[PATCH] clocksource: timer-riscv: Clear timer interrupt on timer initialization

[PATCH] clocksource: timer-riscv: Clear timer interrupt on timer initialization

[Ley Foon Tan]

In the RISC-V specification, the stimecmp register doesn't have a default
value. To prevent the timer interrupt from being triggered during timer
initialization, clear the timer interrupt by writing stimecmp with a
maximum value.

Signed-off-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
---
 drivers/clocksource/timer-riscv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index e66dcbd66566..a75a74647344 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -172,6 +172,9 @@ static int __init riscv_timer_init_common(void)
 
 	sched_clock_register(riscv_sched_clock, 64, riscv_timebase);
 
+	/* Clear timer interrupt */
+	riscv_clock_event_stop();
+
 	error = request_percpu_irq(riscv_clock_event_irq,
 				    riscv_timer_interrupt,
 				    "riscv-timer", &riscv_clock_event);
-- 
2.43.0

Re: [PATCH] clocksource: timer-riscv: Clear timer interrupt on timer initialization

[Anup Patel]

On Thu, Jan 25, 2024 at 10:25 PM Ley Foon Tan
<leyfoon.tan@starfivetech.com> wrote:
>
> In the RISC-V specification, the stimecmp register doesn't have a default
> value. To prevent the timer interrupt from being triggered during timer
> initialization, clear the timer interrupt by writing stimecmp with a
> maximum value.
>
> Signed-off-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
> ---
>  drivers/clocksource/timer-riscv.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index e66dcbd66566..a75a74647344 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -172,6 +172,9 @@ static int __init riscv_timer_init_common(void)
>
>         sched_clock_register(riscv_sched_clock, 64, riscv_timebase);
>
> +       /* Clear timer interrupt */
> +       riscv_clock_event_stop();
> +

The riscv_timer_init_common() is called only on boot HART.

I suggest doing riscv_clock_event_stop() in riscv_timer_starting_cpu()
just before enable_percpu_irq().

I also suggest adding an appropriate Fixes tag in the commit description.

Regards,
Anup

>         error = request_percpu_irq(riscv_clock_event_irq,
>                                     riscv_timer_interrupt,
>                                     "riscv-timer", &riscv_clock_event);
> --
> 2.43.0
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

RE: [PATCH] clocksource: timer-riscv: Clear timer interrupt on timer initialization

[Leyfoon Tan]

> -----Original Message-----
> From: Anup Patel <apatel@ventanamicro.com>
> Sent: Friday, January 26, 2024 1:00 AM
> To: Leyfoon Tan <leyfoon.tan@starfivetech.com>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>; Thomas Gleixner
> <tglx@linutronix.de>; Palmer Dabbelt <palmer@dabbelt.com>; Paul Walmsley
> <paul.walmsley@sifive.com>; Albert Ou <aou@eecs.berkeley.edu>;
> atishp@rivosinc.com; linux-riscv@lists.infradead.org; linux-
> kernel@vger.kernel.org; Ley Foon Tan <lftan.linux@gmail.com>
> Subject: Re: [PATCH] clocksource: timer-riscv: Clear timer interrupt on timer
> initialization
> 
> On Thu, Jan 25, 2024 at 10:25 PM Ley Foon Tan
> <leyfoon.tan@starfivetech.com> wrote:
> >
> > In the RISC-V specification, the stimecmp register doesn't have a
> > default value. To prevent the timer interrupt from being triggered
> > during timer initialization, clear the timer interrupt by writing
> > stimecmp with a maximum value.
> >
> > Signed-off-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
> > ---
> >  drivers/clocksource/timer-riscv.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/clocksource/timer-riscv.c
> > b/drivers/clocksource/timer-riscv.c
> > index e66dcbd66566..a75a74647344 100644
> > --- a/drivers/clocksource/timer-riscv.c
> > +++ b/drivers/clocksource/timer-riscv.c
> > @@ -172,6 +172,9 @@ static int __init riscv_timer_init_common(void)
> >
> >         sched_clock_register(riscv_sched_clock, 64, riscv_timebase);
> >
> > +       /* Clear timer interrupt */
> > +       riscv_clock_event_stop();
> > +
> 
> The riscv_timer_init_common() is called only on boot HART.
> 
> I suggest doing riscv_clock_event_stop() in riscv_timer_starting_cpu() just
> before enable_percpu_irq().
> 
> I also suggest adding an appropriate Fixes tag in the commit description.
> 
> Regards,
> Anup
> 

Okay, will change it.

Thanks.

Regards
Ley Foon