RE: dcbz works on 862 everywhere!

Joakim Tjernlund wrote:

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Hi list

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 I even
removed the TLB change bit hack by Tom Rini and everything works.

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I removed the "copy DAR to MD_EPN" part in the DTLB Error handler and my systems
runs fine.

How exactly do you know that "everything works fine" ???

Please note that

    a) you may have bug-free hardware.
    b) you may have a valid TLB entry at the time 'dcbz' is executed.
    c) you may end up with a bogus mapping but not notice it.

Every time I tried to use dcbz on user space it failed HARD directly.
Whenever I tried to "undo" any hacks that were there to compensate for
buggy dcxx instructions, the kernel would not boot.

Now I can boot and run my app and even run a user space app which clears
memory with dcbz. I can remove HWWRITE bit setting on kernel space address and
remove the copying of DAR to MD_EPN in the DTLB Error handler.

I think I am on to something here, don't you?

You really should first confirm that your hardware suffers from the bug by
running a _simple_ test program in a _simple_ environment (NOT linux).

I don't have a simple environment. I have ppcboot on my board which doesn't
use the MMU at all.

Then, you should confirm that your workaround solution is correct by
testing it in the same simple environment.

Just because you are able to use 'dcbz' on linux repeatedly without
crashing does'nt prove that your hardware is buggy but linux handles
it correctly.

Yes, I know that and that's why I write to this list to seek input from
others that know more than I do and have a simple test environment(hint, hint :-)

-- Till

PS: please CC me on any replies; I'm not subscribed to this list

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  Jocke

 Jocke


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