linux-kernel - Re: [PATCH V4 6/9] cpuidle/ppc: Add basic infrastructure to enable the broadcast framework on ppc

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Date:	Fri, 29 Nov 2013 12:58:48 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
cc:	fweisbec@...il.com, paul.gortmaker@...driver.com, paulus@...ba.org,
	shangw@...ux.vnet.ibm.com, rjw@...k.pl, galak@...nel.crashing.org,
	benh@...nel.crashing.org, paulmck@...ux.vnet.ibm.com,
	arnd@...db.de, linux-pm@...r.kernel.org, rostedt@...dmis.org,
	michael@...erman.id.au, john.stultz@...aro.org,
	chenhui.zhao@...escale.com, deepthi@...ux.vnet.ibm.com,
	r58472@...escale.com, geoff@...radead.org,
	linux-kernel@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com,
	schwidefsky@...ibm.com, svaidy@...ux.vnet.ibm.com,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH V4 6/9] cpuidle/ppc: Add basic infrastructure to enable
 the broadcast framework on ppc

On Fri, 29 Nov 2013, Preeti U Murthy wrote:
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index b44b52c..cafa788 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -129,6 +129,8 @@ config PPC
>  	select GENERIC_CMOS_UPDATE
>  	select GENERIC_TIME_VSYSCALL_OLD
>  	select GENERIC_CLOCKEVENTS
> +	select GENERIC_CLOCKEVENTS_BROADCAST
> +	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST

What's the point of this config switch? It's nowhere used.

> +static int broadcast_set_next_event(unsigned long evt,
> +					struct clock_event_device *dev)
> +{
> +	return 0;
> +}
> +
> +static void broadcast_set_mode(enum clock_event_mode mode,
> +				 struct clock_event_device *dev)
> +{
> +	if (mode != CLOCK_EVT_MODE_ONESHOT)
> +		broadcast_set_next_event(DECREMENTER_MAX, dev);

What's the point of calling an empty function?  

> +}
> +
>  static void decrementer_set_mode(enum clock_event_mode mode,
>  				 struct clock_event_device *dev)
>  {
> @@ -840,6 +869,19 @@ static void register_decrementer_clockevent(int cpu)
>  	clockevents_register_device(dec);
>  }
>  
> +static void register_broadcast_clockevent(int cpu)
> +{
> +	struct clock_event_device *bc_evt = &bc_timer;
> +
> +	*bc_evt = broadcast_clockevent;
> +	bc_evt->cpumask = cpu_possible_mask;
> +
> +	printk_once(KERN_DEBUG "clockevent: %s mult[%x] shift[%d] cpu[%d]\n",
> +		    bc_evt->name, bc_evt->mult, bc_evt->shift, cpu);
> +
> +	clockevents_register_device(bc_evt);
> +}
> +
>  static void __init init_decrementer_clockevent(void)
>  {
>  	int cpu = smp_processor_id();
> @@ -854,6 +896,19 @@ static void __init init_decrementer_clockevent(void)
>  	register_decrementer_clockevent(cpu);
>  }
>  
> +static void __init init_broadcast_clockevent(void)
> +{
> +	int cpu = smp_processor_id();
> +
> +	clockevents_calc_mult_shift(&broadcast_clockevent, ppc_tb_freq, 4);
> +
> +	broadcast_clockevent.max_delta_ns =
> +		clockevent_delta2ns(DECREMENTER_MAX, &broadcast_clockevent);
> +	broadcast_clockevent.min_delta_ns =
> +		clockevent_delta2ns(2, &broadcast_clockevent);

clockevents_config()

Thanks,

	tglx
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