From: Baruch Siach <baruch@tkos.co.il>
To: John Stultz <john.stultz@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Jamie Iles <jamie@jamieiles.com>,
Dinh Nguyen <dinguyen@altera.com>
Subject: Re: [RFC PATCH 2/2] clocksource: dw_apb: allow build for architectures other than arm
Date: Thu, 30 May 2013 08:32:33 +0300 [thread overview]
Message-ID: <20130530053233.GL25186@sapphire.tkos.co.il> (raw)
In-Reply-To: <51A51271.2070506@linaro.org>
Hi John,
On Tue, May 28, 2013 at 01:24:17PM -0700, John Stultz wrote:
> On 05/26/2013 05:12 AM, Baruch Siach wrote:
> >ARM is the only architecture providing sched_clock.h and setup_sched_clock().
> >Implement sched_clock() for use by other architectures.
> >
> >Cc: Ingo Molnar <mingo@redhat.com>
> >Cc: Peter Zijlstra <peterz@infradead.org>
> >Cc: John Stultz <john.stultz@linaro.org>
> >Cc: Thomas Gleixner <tglx@linutronix.de>
> >Cc: Jamie Iles <jamie@jamieiles.com>
> >Cc: Dinh Nguyen <dinguyen@altera.com>
> >Signed-off-by: Baruch Siach <baruch@tkos.co.il>
> >---
[snip]
> >@@ -73,6 +77,9 @@ static void add_clocksource(struct device_node
> > *source_timer)
> > }
> > static void __iomem *sched_io_base;
> >+#ifndef CONFIG_HAVE_SETUP_SCHED_CLOCK
> >+static u64 sched_clock_mult __read_mostly;
> >+#endif
> > static u32 read_sched_clock(void)
> > {
> >@@ -97,7 +104,11 @@ static void init_sched_clock(void)
> > timer_get_base_and_rate(sched_timer, &sched_io_base, &rate);
> > of_node_put(sched_timer);
> >+#ifdef CONFIG_HAVE_SETUP_SCHED_CLOCK
> > setup_sched_clock(read_sched_clock, 32, rate);
> >+#else
> >+ sched_clock_mult = NSEC_PER_SEC / rate;
> >+#endif
> > }
>
> Can you rework this to not use #ifdefs within the function? They
> make it annoying to read the code.
>
> Instead maybe have a local setup_sched_clock() function that sets
> the mult value for the !CONFIG_HAVE_SETUP_SCHED_CLOCK case?
>
> > static const struct of_device_id osctimer_ids[] __initconst = {
> >@@ -124,3 +135,10 @@ void __init dw_apb_timer_init(void)
> > init_sched_clock();
> > }
> >+
> >+#ifndef CONFIG_HAVE_SETUP_SCHED_CLOCK
> >+unsigned long long notrace sched_clock()
> >+{
> >+ return read_sched_clock() * sched_clock_mult;
> >+}
> >+#endif
>
> Also, can you try to condense the number of #ifndef
> CONFIG_HAVE_SETUP_SCHED_CLOCK checks to one, and consolidate the
> needed functions all in that one conditional?
Thanks for your comments. I'll rework the patch and resubmit.
I've just noticed that I have a bigger problem. read_sched_clock() returns
u32, not u64. This means that in a rate of, say, 100MHz it will wrap around
after a little more than 40 seconds. Would it make sense to put ARM's 32 bin
sched_clock extension code (arch/arm/kernel/sched_clock.c) is a common place
(maybe drivers/clocksource), and use that? There seems to be nothing ARM
specific in this code, after all.
baruch
--
http://baruch.siach.name/blog/ ~. .~ Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
- baruch@tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -
next prev parent reply other threads:[~2013-05-30 5:32 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-26 12:12 [RFC PATCH 2/2] clocksource: dw_apb: allow build for architectures other than arm Baruch Siach
2013-05-28 20:24 ` John Stultz
2013-05-30 5:32 ` Baruch Siach [this message]
2013-05-30 16:11 ` John Stultz
2013-05-31 5:32 ` Baruch Siach
2013-06-20 14:44 ` Pavel Machek
2013-06-20 15:03 ` Baruch Siach
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130530053233.GL25186@sapphire.tkos.co.il \
--to=baruch@tkos.co.il \
--cc=dinguyen@altera.com \
--cc=jamie@jamieiles.com \
--cc=john.stultz@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).