Re: [PATCH 1/3] time/sched_clock: Export sched_clock_register()

[Matthias Brugger]

On 08/02/2023 20:45, Krzysztof Kozlowski wrote:
> On 08/02/2023 20:41, Matthias Brugger wrote:
> > On 08/02/2023 15:24, Krzysztof Kozlowski wrote:
> > > On 08/02/2023 10:48, walter.chang@xxxxxxxxxxxx wrote:
> > > > From: Chun-Hung Wu <chun-hung.wu@xxxxxxxxxxxx>
> > > >
> > > > clocksource driver may use sched_clock_register()
> > > > to resigter itself as a sched_clock source.
> > > > Export it to support building such driver
> > > > as module, like timer-mediatek.c
> > > >
> > > > Signed-off-by: Chun-Hung Wu <chun-hung.wu@xxxxxxxxxxxx>
> > > > ---
> > > >    kernel/time/sched_clock.c | 4 ++--
> > > >    1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
> > > > index 8464c5acc913..8e49e87d1221 100644
> > > > --- a/kernel/time/sched_clock.c
> > > > +++ b/kernel/time/sched_clock.c
> > > > @@ -150,8 +150,7 @@ static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt)
> > > >    	return HRTIMER_RESTART;
> > > >    }
> > > >    
> > > > -void __init
> > > > -sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
> > > > +void sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
> > >
> > > Is there a non-init caller?
> > >
> > > >    {
> > > >    	u64 res, wrap, new_mask, new_epoch, cyc, ns;
> > > >    	u32 new_mult, new_shift;
> > > > @@ -223,6 +222,7 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
> > > >    
> > > >    	pr_debug("Registered %pS as sched_clock source\n", read);
> > > >    }
> > > > +EXPORT_SYMBOL_GPL(sched_clock_register);
> > >
> > > Where is the module using it?
> > >
> > > You need to bring users of these two changes, not just prepare something
> > > for your out of tree patches.
> >
> > I'd propose to add at least one driver that will need these changes, to make it
> > clear why you need that.
>
> ... and actually test if the system works fine when booted from such
> clocksource as a module. I have doubts that and unfortunately folks
> working on GKI like to put whatever stuff from mainline into modules
> even if it does not make sense for us (see long time ago discussion
> about pinctrl drivers).

Yes thinking about it twice, it makes only sense if  the Arm architecture timer 
is running. Otherwise the system will hang on boot. I know that older MediaTek 
devices had problems with that...