From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752691AbbKYQGY (ORCPT ); Wed, 25 Nov 2015 11:06:24 -0500 Received: from mx0b-0016f401.pphosted.com ([67.231.156.173]:33424 "EHLO mx0b-0016f401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751403AbbKYQFv (ORCPT ); Wed, 25 Nov 2015 11:05:51 -0500 From: Jisheng Zhang To: , , CC: , , Jisheng Zhang Subject: [PATCH v4 2/2] clocksource/drivers/dw_apb_timer: Use {readl|writel}_relaxed in critical path Date: Thu, 26 Nov 2015 00:01:53 +0800 Message-ID: <1448467313-5626-3-git-send-email-jszhang@marvell.com> X-Mailer: git-send-email 2.6.2 In-Reply-To: <1448467313-5626-1-git-send-email-jszhang@marvell.com> References: <1448467313-5626-1-git-send-email-jszhang@marvell.com> MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2015-11-25_11:,, 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-1511250281 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It's safe to use the relaxed version. From another side, the relaxed io accessor macros are available on all architectures now, so we can use the relaxed versions to get a trivial system performance improvement, we measured time the following functions spent on Marvell BG4CT: 4096 rounds of __apbt_read_clocksource() call: before the patch: 1263240ns on average after the patch: 1250080ns on average improved by 1% 4096 rounds of apbt_eoi() call: before the patch: 1290960ns on average after the patch: 1248240ns on average 4096 rounds of apbt_next_event() call: before the patch: 3333660ns on average after the patch: 1322040ns on average improved by 60%! Signed-off-by: Jisheng Zhang --- drivers/clocksource/dw_apb_timer.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/clocksource/dw_apb_timer.c b/drivers/clocksource/dw_apb_timer.c index 114696b..6334526 100644 --- a/drivers/clocksource/dw_apb_timer.c +++ b/drivers/clocksource/dw_apb_timer.c @@ -60,6 +60,17 @@ static inline void apbt_writel(struct dw_apb_timer *timer, u32 val, writel(val, timer->base + offs); } +static inline u32 apbt_readl_relaxed(struct dw_apb_timer *timer, unsigned long offs) +{ + return readl_relaxed(timer->base + offs); +} + +static inline void apbt_writel_relaxed(struct dw_apb_timer *timer, u32 val, + unsigned long offs) +{ + writel_relaxed(val, timer->base + offs); +} + static void apbt_disable_int(struct dw_apb_timer *timer) { u32 ctrl = apbt_readl(timer, APBTMR_N_CONTROL); @@ -81,7 +92,7 @@ void dw_apb_clockevent_pause(struct dw_apb_clock_event_device *dw_ced) static void apbt_eoi(struct dw_apb_timer *timer) { - apbt_readl(timer, APBTMR_N_EOI); + apbt_readl_relaxed(timer, APBTMR_N_EOI); } static irqreturn_t dw_apb_clockevent_irq(int irq, void *data) @@ -200,13 +211,13 @@ static int apbt_next_event(unsigned long delta, struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt); /* Disable timer */ - ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL); + ctrl = apbt_readl_relaxed(&dw_ced->timer, APBTMR_N_CONTROL); ctrl &= ~APBTMR_CONTROL_ENABLE; - apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL); + apbt_writel_relaxed(&dw_ced->timer, ctrl, APBTMR_N_CONTROL); /* write new count */ - apbt_writel(&dw_ced->timer, delta, APBTMR_N_LOAD_COUNT); + apbt_writel_relaxed(&dw_ced->timer, delta, APBTMR_N_LOAD_COUNT); ctrl |= APBTMR_CONTROL_ENABLE; - apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL); + apbt_writel_relaxed(&dw_ced->timer, ctrl, APBTMR_N_CONTROL); return 0; } @@ -342,7 +353,8 @@ static cycle_t __apbt_read_clocksource(struct clocksource *cs) struct dw_apb_clocksource *dw_cs = clocksource_to_dw_apb_clocksource(cs); - current_count = apbt_readl(&dw_cs->timer, APBTMR_N_CURRENT_VALUE); + current_count = apbt_readl_relaxed(&dw_cs->timer, + APBTMR_N_CURRENT_VALUE); return (cycle_t)~current_count; } -- 2.6.2