[3.16.y-ckt stable] Patch "ARM: 8222/1: mvebu: enable strex backoff delay" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ARM: 8222/1: mvebu: enable strex backoff delay

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt3.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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>From 55c9a74c4d64c1ec1e3dc8aad58b36c71fb51db9 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Date: Tue, 25 Nov 2014 18:43:15 +0100
Subject: ARM: 8222/1: mvebu: enable strex backoff delay

commit 995ab5189d1d7264e79e665dfa032a19b3ac646e upstream.

Under extremely rare conditions, in an MPCore node consisting of at
least 3 CPUs, two CPUs trying to perform a STREX to data on the same
shared cache line can enter a livelock situation.

This patch enables the HW mechanism that overcomes the bug. This fixes
the incorrect setup of the STREX backoff delay bit due to a wrong
description in the specification.

Note that enabling the STREX backoff delay mechanism is done by
leaving the bit *cleared*, while the bit was currently being set by
the proc-v7.S code.

[Thomas: adapt to latest mainline, slightly reword the commit log, add
stable markers.]

Fixes: de4901933f6d ("arm: mm: Add support for PJ4B cpu and init routines")

Signed-off-by: Nadav Haklai <nadavh at marvell.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement at free-electrons.com>
Acked-by: Jason Cooper <jason at lakedaemon.net>
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/arm/mm/proc-v7.S | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 3db2c2f04a30..0eba0d1fd65a 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -235,7 +235,6 @@ __v7_pj4b_setup:
 /* Auxiliary Debug Modes Control 1 Register */
 #define PJ4B_STATIC_BP (1 << 2) /* Enable Static BP */
 #define PJ4B_INTER_PARITY (1 << 8) /* Disable Internal Parity Handling */
-#define PJ4B_BCK_OFF_STREX (1 << 5) /* Enable the back off of STREX instr */
 #define PJ4B_CLEAN_LINE (1 << 16) /* Disable data transfer for clean line */

 /* Auxiliary Debug Modes Control 2 Register */
@@ -258,7 +257,6 @@ __v7_pj4b_setup:
 	/* Auxiliary Debug Modes Control 1 Register */
 	mrc	p15, 1,	r0, c15, c1, 1
 	orr     r0, r0, #PJ4B_CLEAN_LINE
-	orr     r0, r0, #PJ4B_BCK_OFF_STREX
 	orr     r0, r0, #PJ4B_INTER_PARITY
 	bic	r0, r0, #PJ4B_STATIC_BP
 	mcr	p15, 1,	r0, c15, c1, 1