bbram access problems

Tobias Otto-Adamczak toa at
Thu Dec 12 08:54:28 EST 2002

Hi Geoffroy,

> We're trying to use BBRAM on a VersaLogic VSBC-6 m-b.  We use the slram
> driver and the 2.4.18 kernel.  The problem is that we can't acces the
> entire memory of the BBRAM, just the first 64k page.

Where do you know ?

[I just had a quick look into the VSBC-6 manual, for curiosity]
Do you have r/w access to the "Map and Paging Control Register"  where
BBRAM pages are selected ?

> Other problem: we added to our lilo.conf:
> append="slram=BBRAM,0xE0000,+0x10000"

looks okay.

> We can write to the BBRAM but we noticed data corruption (not write
> operation was done) in this address range.  Is there a way to lock this
> memory area?  Is this the right thing to do?

Locking would be an useful idea if you suspect that other processes try
to access it, too. Is this the case ?

> What we need is to mount a filesystem on the entire BBRAM, not just the
> first 64k.

The standard slram driver does only work with a contiguous region of
ram. But you have only a ram window and a some page select bits in an
I/O register. You have to hack the driver code (slram.c), I think. (I am
no expert.)


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