Messages in this thread | | | Date | Mon, 23 Dec 2013 11:28:28 -0800 | Subject | Re: [RFC 02/18] power/reset: vexpress: Use sched_clock as the time source | From | John Stultz <> |
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On Mon, Dec 23, 2013 at 8:23 AM, Pawel Moll <pawel.moll@arm.com> 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 <pawel.moll@arm.com> > Cc: Anton Vorontsov <anton@enomsg.org> > Cc: David Woodhouse <dwmw2@infradead.org> > --- > 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.
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)?
thanks -john
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