linux-kernel - Re: [PATCH] watchdog: s3c2410_wdt: Only register for cpufreq on CPU_FREQ

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAD=FV=WijF-ZyST8p13Rog1VGSx+c-2MES+FpxbSGzd16rAZoA@mail.gmail.com>
Date:	Mon, 25 Nov 2013 15:28:29 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Wim Van Sebroeck <wim@...ana.be>,
	Leela Krishna Amudala <l.krishna@...sung.com>,
	Olof Johansson <olof@...om.net>,
	Tomasz Figa <tomasz.figa@...il.com>,
	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

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.

-Doug
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/