linux-kernel - Re: [PATCH v10 1/5] PM / Runtime: Allow accessing irq_safe if no PM

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Date:	Thu, 06 Nov 2014 23:51:06 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Russell King <linux@....linux.org.uk>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
	Michal Simek <michal.simek@...inx.com>,
	Kevin Hilman <khilman@...nel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v10 1/5] PM / Runtime: Allow accessing irq_safe if no PM_RUNTIME

On Thursday, November 06, 2014 09:36:46 AM Krzysztof Kozlowski wrote:
> Some drivers (e.g. bus drivers) may want to check if power.irq_safe was
> called by child driver, regardless of CONFIG_PM_RUNTIME.
> 
> An example scenario is amba/bus.c and dma/pl330.c drivers. The runtime
> suspend/resume callbacks in amba bus driver act differently if irq_safe
> was set by child driver (in irq_safe mode bus clock is only disabled).
> 
> The pl330 driver sets irq_safe and assumes that amba bus driver will
> only disable the clock in runtime PM. So in system sleep suspend
> callback the pl330 driver unprepares the clock after calling
> pm_runtime_force_suspend().
> 
> However inconsistency would appear if CONFIG_PM_RUNTIME is not set and
> child drivers do not want the irq_safe runtime PM. In such case amba bus
> driver still has to know whether child driver wanted irq_safe - by
> looking at dev->power.irq_safe field.
> 
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> ---
>  include/linux/pm.h         | 2 +-
>  include/linux/pm_runtime.h | 5 ++++-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 383fd68aaee1..b05fa954f50d 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -566,6 +566,7 @@ struct dev_pm_info {
>  	bool			ignore_children:1;
>  	bool			early_init:1;	/* Owned by the PM core */
>  	bool			direct_complete:1;	/* Owned by the PM core */
> +	unsigned int		irq_safe:1;	/* PM runtime */
>  	spinlock_t		lock;
>  #ifdef CONFIG_PM_SLEEP
>  	struct list_head	entry;
> @@ -590,7 +591,6 @@ struct dev_pm_info {
>  	unsigned int		run_wake:1;
>  	unsigned int		runtime_auto:1;
>  	unsigned int		no_callbacks:1;
> -	unsigned int		irq_safe:1;
>  	unsigned int		use_autosuspend:1;
>  	unsigned int		timer_autosuspends:1;
>  	unsigned int		memalloc_noio:1;

Well, that is a good reason to introduce a wrapper around power.irq_safe in my
view.

And define the wrapper so that it always returns false for CONFIG_PM_RUNTIME
unset.

This way not only you wouldn't need to move the flag from under the #ifdef,
but also you would make the compiler skip the relevant pieces of code
entiretly for CONFIG_PM_RUNTIME unset.

> diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
> index 367f49b9a1c9..d94a65662a60 100644
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -166,7 +166,10 @@ static inline bool pm_runtime_suspended_if_enabled(struct device *dev) { return
>  static inline bool pm_runtime_enabled(struct device *dev) { return false; }
>  
>  static inline void pm_runtime_no_callbacks(struct device *dev) {}
> -static inline void pm_runtime_irq_safe(struct device *dev) {}
> +static inline void pm_runtime_irq_safe(struct device *dev)
> +{
> +	dev->power.irq_safe = 1;
> +}
>  
>  static inline bool pm_runtime_callbacks_present(struct device *dev) { return false; }
>  static inline void pm_runtime_mark_last_busy(struct device *dev) {}
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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