Re: Going from 2.2.12 to 2.2.17pre10

[Michael Lundkvist <ml@epact.se>]

Gabriel Paubert <paubert@iram.es> writes:


> Mine cannot read from disk (for now). With OF it would be easy to call
> methods to read from a disk, but with PPCBUG you woule have either:
>
> - to use firmware specific calls (provided the interface is supported) and
> you don't switch the MMU on (even mapped 1:1) since it does not work
> whatever the documentation claims (actually I think I know where the bug
> is in PPCBUG).
>
> - to write your own drivers for the bootloader (might be quite simple
> actually, since performance is not a concern, and you only need to read).
> But then you have to know where to stop (include readonly filesystems ?).
>
> So for now the (compressed) kernel is always in the initially loaded
> image (very handy for network boots which is what I mostly use).
>

I have to be able to create a standalone system so network boot is not
an option.

Maybe I'll look in to creating a driver for the bootloader. When I get
some spare time....

How portable is something like Grub? Maybe that could be a way to go.

>
> Note that thiss was for 2.2.12, as I said I've not booted 2.2.16 so I did
> not put the patches on my ftp site (that's the only QA I do :-)).
>

OK. 2.2.12 is not interesting. I don't want do reinstall again... :)

>
> Ok, since the main difference is the host bridge. I would rather suspect a
> bad bit setting which results in coherency problems, or bad
> memory/whatever (did you try several MVME2400 to see whether it was
> reproducible ?)
>

I have tried two MVME-2400 boards but I haven't had time to do any
systematic testing. It always crashes in find_buffer in fs/buffer.c
during moderate to heavy disk activity. I'm starting to suspect that
the CMD646 isn't being setup correctly since it feels like the system
was more stable after a cold reboot. I'll have to test it a bit more.

>
> It should be but I don't know how. I implemented the capability to reset
> the VME bus in my Universe driver and tested it on an Pentium VME board
> but right now it is disabled since the driver is compiled by default with
> #define SUICIDAL_VME_RESET.
>
> Trying to modify such a multilayer board with connections to a BGA is a
> daunting prospect. The VME bus buffers might be te right place to do it
> since they should be more or less accessible (with extreme care).
>
> 	Gabriel.

You're probably right that it's easier modify the backplane.

I'll just tell our HW-guys what I want and let them figure it out.

/Micke

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