linux-kernel - Re: [PATCH 1/3] cpuidle: exynos: Allow to use the driver without AFTR

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Date:	Mon, 21 Jul 2014 11:53:32 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene.kim@...sung.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Sachin Kamat <sachin.kamat@...sung.com>,
	Tushar Behera <tushar.behera@...aro.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
CC:	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>
Subject: Re: [PATCH 1/3] cpuidle: exynos: Allow to use the driver without
 AFTR

On 07/21/2014 10:36 AM, Krzysztof Kozlowski wrote:
> Allow the driver to be used when AFTR enter function is not provided
> (device platform data is NULL).
>
> This actually does not give any special energy-saving benefits but
> allows to track the idle time of each core. Additionally it is a safe
> way to validate supplied platform data.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

I think we already talk about this in the mailing list several times.
It does not make sense to enable the cpuidle driver for WFI just for the 
sake of tracking via sysfs some idle timings.

Using the cpuidle driver means using the underlying cpuidle 
infrastructure with all the stats computation in the governor.

If there is a *real* need of a WFI cpuidle driver, then a generic WFI 
cpuidle driver could be implemented to supersede this one.

It took a while to cleanup this driver and remove all the hacks around 
this AFTR state... :)



> ---
>   drivers/cpuidle/cpuidle-exynos.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/cpuidle/cpuidle-exynos.c b/drivers/cpuidle/cpuidle-exynos.c
> index 7c0151263828..5325a394be7e 100644
> --- a/drivers/cpuidle/cpuidle-exynos.c
> +++ b/drivers/cpuidle/cpuidle-exynos.c
> @@ -77,7 +77,10 @@ static int exynos_cpuidle_probe(struct platform_device *pdev)
>   {
>   	int ret;
>
> +	/* If NULL enter only WFI */
>   	exynos_enter_aftr = (void *)(pdev->dev.platform_data);
> +	if (!exynos_enter_aftr)
> +		exynos_idle_driver.state_count = 1;
>
>   	ret = cpuidle_register(&exynos_idle_driver, NULL);
>   	if (ret) {
>


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