Patch "powerpc: Fix /proc/cpuinfo revision for POWER9 DD2" has been added to the 4.12-stable tree

This is a note to let you know that I've just added the patch titled

powerpc: Fix /proc/cpuinfo revision for POWER9 DD2

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-fix-proc-cpuinfo-revision-for-power9-dd2.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

rom 64ebb9a208c6e66316329a6d9101815d1ee06fa9 Mon Sep 17 00:00:00 2001
From: Michael Neuling <[email protected]>
Date: Thu, 15 Jun 2017 11:53:16 +1000
Subject: powerpc: Fix /proc/cpuinfo revision for POWER9 DD2

From: Michael Neuling <[email protected]>

commit 64ebb9a208c6e66316329a6d9101815d1ee06fa9 upstream.

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.

---
 arch/powerpc/kernel/setup-common.c |    4 ++++
 1 file changed, 4 insertions(+)

@@ -335,6 +335,10 @@ static int show_cpuinfo(struct seq_file
 				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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/powerpc-fix-proc-cpuinfo-revision-for-power9-dd2.patch