| Message ID | 1385422603-22684-1-git-send-email-dianders@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Monday 25 of November 2013 15:36:43 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 > CONFIG_ARM_S3C24XX_CPUFREQ 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 ARM_S3C24XX_CPUFREQ 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> > --- > Changes in v2: > - Use the updated config name. > > drivers/watchdog/s3c2410_wdt.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Tomasz Figa <t.figa@samsung.com> Best regards, Tomasz
On 11/25/2013 03:36 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 > CONFIG_ARM_S3C24XX_CPUFREQ 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 ARM_S3C24XX_CPUFREQ 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> Reviewed-by: Guenter Roeck <linux@roeck-us.net>
diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c index 7d8fd04..c1ada33 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_ARM_S3C24XX_CPUFREQ 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 CONFIG_ARM_S3C24XX_CPUFREQ 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 ARM_S3C24XX_CPUFREQ 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> --- Changes in v2: - Use the updated config name. drivers/watchdog/s3c2410_wdt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)