linux-kernel - Re: [PATCH 4/6] arm: mach-omap2: remove "OMAP_DEVICE_NO_IDLE_ON

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Date:	Fri, 19 Apr 2013 07:52:23 -0700
From:	Kevin Hilman <khilman@...aro.org>
To:	Sourav Poddar <sourav.poddar@...com>
Cc:	<gregkh@...uxfoundation.org>, <tony@...mide.com>,
	<rmk+kernel@....linux.org.uk>, <linux-serial@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] arm: mach-omap2: remove "OMAP_DEVICE_NO_IDLE_ON_SUSPEND" check

Sourav Poddar <sourav.poddar@...com> writes:

[...]

> Yes, got your point. omap_device_idle should not be called only
> for console uart.
>
> Just did a quick testing by including the following hunk on top of my
> patch series..
>
> diff --git a/arch/arm/mach-omap2/omap_device.c
> b/arch/arm/mach-omap2/omap_device.c
> index c226946..7480e87 100644
> --- a/arch/arm/mach-omap2/omap_device.c
> +++ b/arch/arm/mach-omap2/omap_device.c
> @@ -617,8 +617,10 @@ static int _od_suspend_noirq(struct device *dev)
>         ret = pm_generic_suspend_noirq(dev);
>
>         if (!ret && !pm_runtime_status_suspended(dev)) {
> -               if (pm_generic_runtime_suspend(dev) == 0)
> +               if (pm_generic_runtime_suspend(dev) == 0) {
> +                       omap_device_idle(pdev);
>                         od->flags |= OMAP_DEVICE_SUSPENDED;
> +               }
>         }
>
>         return ret;
> @@ -631,6 +633,7 @@ static int _od_resume_noirq(struct device *dev)
>
>         if ((od->flags & OMAP_DEVICE_SUSPENDED) &&
>             !pm_runtime_status_suspended(dev)) {
> +               omap_device_enable(pdev);
>                 od->flags &= ~OMAP_DEVICE_SUSPENDED;
>                 pm_generic_runtime_resume(dev);
>         }
> And found the wakeup from UART is no more functional.
> So, the omap_device_idle gets called for console UART also, thereby
> preventing the "no_idle_on_suspend" theory.
>
> Hence, merely putting prepare/complete callback the way I did is not
> helping.
> We need to delete omap_device_idle also, which I agree is not correct.
> So, we need a way to bypass this "omap_device_idle"
> call for console UART. ?

OK, I see what's happening now.

How about this: rather than using prepare/complete callbacks, can you
use the runtime_suspend callback to return an error code during suspend?
(only for the console, and only when no_console_suspend is enabled, and
only during suspend)

Since _od_suspend_noirq checks to be sure the drivers ->runtime_suspend
callback succeeds before it calls omap_device_idle(), if you report a
failure, omap_device_idle will not be called.

Kevin


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