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

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Date:   Tue, 29 Nov 2022 10:43:48 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     apatel@...tanamicro.com
CC:     Conor Dooley <conor@...nel.org>, anup@...infault.org,
        Conor Dooley <conor.dooley@...rochip.com>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        daniel.lezcano@...aro.org, tglx@...utronix.de,
        ajones@...tanamicro.com, atishp@...shpatra.org,
        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, 29 Nov 2022 09:22:22 PST (-0800), apatel@...tanamicro.com wrote:
> On Tue, Nov 29, 2022 at 10:47 PM Conor Dooley <conor@...nel.org> 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@...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 :)

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
>> > > >