Re: loongson2f: evbmips or new port ?

[David Young <dyoung%pobox.com@localhost>]

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.

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.

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 344-0444 x24