[PATCH] powerpc: Fix /proc/cpuinfo revision for POWER9 DD2

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[PATCH] powerpc: Fix /proc/cpuinfo revision for POWER9 DD2

Michael Neuling-2
The P9 PVR bits 12-15 don't indicate a revision but instead different
chip configurations.  From BookIV we have:
   Bits      Configuration
    0 :    Scale out 12 cores
    1 :    Scale out 24 cores
    2 :    Scale up  12 cores
    3 :    Scale up  24 cores

DD1 doesn't use this but DD2 does. Linux will mostly use the "Scale
out 24 core" configuration (ie. SMT4 not SMT8) which results in a PVR
of 0x004e1200. The reported revision in /proc/cpuinfo is hence
reported incorrectly as "18.0".

This patch fixes this to mask off only the relevant bits for the major
revision (ie. bits 8-11) for POWER9.

Signed-off-by: Michael Neuling <[hidden email]>
---
 arch/powerpc/kernel/setup-common.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 857129acf9..94a948207c 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -335,6 +335,10 @@ static int show_cpuinfo(struct seq_file *m, void *v)
  maj = ((pvr >> 8) & 0xFF) - 1;
  min = pvr & 0xFF;
  break;
+ case 0x004e: /* POWER9 bits 12-15 give chip type */
+ maj = (pvr >> 8) & 0x0F;
+ min = pvr & 0xFF;
+ break;
  default:
  maj = (pvr >> 8) & 0xFF;
  min = pvr & 0xFF;
--
2.11.0

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Re: powerpc: Fix /proc/cpuinfo revision for POWER9 DD2

Michael Ellerman-3
On Thu, 2017-06-15 at 01:53:16 UTC, Michael Neuling wrote:

> The P9 PVR bits 12-15 don't indicate a revision but instead different
> chip configurations.  From BookIV we have:
>    Bits      Configuration
>     0 :    Scale out 12 cores
>     1 :    Scale out 24 cores
>     2 :    Scale up  12 cores
>     3 :    Scale up  24 cores
>
> DD1 doesn't use this but DD2 does. Linux will mostly use the "Scale
> out 24 core" configuration (ie. SMT4 not SMT8) which results in a PVR
> of 0x004e1200. The reported revision in /proc/cpuinfo is hence
> reported incorrectly as "18.0".
>
> This patch fixes this to mask off only the relevant bits for the major
> revision (ie. bits 8-11) for POWER9.
>
> Signed-off-by: Michael Neuling <[hidden email]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/64ebb9a208c6e66316329a6d910181

cheers