[RFC/PATCH 2/2] OMAP3: CPUidle: trigger early idle notification call chain

[Sripathy, Vishwanath]

Kevin,

> -----Original Message-----
> From: linux-omap-owner at vger.kernel.org [mailto:linux-omap-
> owner at vger.kernel.org] On Behalf Of Kevin Hilman
> Sent: Thursday, October 21, 2010 5:09 AM
> To: linux-omap at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Subject: [RFC/PATCH 2/2] OMAP3: CPUidle: trigger early idle notification call chain
> 
> During the early part of the CPUidle path (state selection by the
> governer, checking for device activity, etc.) there is no (good)
> reason to have interrupts disabled.
> 
> Therefore, enable interrupts early in the CPUidle path and then
> trigger the "early" idle notifier call chain after device activity
> checks and the next power states have been programmed.  Interrupts are
> then (re)disabled after the final state is selected.
> 
> Signed-off-by: Kevin Hilman <khilman at deeprootsystems.com>
> ---
>  arch/arm/mach-omap2/cpuidle34xx.c |   27 ++++++++++++++++++++++++--
> -
>  1 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/cpuidle34xx.c b/arch/arm/mach-
> omap2/cpuidle34xx.c
> index 0d50b45..8c57360 100644
> --- a/arch/arm/mach-omap2/cpuidle34xx.c
> +++ b/arch/arm/mach-omap2/cpuidle34xx.c
> @@ -30,6 +30,7 @@
>  #include <plat/powerdomain.h>
>  #include <plat/clockdomain.h>
>  #include <plat/serial.h>
> +#include <plat/common.h>
> 
>  #include "pm.h"
>  #include "control.h"
> @@ -128,12 +129,14 @@ static int omap3_enter_idle(struct cpuidle_device *dev,
>  	/* Used to keep track of the total time in idle */
>  	getnstimeofday(&ts_preidle);
> 
> -	local_irq_disable();
> -	local_fiq_disable();
> -
>  	pwrdm_set_next_pwrst(mpu_pd, mpu_state);
>  	pwrdm_set_next_pwrst(core_pd, core_state);
> 
> +	omap_early_idle_notifier_start();
> +
> +	local_irq_disable();
> +	local_fiq_disable();
> +
>  	if (omap_irq_pending() || need_resched())
>  		goto return_sleep_time;
> 
> @@ -157,6 +160,8 @@ return_sleep_time:
>  	local_irq_enable();
>  	local_fiq_enable();
> 
> +	omap_early_idle_notifier_end();
It appears that idle notifiers (for restore path) are called after getnstimeofday is called which means time spent in idle callbacks are not accounted in cpuidle time. 
Will it not impact the cpuidle c state prediction and latency computation?

Regards
Vishwa

> +
>  	return ts_idle.tv_nsec / NSEC_PER_USEC + ts_idle.tv_sec * USEC_PER_SEC;
>  }
> 
> @@ -459,6 +464,21 @@ struct cpuidle_driver omap3_idle_driver = {
>  	.owner = 	THIS_MODULE,
>  };
> 
> +static int omap3_idle_prepare(struct cpuidle_device *dev)
> +{
> +	/*
> +	 * Enable interrupts during the early part of the CPUidle path.
> +	 * They are later (re)disabled when the final state is selected.
> +	 *
> +	 * The primary reason for this is to enable non-atomic idle
> +	 * notifications to drivers that want to coordinate device
> +	 * idle transitions with CPU idle transitions.
> +	 */
> +	local_irq_enable();
> +
> +	return 0;
> +}
> +
>  /**
>   * omap3_idle_init - Init routine for OMAP3 idle
>   *
> @@ -482,6 +502,7 @@ int __init omap3_idle_init(void)
> 
>  	dev = &per_cpu(omap3_idle_dev, smp_processor_id());
> 
> +	dev->prepare = omap3_idle_prepare;
>  	for (i = OMAP3_STATE_C1; i < OMAP3_MAX_STATES; i++) {
>  		cx = &omap3_power_states[i];
>  		state = &dev->states[count];
> --
> 1.7.2.1
> 
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