leroy christophe [off-list ref] wrote on 2013/10/15 18:27:00:

=20
=20
Le 11/10/2013 17:13, Joakim Tjernlund a =E9crit :

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"Linuxppc-dev"
[off-list ref]
wrote on 2013/10/11 14:56:40:

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Activating CONFIG=5FPIN=5FTLB allows access to the 24 first Mbytes of =

memory

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at

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bootup instead of 8. It is needed for "big" kernels for instance when

activating

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CONFIG=5FLOCKDEP=5FSUPPORT. This needs to be taken into account in=20

init=5F32

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too,

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otherwise memory allocation soon fails after startup.

Signed-off-by: Christophe Leroy <redacted>

diff -ur linux-3.11.org/arch/powerpc/kernel/head=5F8xx.S

linux-3.11/arch/powerpc/kernel/head=5F8xx.S

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--- linux-3.11.org/arch/powerpc/mm/init=5F32.c   2013-09-02

22:46:10.000000000 +0200

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+++ linux-3.11/arch/powerpc/mm/init=5F32.c   2013-09-09=20

11:28:54.000000000

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+0200

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@@ -213,7 +213,12 @@
      */
     BUG=5FON(first=5Fmemblock=5Fbase !=3D 0);

+#ifdef CONFIG=5FPIN=5FTLB
+   /* 8xx can only access 24MB at the moment */
+   memblock=5Fset=5Fcurrent=5Flimit(min=5Ft(u64, first=5Fmemblock=5Fs=

ize,

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0x01800000));

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+#else
     /* 8xx can only access 8MB at the moment */
     memblock=5Fset=5Fcurrent=5Flimit(min=5Ft(u64, first=5Fmemblock=5F=

size,

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0x00800000));

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+#endif
  }
  #endif /* CONFIG=5F8xx */

hmm, I think you should always map 24 MB (or less if RAM < 24 MB) and=20

do

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the same
in head=5F8xx.S.

Or to keep it simple, just always map at least 16 MB here and in
head=5F8xx.S, assuming
that 16 MB is min RAM for any 8xx system running 3.x kernels.

Yes we could do a more elaborated modification in the future. However it =

also has an impact on the boot loader, so I'm not sure we should make it =

the default without thinking twice.
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In the meantime, my patch does take into account the existing situation=20
where you have 8Mb by default and 24Mb when you activate CONFIG=5FPIN=5FT=

LB.

I see it as a bug fix and I believe we should include it at least in=20
order to allow including in the stable releases.
=20
Do you see any issue with this approach ?

Not at all, so:
Acked-by: Joakim Tjernlund <redacted>