| Message ID | 1253835348-12640-1-git-send-email-khilman@deeprootsystems.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Kevin Hilman |
| Headers | show |
Kevin, On Friday 25 September 2009 01:35:48 Kevin Hilman wrote: > During suspend, the kernel timekeeping subsystem is shut down. Before > suspend and upon resume, it uses a weak function > read_persistent_clock() to determine the amount of time that elapsed > during suspend. > > This function was not implemented on OMAP, so from the timekeeping > subsystem perspective (and thus userspace as well) it appeared that no > time elapsed during suspend. > > This patch uses the 32k sync timer as a the persistent clock the 32k > sync timer value converted to seconds. > > NOTE: This does *NOT* handle wrapping of the 32k sync timer, so > wrapping of the 32k sync timer during suspend may cause > problems. Also, there are not interrupts when the 32k sync > timer wraps, so something else has to be done. I think we should read the 32k timer value before entering the sleep and reading it again at resume time. Doing so up to one overflow could be handled, which means a maximum sleep period of 36.4 hours. Now the time wrap problem imposes the system to wake-up before 36.4 hours. We have a few options: 1) always use the wake-up timer with a wake-up time < 36.4 hours 2) rely on the user space to set the wake-up timer correctly, depending on the applications needs. I am for option 1. Any thoughts? Regards, Jean > > Reported-by: Jon Hunter <jon-hunter@ti.com> > Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com> > --- > Tested on OMAP3 using PM branch. > If no issues, I will queue for 2.6.32-rc fixes > > arch/arm/plat-omap/common.c | 15 +++++++++++++++ > 1 files changed, 15 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c > index b3f70e6..3e4325b 100644 > --- a/arch/arm/plat-omap/common.c > +++ b/arch/arm/plat-omap/common.c > @@ -178,6 +178,21 @@ unsigned long long sched_clock(void) > return ret; > } > > +/** > + * read_persistent_clock - Return time in seconds from the persistent > clock. + */ > +unsigned long read_persistent_clock(void) > +{ > + unsigned long long ret; > + cycle_t cycles; > + > + cycles = clocksource_32k.read(&clocksource_32k); > + ret = (cycles * clocksource_32k.mult_orig) >> clocksource_32k.shift; > + do_div(ret, NSEC_PER_SEC); > + > + return (unsigned long)ret; > +} > + > static int __init omap_init_clocksource_32k(void) > { > static char err[] __initdata = KERN_ERR -- To unsubscribe from this list: send the line "unsubscribe linux-omap" 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/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c index b3f70e6..3e4325b 100644 --- a/arch/arm/plat-omap/common.c +++ b/arch/arm/plat-omap/common.c @@ -178,6 +178,21 @@ unsigned long long sched_clock(void) return ret; } +/** + * read_persistent_clock - Return time in seconds from the persistent clock. + */ +unsigned long read_persistent_clock(void) +{ + unsigned long long ret; + cycle_t cycles; + + cycles = clocksource_32k.read(&clocksource_32k); + ret = (cycles * clocksource_32k.mult_orig) >> clocksource_32k.shift; + do_div(ret, NSEC_PER_SEC); + + return (unsigned long)ret; +} + static int __init omap_init_clocksource_32k(void) { static char err[] __initdata = KERN_ERR
During suspend, the kernel timekeeping subsystem is shut down. Before suspend and upon resume, it uses a weak function read_persistent_clock() to determine the amount of time that elapsed during suspend. This function was not implemented on OMAP, so from the timekeeping subsystem perspective (and thus userspace as well) it appeared that no time elapsed during suspend. This patch uses the 32k sync timer as a the persistent clock the 32k sync timer value converted to seconds. NOTE: This does *NOT* handle wrapping of the 32k sync timer, so wrapping of the 32k sync timer during suspend may cause problems. Also, there are not interrupts when the 32k sync timer wraps, so something else has to be done. Reported-by: Jon Hunter <jon-hunter@ti.com> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com> --- Tested on OMAP3 using PM branch. If no issues, I will queue for 2.6.32-rc fixes arch/arm/plat-omap/common.c | 15 +++++++++++++++ 1 files changed, 15 insertions(+), 0 deletions(-)