linux-kernel - [PATCH AUTOSEL for 3.18 049/101] powerpc: Fix /proc/cpuinfo revision for POWER9 DD2

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Date:   Mon, 9 Apr 2018 00:35:59 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Michael Neuling <mikey@...ling.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 3.18 049/101] powerpc: Fix /proc/cpuinfo revision
 for POWER9 DD2

From: Michael Neuling <mikey@...ling.org>

[ Upstream commit 64ebb9a208c6e66316329a6d9101815d1ee06fa9 ]

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 <mikey@...ling.org>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 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 1362cd62b3fa..01b2950273cb 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -310,6 +310,10 @@ 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;
-- 
2.15.1