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Message-ID: <3917232.5usgOlQl6Q@flatron>
Date: Tue, 26 Nov 2013 00:31:30 +0100
From: Tomasz Figa <tomasz.figa@...il.com>
To: Doug Anderson <dianders@...omium.org>
Cc: Guenter Roeck <linux@...ck-us.net>,
Wim Van Sebroeck <wim@...ana.be>,
Leela Krishna Amudala <l.krishna@...sung.com>,
Olof Johansson <olof@...om.net>,
Kukjin Kim <kgene.kim@...sung.com>,
Ben Dooks <ben-linux@...ff.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
linux-watchdog@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] watchdog: s3c2410_wdt: Only register for cpufreq on CPU_FREQ_S3C24XX
On Monday 25 of November 2013 15:28:29 Doug Anderson wrote:
> Guenter,
>
> On Mon, Nov 25, 2013 at 3:23 PM, Guenter Roeck <linux@...ck-us.net> wrote:
> > On 11/25/2013 02:55 PM, Doug Anderson wrote:
> >>
> >> On modern SoCs the watchdog timer is parented on a clock that doesn't
> >> change every time we have a cpufreq change. That means we don't need
> >> to constantly adjust the watchdog timer, so avoid registering for and
> >> dealing with cpufreq transitions unless we've actually got
> >> CPU_FREQ_S3C24XX defined.
> >>
> >> Note that this is more than just an optimization. The s3c2410
> >> watchdog driver actually pats the watchdog on every CPU frequency
> >> change. On modern systems these happen many times per second (even in
> >> a system where "nothing" is happening). That effectively makes any
> >> userspace watchdog program useless (the watchdog is constantly patted
> >> by the kernel). If we need CPU_FREQ_S3C24XX defined on a
> >> multiplatform kernel we'll need to make sure that kernel supports
> >> common clock and change this to user common clock framework.
> >>
> >> Signed-off-by: Doug Anderson <dianders@...omium.org>
> >> ---
> >> drivers/watchdog/s3c2410_wdt.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/watchdog/s3c2410_wdt.c
> >> b/drivers/watchdog/s3c2410_wdt.c
> >> index 7d8fd04..4980f84 100644
> >> --- a/drivers/watchdog/s3c2410_wdt.c
> >> +++ b/drivers/watchdog/s3c2410_wdt.c
> >> @@ -264,7 +264,7 @@ static irqreturn_t s3c2410wdt_irq(int irqno, void
> >> *param)
> >> return IRQ_HANDLED;
> >> }
> >>
> >> -#ifdef CONFIG_CPU_FREQ
> >> +#ifdef CONFIG_CPU_FREQ_S3C24XX
> >>
> > Where is the CPU_FREQ_S3C24XX configuration option defined ? I don't see it
> > in the current upstream kernel, so it appears that this depends on some
> > out-of-tree changes.
>
> Whoops! I guess I just trusted another patch and didn't dig. I was
> basing this on https://patchwork.kernel.org/patch/3023421/
>
> Ah, I see that Tomasz just found the answer. I'll update my patch.
Seems like I originally gave you the wrong symbol name, looking at our
internal 3.10 tree, where the rename is not present yet, and nobody
noticed. Sorry for that.
Best regards,
Tomasz
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