From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: [PATCH 2/4] ARM: OMAP: sched_clock() corrected Date: Wed, 04 Mar 2009 10:27:53 -0800 Message-ID: <20090304182753.27331.99951.stgit@localhost> References: <20090304182342.27331.35004.stgit@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mho-01-bos.mailhop.org ([63.208.196.178]:65058 "EHLO mho-01-bos.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753421AbZCDS15 (ORCPT ); Wed, 4 Mar 2009 13:27:57 -0500 In-Reply-To: <20090304182342.27331.35004.stgit@localhost> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: linux-arm-kernel@lists.arm.linux.org.uk Cc: linux-omap@vger.kernel.org, Aaro Koskinen From: Aaro Koskinen After my OMAP3 board has been running for a while, I'm seeing weird latency traces like this: sh-1574 0d.h2 153us : do_timer (tick_do_update_jiffies64) sh-1574 0d.h2 153us : update_wall_time (do_timer) sh-1574 0d.h2 153us!: omap_32k_read (update_wall_time) sh-1574 0d.h2 1883us : update_xtime_cache (update_wall_time) sh-1574 0d.h2 1883us : clocksource_get_next (update_wall_time) sh-1574 0d.h2 1883us+: _spin_lock_irqsave (clocksource_get_next) and after a while: sh-17818 0d.h3 153us : do_timer (tick_do_update_jiffies64) sh-17818 0d.h3 153us : update_wall_time (do_timer) sh-17818 0d.h3 153us!: omap_32k_read (update_wall_time) sh-17818 0d.h3 1915us : update_xtime_cache (update_wall_time) sh-17818 0d.h3 1915us+: clocksource_get_next (update_wall_time) sh-17818 0d.h3 1945us : _spin_lock_irqsave (clocksource_get_next) Turns out that sched_clock() is using cyc2ns(), which returns NTP adjusted time. The sched_clock() frequency should not be adjusted. The patch deletes omap_32k_ticks_to_nsecs() and rewrites sched_clock() to do the conversion using the constant multiplier. Signed-off-by: Aaro Koskinen Signed-off-by: Tony Lindgren --- arch/arm/plat-omap/common.c | 14 +++++--------- 1 files changed, 5 insertions(+), 9 deletions(-) diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c index 0843b88..6825fbb 100644 --- a/arch/arm/plat-omap/common.c +++ b/arch/arm/plat-omap/common.c @@ -200,20 +200,16 @@ static struct clocksource clocksource_32k = { }; /* - * Rounds down to nearest nsec. - */ -unsigned long long omap_32k_ticks_to_nsecs(unsigned long ticks_32k) -{ - return cyc2ns(&clocksource_32k, ticks_32k); -} - -/* * Returns current time from boot in nsecs. It's OK for this to wrap * around for now, as it's just a relative time stamp. */ unsigned long long sched_clock(void) { - return omap_32k_ticks_to_nsecs(omap_32k_read()); + unsigned long long ret; + + ret = (unsigned long long)omap_32k_read(); + ret = (ret * clocksource_32k.mult_orig) >> clocksource_32k.shift; + return ret; } static int __init omap_init_clocksource_32k(void)