linux-kernel - Re: [PATCH v4 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT

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Date:   Tue, 29 Nov 2022 17:17:49 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Anup Patel <anup@...infault.org>
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Jones <ajones@...tanamicro.com>,
        Atish Patra <atishp@...shpatra.org>,
        Samuel Holland <samuel@...lland.org>,
        devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] clocksource: timer-riscv: Set
 CLOCK_EVT_FEAT_C3STOP based on DT

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@...rochip.com> 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@...tanamicro.com>
> >
> > I thought I had left an R-b on this one?
> > Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> >
> > 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 :)

Thanks again for helping sort this mess out, I see it helped with your
IPI series too!

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
> > >