| Message ID | 1385420137-32725-1-git-send-email-dianders@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@chromium.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. Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Monday 25 of November 2013 15:23:27 Guenter Roeck 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@chromium.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. Seems like it got renamed to ARM_S3C24XX_CPUFREQ by f023f8dd59. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Guenter, On Mon, Nov 25, 2013 at 3:23 PM, Guenter Roeck <linux@roeck-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@chromium.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-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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@roeck-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@chromium.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 -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Nov 25, 2013 at 02:55:37PM -0800, 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. The S3C2410 to at-least S3C2440 there is only one PLL/clock-divider set so changing any part of that can change frequency supplied to the watchdog. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tuesday 26 of November 2013 00:08:31 Ben Dooks wrote: > On Mon, Nov 25, 2013 at 02:55:37PM -0800, 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. > > The S3C2410 to at-least S3C2440 there is only one PLL/clock-divider > set so changing any part of that can change frequency supplied to > the watchdog. And so we're leaving the notifier code intact, just changing the ifdef conditionm which decides whether it should be compiled in, from a (too) generic one to an S3C24xx-specific one. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 static int s3c2410wdt_cpufreq_transition(struct notifier_block *nb, unsigned long val, void *data)
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@chromium.org> --- drivers/watchdog/s3c2410_wdt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)