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    SubjectRe: test version of 2.1.0 available


    I just booted 2.1.0-#4 with mmio for the bsd ncr driver with success.
    For the moment all is ok.

    On Wed, 25 Sep 1996, Linus Torvalds wrote:

    > On Tue, 24 Sep 1996, Gerard Roudier wrote:
    > >
    > > I remember that for high physical address space on i386, readX()/writeX()
    > > won't work and that we must get a virtual address from vremap().
    > Yes.

    But seemed to me that was incorrect since the semantic of readX/writeX
    was memory IO operations at a physical memory address of the bus.

    > > Under ALPHA neither the physical address nor the remapped did work.
    > Under alpha, readb() always works, and remapping is not wanted or even
    > possible (remapping only works for memory accesses, and this is really an IO
    > access).

    Hmmm ...
    I remember that I had sent to Harald a patch that just used the base
    address returned by the pci bios and that did not work.

    > I see now that vremap() was pretty badly designed, but I think I outlined
    > a solution to this all in the previous mail.

    My guess was that the design of vremap() was to remap physical main memory.
    i386 architecture is a special case that throwed confusion.

    > > I understand that now we can use the physical address with all
    > > architectures and that will work like a charm.
    > > I will try that on my pentium tomorrow.

    Dont be afraid, I _never_ intended to do that. :)
    In french, we say about such assertion:
    "Precher le faux pour savoir le vrai".

    > Nope, won't work. You still do need to remap on the x86, simply because the
    > kernel address space cannot contain all of the 4GB PCI io space, only the
    > "low" parts (ie the 640-1MB hole). The problem was a unfortunate interaction
    > between the remap and the read{bwl} access functions.

    Thanks for your explanations. All is now clear for me.
    I looked into #4. "ioremap()" instead of "vremap()" is now clean and there
    is no possible confusion.

    > Anybody with an alpha with a ncr controller wants to test? If you could try
    > the fix outlined in the previous mail to linux-kernel (just make vremap()
    > directly return the argument address on an alpha), and see if memory mapped
    > accesses work on the alpha with the BSD-NCR driver after that I'd be
    > interested to hear about it..

    The ncr driver does lots of 1 byte IO done through sparse space.
    When Harald and I have tried mmio on Alpha, this code seemed untested.

    What have you planned for 2.0.X?
    Is 2.0.21 the last (sub)level of 2.0?

    > Linus

    Sorry for the questions and thanks a lot for starting Linux 2.1.X.


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