linux-kernel - [PATCH] ARM: exynos: mct: cache mct upper count

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Message-Id: <1346880973-31519-1-git-send-email-msb@chromium.org>
Date:	Wed,  5 Sep 2012 14:36:13 -0700
From:	Mandeep Singh Baines <msb@...omium.org>
To:	Kukjin Kim <kgene.kim@...sung.com>, linux-kernel@...r.kernel.org
Cc:	Mandeep Singh Baines <msb@...omium.org>,
	Sonny Rao <sonnyrao@...omium.org>,
	Olof Johansson <olofj@...omium.org>,
	Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org
Subject: [PATCH] ARM: exynos: mct: cache mct upper count

Saves one register read.

Before (perf report):

     1.40%  [k] exynos4_frc_read
            |
            |--87.20%-- ktime_get_ts
            |          |
            |          |--93.60%-- posix_ktime_get_ts

After (perf report):

     1.00%  [k] exynos4_frc_read
            |
            |--88.61%-- ktime_get_ts
            |          |
            |          |--92.70%-- posix_ktime_get_ts

Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
CC: Sonny Rao <sonnyrao@...omium.org>
CC: Olof Johansson <olofj@...omium.org>
CC: Kukjin Kim <kgene.kim@...sung.com>
CC: Russell King <linux@....linux.org.uk>
CC: linux-arm-kernel@...ts.infradead.org
CC: linux-samsung-soc@...r.kernel.org
---
 arch/arm/mach-exynos/mct.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-exynos/mct.c b/arch/arm/mach-exynos/mct.c
index b601fb8..2bbd533 100644
--- a/arch/arm/mach-exynos/mct.c
+++ b/arch/arm/mach-exynos/mct.c
@@ -128,8 +128,8 @@ static void exynos4_mct_frc_start(u32 hi, u32 lo)
 
 static cycle_t exynos4_frc_read(struct clocksource *cs)
 {
-	unsigned int lo, hi;
-	u32 hi2 = __raw_readl(EXYNOS4_MCT_G_CNT_U);
+	u32 lo, hi;
+	static u32 hi2;
 
 	do {
 		hi = hi2;
-- 
1.7.7.3

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