From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Sun, 22 Nov 2009 20:03:37 +0100 (CET) Received: from gateway-1237.mvista.com ([206.112.117.35]:26848 "HELO imap.sh.mvista.com" rhost-flags-OK-OK-OK-FAIL) by ftp.linux-mips.org with SMTP id S1492870AbZKVTDa (ORCPT ); Sun, 22 Nov 2009 20:03:30 +0100 Received: from [127.0.0.1] (unknown [10.150.0.9]) by imap.sh.mvista.com (Postfix) with SMTP id B3DCF3EC9; Sun, 22 Nov 2009 11:03:13 -0800 (PST) Message-ID: <4B098AE4.6090804@ru.mvista.com> Date: Sun, 22 Nov 2009 22:03:00 +0300 From: Sergei Shtylyov User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) MIME-Version: 1.0 To: Wu Zhangjin Cc: Ralf Baechle , Ingo Molnar , Thomas Gleixner , linux-mips@linux-mips.org, Michal Simek Subject: Re: [PATCH v3] MIPS: Add a high resolution sched_clock() via cnt32_to_63(). References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 25040 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: sshtylyov@ru.mvista.com Precedence: bulk X-list: linux-mips Hello. Wu Zhangjin wrote: > From: Wu Zhangjin > > (This v3 revision incorporates with the feedbacks from Ingo, Ralf and Sergei.) > > This patch adds a cnt32_to_63() and MIPS c0 count based sched_clock(), > which provides high resolution. and also, one new kernel option > (HR_SCHED_CLOCK) is added to enable/disable this sched_clock(). > > Without it, the Ftrace for MIPS will give useless timestamp information. > > Because cnt32_to_63() needs to be called at least once per half period > to work properly, Differ from the old version, this v2 revision set up a > kernel timer to ensure the requirement of some MIPSs which have short c0 > count period. > > Signed-off-by: Wu Zhangjin > --- > arch/mips/Kconfig | 18 ++++++++++++++ > arch/mips/kernel/csrc-r4k.c | 55 +++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 73 insertions(+), 0 deletions(-) > > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig > index b342197..5ea55f5 100644 > --- a/arch/mips/Kconfig > +++ b/arch/mips/Kconfig > @@ -1952,6 +1952,24 @@ config NR_CPUS > source "kernel/time/Kconfig" > > # > +# High Resolution sched_clock() Configuration > +# > + > +config HR_SCHED_CLOCK > + bool "High Resolution sched_clock()" > + depends on CSRC_R4K > + default n > + help > + This option enables the MIPS c0 count based high resolution > + sched_clock(). > + > + If you need a ns precision timestamp, you are recommended to enable > + this option. For example, If you are using the Ftrace subsystem to do > + real time tracing, this option is needed. > + > + If unsure, disable it. > + > +# > # Timer Interrupt Frequency Configuration > # > > diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c > index e95a3cd..e287f0d 100644 > --- a/arch/mips/kernel/csrc-r4k.c > +++ b/arch/mips/kernel/csrc-r4k.c > @@ -10,6 +10,57 @@ > > #include > > +#ifdef CONFIG_HR_SCHED_CLOCK > +#include > +#include > + > +/* > + * MIPS sched_clock implementation. > + * > + * because cnt32_to_63() needs to be called at least once per half period to > + * work properly, and some of the MIPS frequency is high, perhaps a kernel > + * timer is needed to be set up to ensure this requirement is always met. > + * Please refer to arch/arm/plat-orion/time.c and include/linux/cnt32_to_63.h > + */ > +static unsigned long __read_mostly tclk2ns_scale; > +static unsigned long __read_mostly tclk2ns_scale_factor; > + > +unsigned long long notrace sched_clock(void) > +{ > + unsigned long long v = cnt32_to_63(read_c0_count()); > + return (v * tclk2ns_scale) >> tclk2ns_scale_factor; > +} > + > +static struct timer_list cnt32_to_63_keepwarm_timer; > + > +static void cnt32_to_63_keepwarm(unsigned long data) > +{ > + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); > + (void) sched_clock(); > +} > + > +static void __init setup_sched_clock(struct clocksource *cs, unsigned long tclk) > +{ > + unsigned long long v; > + unsigned long data; > + > + v = cs->mult; > + /* > + * We want an even value to automatically clear the top bit > + * returned by cnt32_to_63() without an additional run time > + * instruction. So if the LSB is 1 then round it up. > + */ > + if (v & 1) > + v++; > + tclk2ns_scale = v; > + tclk2ns_scale_factor = cs->shift; > + > + data = 0x80000000 / tclk * HZ; > + setup_timer(&cnt32_to_63_keepwarm_timer, cnt32_to_63_keepwarm, data); > + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); > +} > +#endif /* !CONFIG_HR_SCHED_CLOCK */ > + > static cycle_t c0_hpt_read(struct clocksource *cs) > { > return read_c0_count(); > @@ -32,6 +83,10 @@ int __init init_r4k_clocksource(void) > > clocksource_set_clock(&clocksource_mips, mips_hpt_frequency); > > +#ifdef CONFIG_HR_SCHED_CLOCK > + setup_sched_clock(&clocksource_mips, mips_hpt_frequency); > +#endif > + > According to CodingStyle #ifdef's in the code are frowned upon. I suggest that you add an empty setup_sched_clock() definition under #else above and have the call here without #ifdef. That's the preferred way of doing such things... WBR, Sergei