linux-kernel - Re: [PATCH] MIPS: kernel: only use i8253 clocksource with periodic clockevent

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Message-ID: <20190717090322.GA8585@alpha.franken.de>
Date:   Wed, 17 Jul 2019 11:03:22 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: kernel: only use i8253 clocksource with periodic
 clockevent

On Mon, May 13, 2019 at 01:47:25PM +0200, Thomas Bogendoerfer wrote:
> i8253 clocksource needs a free running timer. This could only
> be used, if i8253 clockevent is set up as periodic.
> 
> Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@...e.de>
> ---
>  arch/mips/kernel/i8253.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/mips/kernel/i8253.c b/arch/mips/kernel/i8253.c
> index 5f209f111e59..df7ddd246eaa 100644
> --- a/arch/mips/kernel/i8253.c
> +++ b/arch/mips/kernel/i8253.c
> @@ -32,7 +32,8 @@ void __init setup_pit_timer(void)
>  
>  static int __init init_pit_clocksource(void)
>  {
> -	if (num_possible_cpus() > 1) /* PIT does not scale! */
> +	if (num_possible_cpus() > 1 || /* PIT does not scale! */
> +	    !clockevent_state_periodic(&i8253_clockevent))
>  		return 0;
>  
>  	return clocksource_i8253_init();
> -- 
> 2.13.7

Paul,

can you take it into 5.3 ? This fixes a boot ang on mips/jazz and
is the same as x86 does for quite some time.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]