linux-kernel - Re: [PATCH v3 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT

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Date:   Fri, 25 Nov 2022 13:13:04 +0000
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Anup Patel <apatel@...tanamicro.com>
CC:     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>,
        Anup Patel <anup@...infault.org>, <devicetree@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] clocksource: timer-riscv: Set
 CLOCK_EVT_FEAT_C3STOP based on DT

On Fri, Nov 25, 2022 at 04:51:05PM +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.

I need to go do some testing on what setting the C3STOP flag does on
platforms other than PolarFire SoC. I'm not sure that we should be
enabling this flag *at all* until we know that it does not break on
other platforms too.

Hopefully I'll get to it tonight or tomorrow..

> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> ---
>  drivers/clocksource/timer-riscv.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index a0d66fabf073..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)
> @@ -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
>