linux-kernel - Re: [PATCH] omap: timer: Set dmtimer used as clocksource in autoreload mode

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Message-ID: <20110810115122.GH1939@atomide.com>
Date:	Wed, 10 Aug 2011 04:51:22 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Hemant Pedanekar <hemantp@...com>
Cc:	linux-omap@...r.kernel.org, Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] omap: timer: Set dmtimer used as clocksource in
 autoreload mode

* Hemant Pedanekar <hemantp@...com> [110809 20:46]:
> If CONFIG_OMAP_32K_TIMER is not selected and dmtimer is used as clocksource, the
> timer stops counting once overflow occurs as it was not set in autoreload mode.
> This results into timekeeping failure: for example, 'sleep 1' at the shell after
> the timer counter overflow would hang.
> 
> This patch sets up autoreload when starting the clocksource timer which fixes
> the above issue.
> 
> Signed-off-by: Hemant Pedanekar <hemantp@...com>
> ---
>  arch/arm/mach-omap2/timer.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
> index e964072..796b935 100644
> --- a/arch/arm/mach-omap2/timer.c
> +++ b/arch/arm/mach-omap2/timer.c
> @@ -293,7 +293,7 @@ static void __init omap2_gp_clocksource_init(int gptimer_id,
>  	pr_info("OMAP clocksource: GPTIMER%d at %lu Hz\n",
>  		gptimer_id, clksrc.rate);
>  
> -	__omap_dm_timer_load_start(clksrc.io_base, OMAP_TIMER_CTRL_ST, 0, 1);
> +	omap_dm_timer_set_load_start(&clksrc, 1, 0);
>  	init_sched_clock(&cd, dmtimer_update_sched_clock, 32, clksrc.rate);
>  
>  	if (clocksource_register_hz(&clocksource_gpt, clksrc.rate))

You should be able to just set the autoreload mode by changing to use
OMAP_TIMER_CTRL_POSTED | OMAP_TIMER_CTRL_AR in the __omap_dm_timer_load_start
above.

This avoids calling something that might be a loadable module eventually.

Regards,

Tony
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