Re: [PATCH v5 3/3] PM/runtime:Replace jiffies based accounting with ktime based accounting

[Guenter Roeck]

On 1/18/19 2:42 AM, Vincent Guittot wrote:
> Hi Guenter,
>
> Le Thursday 17 Jan 2019 Ã 14:16:28 (-0800), Guenter Roeck a Ãcrit :
> > On Fri, Dec 21, 2018 at 11:33:56AM +0100, Vincent Guittot wrote:
> > > From: Thara Gopinath <thara.gopinath@xxxxxxxxxx>
> > >
> > > This patch replaces jiffies based accounting for runtime_active_time
> > > and runtime_suspended_time with ktime base accounting. This makes the
> > > runtime debug counters inline with genpd and other pm subsytems which
> > > uses ktime based accounting.
> > >
> > > timekeeping is initialized before pm_runtime_init() so ktime_get() will
> > > be ready before first call. In fact, timekeeping_init() is called early
> > > in start_kernel() which is way before driver_init() (and that's when
> > > devices can start to be initialized) called from rest_init() via
> > > kernel_init_freeable() and do_basic_setup().
> > This is not (always) correct. My qemu "collie" boot test fails with this
> > patch applied. Reverting the patch fixes the problem. Bisect log attached.
>
> Can you try the patch below ?
> ktime_get_mono_fast_ns() has the advantage of being init with dummy clock so
> it can be used at early_init.
Yes, that works.

Guenter

> ---
>   drivers/base/power/runtime.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index ae1c728..118c7f6 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -66,7 +66,7 @@ static int rpm_suspend(struct device *dev, int rpmflags);
>    */
>   void update_pm_runtime_accounting(struct device *dev)
>   {
> -	u64 now = ktime_to_ns(ktime_get());
> +	u64 now = ktime_get_mono_fast_ns();
>   	u64 delta;
>   
>   	delta = now - dev->power.accounting_timestamp;
> @@ -1507,7 +1507,7 @@ void pm_runtime_init(struct device *dev)
>   	dev->power.request_pending = false;
>   	dev->power.request = RPM_REQ_NONE;
>   	dev->power.deferred_resume = false;
> -	dev->power.accounting_timestamp = ktime_to_ns(ktime_get());
> +	dev->power.accounting_timestamp = ktime_get_mono_fast_ns();
>   	INIT_WORK(&dev->power.work, pm_runtime_work);
>   
>   	dev->power.timer_expires = 0;