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

[Conor Dooley]

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.

Thanks,
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
>