From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751675AbbKZMYy (ORCPT ); Thu, 26 Nov 2015 07:24:54 -0500 Received: from mx0b-0016f401.pphosted.com ([67.231.156.173]:4155 "EHLO mx0b-0016f401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750930AbbKZMYw (ORCPT ); Thu, 26 Nov 2015 07:24:52 -0500 From: Jisheng Zhang To: , , , , , CC: , , , Jisheng Zhang Subject: [PATCH v2] clockevents/drivers/arm_global_timer: Use writel_relaxed in gt_compare_set Date: Thu, 26 Nov 2015 20:20:38 +0800 Message-ID: <1448540438-7028-1-git-send-email-jszhang@marvell.com> X-Mailer: git-send-email 2.6.2 MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2015-11-26_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=inbound_notspam policy=inbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1507310000 definitions=main-1511260215 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use the relaxed version to improve performance. we measured time of 4096 rounds of gt_compare_set() spent on Marvell BG2Q: before the patch: 3690648ns on average after the patch: 1083023ns on average improved by 70%! Signed-off-by: Jisheng Zhang --- since v1: - only use relaxed io in gt_compare_set(), this function is the remaining hot code path. - Add performance numbers in commit msg. drivers/clocksource/arm_global_timer.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c index a2cb6fa..f99be6b 100644 --- a/drivers/clocksource/arm_global_timer.c +++ b/drivers/clocksource/arm_global_timer.c @@ -99,17 +99,17 @@ static void gt_compare_set(unsigned long delta, int periodic) counter += delta; ctrl = GT_CONTROL_TIMER_ENABLE; - writel(ctrl, gt_base + GT_CONTROL); - writel(lower_32_bits(counter), gt_base + GT_COMP0); - writel(upper_32_bits(counter), gt_base + GT_COMP1); + writel_relaxed(ctrl, gt_base + GT_CONTROL); + writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0); + writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1); if (periodic) { - writel(delta, gt_base + GT_AUTO_INC); + writel_relaxed(delta, gt_base + GT_AUTO_INC); ctrl |= GT_CONTROL_AUTO_INC; } ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE; - writel(ctrl, gt_base + GT_CONTROL); + writel_relaxed(ctrl, gt_base + GT_CONTROL); } static int gt_clockevent_shutdown(struct clock_event_device *evt) -- 2.6.2