linux-kernel - Re: [RFC 2/8] ARM: twd: register clock event for 1 core SMP

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Date:	Mon, 18 Feb 2013 07:47:29 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Afzal Mohammed <afzal@...com>
CC:	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Nicolas Pitre <nico@...aro.org>, Sekhar Nori <nsekhar@...com>,
	Will Deacon <will.deacon@....com>,
	Rob Herring <rob.herring@...xeda.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Syed Mohammed Khasim <khasim@...com>
Subject: Re: [RFC 2/8] ARM: twd: register clock event for 1 core SMP

On 02/18/2013 12:30 AM, Afzal Mohammed wrote:
> Register percpu local timer for scheduler tick in the case of one core
> SMP configuration. In other cases - secondary cpu's as well as boot
> cpu's having more than one core, this is being registered as per
> existing boot flow, with a difference that they happens after delay
> calibration. Registering the clock for tick in case of one core should
> be done before Kernel calibrates delay (this is required to boot,
> unless local timer is the only one registered for tick). Registering
> twd local timer at init_time (which platforms are doing now) helps
> achieve that with the proposed change.
> 
> This helps in an almost booting Kernel (minimal) by only relying on
> ARM parts for an A9 one core SMP.
> 
> Signed-off-by: Afzal Mohammed <afzal@...com>
> ---
>  arch/arm/kernel/smp_twd.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
> index 616268c..118f4f2 100644
> --- a/arch/arm/kernel/smp_twd.c
> +++ b/arch/arm/kernel/smp_twd.c
> @@ -335,6 +335,9 @@ static int __init twd_local_timer_common_register(struct device_node *np)
>  
>  	twd_get_clock(np);
>  
> +	if (num_possible_cpus() == 1)
> +		twd_timer_setup(evt);
> +

Shouldn't this be fixed in the core code, so the same issue is fixed for
all timers?

Rob

>  	return 0;
>  
>  out_irq:
> 

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