Re: loongson2f: evbmips or new port ?

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Aug 11, 2011 at 09:55:10AM -0500, David Young wrote:
> On Wed, Aug 10, 2011 at 11:55:25PM +0200, Manuel Bouyer wrote:
> > Hi,
> > I have a loongson2f-based system (lemote fuulong) booting into sysinst;
> > ethernet, serial, USB are working, IDE is almost there (I've an
> > interupt issue that I've worked around with a hugly hack, but I still
> > hope to have it working properly :)
> > For now the code is in arch/loongson, based on a few bits from 
> > evbmips/gdium,
> > and from OpenBSD code (OpenBSD supports gdiun, fuulong and others).
> > 
> > The code can easily be turned into evbmips/loongson, but there's
> > a few things to consider before going one way or another.
> > 
> > First, loongson2 kernels will be 64bits-only. There are some memory and PCI
> > ressources mapped in physical address above 2Gb and so inaccessible from
> > 32bit kernel unmapped segments. It would probably be possible to
> > address this using kernel tlb entries, but it would make things much
> > more complicated, with a posssible run-time cost and no real benefits.
> > N32 binaries run fine, of course (I've not tested N64 yet).
> > 
> > Next, there may be userland compile-time options issues: earlier loongson2f
> > processors needs a workaround in software for processor hang, for both
> > kernel and userland binaries (nop should be remplaced with or at,at,zero,
> > this is what gas' -fix-loongson2f-nop option does. Only earlier loongson2f
> > are affected (mine seems not have this problem) so maybe we can just
> > ignore the issue, or build all evbmips64 binaries with this option
> > (-fix-loongson2f-nop has ~no runtime performance impact, and should
> > have no bad effect on any processor but who knows ...)
> > 
> > loongson2 system use pmon as firmware (http://www.opsycon.se/PMON2000/Main).
> > The pmon version provided by lemote can load ELF files from ext2fs, fat or
> > iso9660; the partition table is fdisk-style (MSDOS).
> > It looks like there's no way to load from other disk format
> > (say, get the first 512 bytes of the disk executed).
> > This mean we have to keep a small ext2 partition at the beggining of drive,
> > which holds the NetBSD kernel or a NetBSD bootloader.
> 
> Can you use a small cd9660 partition at the beginning, instead?  I ask
> because we have cross-tools for creating cd9660 partitions, but not for
> ext2 partitions, so cd9660 is most convenient.

It can probably be done, but it would make updating the kernel or
bootloader of an installed system more difficult. We can do this for
install medias, of course.

> 
> Can pmon boot an ELF kernel from a "special" MBR partition?  I have a
> MIPS board that treats an MBR partition of type 39 as an ELF kernel, but
> I don't know if any other BIOS does that.

I didn't see this in the docs ...

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--