init the PMMU the right way.

> until the next cold-boot. I mean, during a cold boot, everything hardware
> related is set up, and the memory map is created. Then on sucessive
> warm-boots, the current "hardware" configuration should be preserved. Does
> this sound reasonable?

No. The only diffeence between cold and warm start is that the memory test
and size detection is skipped on warm starts. I want the system to come up
clean after a reset, and a reset is not meant as a way to half-restart the
OS after patching around.

cu
Michael
-- 
Michael Schwingen, Ahornstrasse 36, 52074 Aachen