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Date: Thu, 12 Feb 2015 14:26:43 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Thomas Gleixner <tglx@linutronix.de>, Alan Cox <alan@linux.intel.com>,
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        Kristen Carlson Accardi <kristen@linux.intel.com>,
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Subject: Re: [PATCH 5/6] intel_idle: Add ->enter_freeze callbacks
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On Wed, Feb 11, 2015 at 05:04:17AM +0100, Rafael J. Wysocki wrote:
> @@ -131,28 +133,32 @@ static struct cpuidle_state nehalem_csta
>  		.flags = MWAIT2flg(0x00),
>  		.exit_latency = 3,
>  		.target_residency = 6,
> -		.enter = &intel_idle },
> +		.enter = &intel_idle,
> +		.enter_freeze = intel_idle_freeze, },
>  	{
>  		.name = "C1E-NHM",
>  		.desc = "MWAIT 0x01",
>  		.flags = MWAIT2flg(0x01),
>  		.exit_latency = 10,
>  		.target_residency = 20,
> -		.enter = &intel_idle },
> +		.enter = &intel_idle,
> +		.enter_freeze = intel_idle_freeze, },
>  	{
>  		.name = "C3-NHM",
>  		.desc = "MWAIT 0x10",
>  		.flags = MWAIT2flg(0x10) | CPUIDLE_FLAG_TLB_FLUSHED,
>  		.exit_latency = 20,
>  		.target_residency = 80,
> -		.enter = &intel_idle },
> +		.enter = &intel_idle,
> +		.enter_freeze = intel_idle_freeze, },
>  	{
>  		.name = "C6-NHM",
>  		.desc = "MWAIT 0x20",
>  		.flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
>  		.exit_latency = 200,
>  		.target_residency = 800,
> -		.enter = &intel_idle },
> +		.enter = &intel_idle,
> +		.enter_freeze = intel_idle_freeze, },
>  	{
>  		.enter = NULL }
>  };

Why bother with enter_freeze() for any but the deepest state (C6 in this
case)?

Also, should we ignore things like intel_idle.max_cstate for this
selection?