linux-kernel - Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT

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Date:   Fri, 2 Dec 2022 12:03:05 +0530
From:   Anup Patel <apatel@...tanamicro.com>
To:     Rob Herring <robh@...nel.org>
Cc:     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>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Anup Patel <anup@...infault.org>, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Palmer Dabbelt <palmer@...osinc.com>
Subject: Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP
 based on DT

On Fri, Dec 2, 2022 at 5:36 AM Rob Herring <robh@...nel.org> wrote:
>
> On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
> > We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> > when riscv,timer-cannot-wake-cpu 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>
> > Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> > Acked-by: Palmer Dabbelt <palmer@...osinc.com>
> > ---
> >  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..1b4b36df5484 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_cannot_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,
>
> A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break
> with this change because its existing DT will not have the new property.
>
> It needs to be the other way around which would effectively be the
> existing 'always-on' property.

There are no RISC-V platforms using C3STOP. The patch which
added C3STOP has been reverted.
(Refer, https://lore.kernel.org/lkml/a218ebf8-0fba-168d-6598-c970bbff5faf@sholland.org/T/)

I just need to rebase this patch upon the C3STOP revert patch.

>
> >       .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_cannot_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_cannot_wake_cpu = of_property_read_bool(child,
> > +                                     "riscv,timer-cannot-wake-cpu");
> > +             of_node_put(child);
> > +     }
> > +
> >       domain = NULL;
> >       child = of_get_compatible_child(n, "riscv,cpu-intc");
> >       if (!child) {
> > --
> > 2.34.1
> >
> >

Regards,
Anup