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

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Date:	Wed, 10 Aug 2011 17:55:41 +0530
From:	"Pedanekar, Hemant" <hemantp@...com>
To:	Tony Lindgren <tony@...mide.com>
CC:	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] omap: timer: Set dmtimer used as clocksource in
 autoreload mode

Tony Lindgren wrote on Wednesday, August 10, 2011 5:21 PM:

> * 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

Yes, that would be better - I didn't think about loadable module option.

Thanks.
   Hemant--
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