From: Will Deacon <will.deacon@arm.com>
Date: Tue, 6 Mar 2012 16:34:22 +0000 (+0100)
Subject: ARM: 7355/1: perf: clear overflow flag when disabling counter on ARMv7 PMU
X-Git-Tag: v3.2.10~29
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=075964ad4370162964f41ba1136b8581ab1a302a;p=karo-tx-linux.git

ARM: 7355/1: perf: clear overflow flag when disabling counter on ARMv7 PMU

commit 99c1745b9c76910e195889044f914b4898b7c9a5 upstream.

When disabling a counter on an ARMv7 PMU, we should also clear the
overflow flag in case an overflow occurred whilst stopping the counter.
This prevents a spurious overflow being picked up later and leading to
either false accounting or a NULL dereference.

Reported-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index a1f9a627a253..c63934294e07 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -878,6 +878,11 @@ static inline int armv7_pmnc_disable_intens(int idx)
 
 	counter = ARMV7_IDX_TO_COUNTER(idx);
 	asm volatile("mcr p15, 0, %0, c9, c14, 2" : : "r" (BIT(counter)));
+	isb();
+	/* Clear the overflow flag in case an interrupt is pending. */
+	asm volatile("mcr p15, 0, %0, c9, c12, 3" : : "r" (BIT(counter)));
+	isb();
+
 	return idx;
 }