lkml.org 
[lkml]   [2013]   [Dec]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC 02/18] power/reset: vexpress: Use sched_clock as the time source
From
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


\
 
 \ /
  Last update: 2013-12-23 20:41    [W:0.186 / U:1.792 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site