linux-kernel - Re: [PATCH v2 6/6] ARM: tegra: cpuidle: use firmware for power down

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Date:	Tue, 11 Feb 2014 17:36:50 -0800
From:	Olof Johansson <olof@...om.net>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Tomasz Figa <t.figa@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org, gnurou@...il.com
Subject: Re: [PATCH v2 6/6] ARM: tegra: cpuidle: use firmware for power down

On Fri, Feb 07, 2014 at 01:35:06PM +0900, Alexandre Courbot wrote:
> Attempt to invoke the prepare_idle() and do_idle() firmware calls
> to power down a CPU so an underlying firmware gets informed of
> the idle operation and performs it by itself if designed in such a way.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
>  arch/arm/mach-tegra/cpuidle-tegra114.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-tegra/cpuidle-tegra114.c b/arch/arm/mach-tegra/cpuidle-tegra114.c
> index e0b87300243d..558067ddc186 100644
> --- a/arch/arm/mach-tegra/cpuidle-tegra114.c
> +++ b/arch/arm/mach-tegra/cpuidle-tegra114.c
> @@ -19,6 +19,7 @@
>  #include <linux/cpuidle.h>
>  #include <linux/cpu_pm.h>
>  #include <linux/clockchips.h>
> +#include <asm/firmware.h>
>  
>  #include <asm/cpuidle.h>
>  #include <asm/suspend.h>
> @@ -45,7 +46,15 @@ static int tegra114_idle_power_down(struct cpuidle_device *dev,
>  
>  	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
>  
> -	cpu_suspend(0, tegra30_sleep_cpu_secondary_finish);
> +	call_firmware_op(prepare_idle);
> +
> +	switch (call_firmware_op(do_idle)) {
> +	case -ENOSYS:
> +		cpu_suspend(0, tegra30_sleep_cpu_secondary_finish);
> +		break;
> +	default:
> +		break;

Do you expect other cases down the road? If not, this is a simple if instead:

	/* Only call cpu_suspend if TF didn't handle the pre-suspend logic */
	if (call_firmware_op(do_idle) == -ENOSYS)
		cpu_suspend(....);


-Olof
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