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

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Date: Thu, 25 Jan 2024 17:04:03 +0000
From: Leyfoon Tan <leyfoon.tan@...rfivetech.com>
To: Anup Patel <apatel@...tanamicro.com>
CC: Daniel Lezcano <daniel.lezcano@...aro.org>, Thomas Gleixner
	<tglx@...utronix.de>, Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley
	<paul.walmsley@...ive.com>, Albert Ou <aou@...s.berkeley.edu>,
	"atishp@...osinc.com" <atishp@...osinc.com>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Ley Foon Tan
	<lftan.linux@...il.com>
Subject: RE: [PATCH] clocksource: timer-riscv: Clear timer interrupt on timer
 initialization



> -----Original Message-----
> From: Anup Patel <apatel@...tanamicro.com>
> Sent: Friday, January 26, 2024 1:00 AM
> To: Leyfoon Tan <leyfoon.tan@...rfivetech.com>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>; Thomas Gleixner
> <tglx@...utronix.de>; Palmer Dabbelt <palmer@...belt.com>; Paul Walmsley
> <paul.walmsley@...ive.com>; Albert Ou <aou@...s.berkeley.edu>;
> atishp@...osinc.com; linux-riscv@...ts.infradead.org; linux-
> kernel@...r.kernel.org; Ley Foon Tan <lftan.linux@...il.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@...rfivetech.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@...rfivetech.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