Subject: Re: MMU problems (Was: JavaStation w/ OBP3 - some progress)
To: None <uwe@ptc.spbu.ru>
From: Pete Zaitcev <zaitcev@redhat.com>
List: port-sparc
Date: 04/17/2001 02:06:22
Yeah, I forgot that OBP uses 0xf0nnnnnn area. It conflicts with
Linux too and was one of the reasons to use PROLL. The worst
part was that Linux kernel uses a zillion of small fixed location
segments for DVMA, SBus mappings, and ta-da-da-da - vaunted
Linux phis-to-virt 1:1 mapping that gives Linux VM such an
edge over BSD VM (yeah, right!). I looked at all that crap and
decided not to move kernel base.

PK thinks that ``JS1 seems to be a "transient" machine'',
so I am sure he'll be happy to learn that all IIep based
JavaStations are the same.

When I worked at Sun I wrote to firmworkers alias (got no
reply), and bugged Dave Paktor with little success,
trying to understand whose idea it was to step over
the custom UNIX base. IIRC, Dave said that he was indeed
the author, and he was willing to build a new ROM for
me *if he had time*, and JavaOS worked just fine, and it
was a Linux bug anyways. At that point I gave up on it.

Uwe, like I said, use PROLL and be happy. It's not that
bad a kludge. Well, it's GPLed. Big deal! You complile
with GPLed compiler too :)

-- Pete

P.S. Actually, OBP in JS is a piece of cake. Years ago
Sun contracted me to port Linux on set-top-box that they built
for AOL (roughly a JavaStation too). That thing had NO OBP and
a Diba made ROM instead, and its memory map was optimized
for Chorus. To that end, Diba ROM used 256MB 2nd level page
mappings. PROLL was a life saver there!