Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752452AbaFDRbE (ORCPT ); Wed, 4 Jun 2014 13:31:04 -0400 Received: from mail-vc0-f201.google.com ([209.85.220.201]:50379 "EHLO mail-vc0-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752387AbaFDRbB (ORCPT ); Wed, 4 Jun 2014 13:31:01 -0400 From: Doug Anderson To: Kukjin Kim , Tomasz Figa Cc: Daniel Lezcano , Vincent Guittot , Chirantan Ekbote , David Riley , olof@lixom.net, linux-samsung-soc@vger.kernel.org, Mandeep Singh Baines , Andrew Bresticker , Doug Anderson , tglx@linutronix.de, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 2/3] clocksource: exynos_mct: cache mct upper count Date: Wed, 4 Jun 2014 10:30:33 -0700 Message-Id: <1401903034-20074-2-git-send-email-dianders@chromium.org> X-Mailer: git-send-email 2.0.0.526.g5318336 In-Reply-To: <1401903034-20074-1-git-send-email-dianders@chromium.org> References: <1401903034-20074-1-git-send-email-dianders@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mandeep Singh Baines Saves one register read. Note that the upper count only changes every ~178 seconds with a 24MHz source clock, so it's likely it hasn't changed from call to call. Before: 1323852 us for 1000000 gettimeofday in userspace After: 1173084 us for 1000000 gettimeofday in userspace Note that even with this change the CPU is in exynos_frc_read() more than 2% of the time in real world profiles of ChromeOS. That indicates that it's important to optimize. Signed-off-by: Mandeep Singh Baines Signed-off-by: Andrew Bresticker Signed-off-by: Doug Anderson --- drivers/clocksource/exynos_mct.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index ba3a683..7cbe4aa 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -167,8 +167,8 @@ static void exynos4_mct_frc_start(u32 hi, u32 lo) static inline cycle_t notrace _exynos4_frc_read(void) { - unsigned int lo, hi; - u32 hi2 = __raw_readl(reg_base + EXYNOS4_MCT_G_CNT_U); + u32 lo, hi; + static u32 hi2; do { hi = hi2; -- 2.0.0.526.g5318336 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/