On Mon, 2013-12-23 at 19:28 +0000, John Stultz wrote: > On Mon, Dec 23, 2013 at 8:23 AM, Pawel Moll <[email protected]> wrote: > > At this stage of system shutdown procedure the jiffies may > > not be updated anymore, so have to base on raw sched_clock > > values. > > > > Signed-off-by: Pawel Moll <[email protected]> > > Cc: Anton Vorontsov <[email protected]> > > Cc: David Woodhouse <[email protected]> > > --- > > drivers/power/reset/vexpress-poweroff.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/power/reset/vexpress-poweroff.c > > b/drivers/power/reset/vexpress-poweroff.c > > index 476aa49..d752233 100644 > > --- a/drivers/power/reset/vexpress-poweroff.c > > +++ b/drivers/power/reset/vexpress-poweroff.c > > @@ -15,6 +15,7 @@ > > #include <linux/of.h> > > #include <linux/of_device.h> > > #include <linux/platform_device.h> > > +#include <linux/sched.h> > > #include <linux/stat.h> > > #include <linux/vexpress.h> > > > > @@ -27,12 +28,12 @@ static void vexpress_reset_do(struct device *dev, const > > char *what) > > vexpress_config_func_get_by_dev(dev); > > > > if (func) { > > - unsigned long timeout; > > + unsigned long long timeout_ns; > > > > err = vexpress_config_write(func, 0, 0); > > > > - timeout = jiffies + HZ; > > - while (time_before(jiffies, timeout)) > > + timeout_ns = sched_clock() + 50000000; > > + while (!err && time_before64(sched_clock(), timeout_ns)) > > cpu_relax(); > > } > > So this may not be a problem in this particular case, but sched_clock > could be backed by jiffies on some hardware, causing the same problem > to appear.
Uh, right. As you guessed, on vexpress sched_clock, once registered, is always available. But of course I shouldn't fully rely on this. > Might udelay/mdelay be a better fit for this sort of case (since > udelay may be counter backed, but may also be loop backed on hardware > without continuous counters)? I'm sure I though about udelay, but for some reason decided against it. The reason may be already invalid, so I'll check it again :-) Thanks! Paweł -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
