Re: [PATCH v4 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Palmer Dabbelt]

On Tue, 29 Nov 2022 09:22:22 PST (-0800), apatel@xxxxxxxxxxxxxxxx wrote:
> On Tue, Nov 29, 2022 at 10:47 PM Conor Dooley <conor@xxxxxxxxxx> wrote:
> > On Tue, Nov 29, 2022 at 10:41:09PM +0530, Anup Patel wrote:
> > > On Tue, Nov 29, 2022 at 8:06 PM Conor Dooley <conor.dooley@xxxxxxxxxxxxx> wrote:
> > > >
> > > > On Tue, Nov 29, 2022 at 07:33:13PM +0530, Anup Patel wrote:
> > > > > We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> > > > > when riscv,timer-cant-wake-up DT property is present in the RISC-V
> > > > > timer DT node.
> > > > >
> > > > > This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
> > > > > based on RISC-V platform capabilities rather than having it set for
> > > > > all RISC-V platforms.
> > > > >
> > > > > Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> > > >
> > > > I thought I had left an R-b on this one?
> > > > Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> > > >
> > > > Also, I think that we need to backport *something* that disables C3STOP
> > > > which is why I had suggested keeping the revert in place.
> > > > Patch 1 of this series only solves the timer issues but does not restore
> > > > sleep states to their prior behaviour, right?
> > > > Either this patch or the revert needs to go to stable IMO.
> > >
> > > Since it works for you with the C3STOP set and broadcast timer enabled,
> > > we can directly go with this patch. I am fine including the revert as well.
> >
> > I don't mind which gets backported. To me, this one is preferable as it
> > is more "complete" but it is a bit on the new feature side of things,
> > no?
> >
> > Whoever applies it can decide, and I'll backport the revert if they
> > decide that this patch is not stable material :)

IIRC the clock folks took the original C3 patch, so that's probably the 
best way to take these as well?

> > Thanks again for helping sort this mess out, I see it helped with your
> > IPI series too!
>
> Yes, I was surprised to see that it helped the IPI series as well.
> Thanks for your patch.
>
> Regards,
> Anup
>
> > Conor.
> >
> > > > > ---
> > > > >  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
> > > > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> > > > > index 969a552da8d2..0c8bdd168a45 100644
> > > > > --- a/drivers/clocksource/timer-riscv.c
> > > > > +++ b/drivers/clocksource/timer-riscv.c
> > > > > @@ -28,6 +28,7 @@
> > > > >  #include <asm/timex.h>
> > > > >
> > > > >  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
> > > > > +static bool riscv_timer_cant_wake_cpu;
> > > > >
> > > > >  static int riscv_clock_next_event(unsigned long delta,
> > > > >               struct clock_event_device *ce)
> > > > > @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
> > > > >  static unsigned int riscv_clock_event_irq;
> > > > >  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
> > > > >       .name                   = "riscv_timer_clockevent",
> > > > > -     .features               = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
> > > > > +     .features               = CLOCK_EVT_FEAT_ONESHOT,
> > > > >       .rating                 = 100,
> > > > >       .set_next_event         = riscv_clock_next_event,
> > > > >  };
> > > > > @@ -85,6 +86,8 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
> > > > >
> > > > >       ce->cpumask = cpumask_of(cpu);
> > > > >       ce->irq = riscv_clock_event_irq;
> > > > > +     if (riscv_timer_cant_wake_cpu)
> > > > > +             ce->features |= CLOCK_EVT_FEAT_C3STOP;
> > > > >       clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
> > > > >
> > > > >       enable_percpu_irq(riscv_clock_event_irq,
> > > > > @@ -139,6 +142,13 @@ static int __init riscv_timer_init_dt(struct device_node *n)
> > > > >       if (cpuid != smp_processor_id())
> > > > >               return 0;
> > > > >
> > > > > +     child = of_find_compatible_node(NULL, NULL, "riscv,timer");
> > > > > +     if (child) {
> > > > > +             riscv_timer_cant_wake_cpu = of_property_read_bool(child,
> > > > > +                                             "riscv,timer-cant-wake-cpu");
> > > > > +             of_node_put(child);
> > > > > +     }
> > > > > +
> > > > >       domain = NULL;
> > > > >       child = of_get_compatible_child(n, "riscv,cpu-intc");
> > > > >       if (!child) {
> > > > > --
> > > > > 2.34.1
> > > > >