linux-kernel - Re: [Update][PATCH 6/10] PM / Domains: System-wide transitions support for generic domains (v5)

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Date:	Sat, 9 Jul 2011 16:15:38 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Kevin Hilman <khilman@...com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Magnus Damm <magnus.damm@...il.com>,
	Paul Walmsley <paul@...an.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-sh@...r.kernel.org,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [Update][PATCH 6/10] PM / Domains: System-wide transitions support for generic domains (v5)

On Friday, July 08, 2011, Rafael J. Wysocki wrote:
...
> 
> Well, in fact, since we already have .active_wakeup(), what about the
> following patch (on top of https://lkml.org/lkml/2011/7/8/223):

Well, it is wrong, because we've been discussing devices that are _not_
enabled to wake up the system.

> ---
>  drivers/base/power/domain.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> Index: linux-2.6/drivers/base/power/domain.c
> ===================================================================
> --- linux-2.6.orig/drivers/base/power/domain.c
> +++ linux-2.6/drivers/base/power/domain.c
> @@ -519,6 +519,10 @@ static int pm_genpd_prepare(struct devic
>  		return -EBUSY;
>  	}
>  
> +	if (device_may_wakeup(dev)

So, this should have been !device_may_wakeup(dev), _but_ ...

> +	    && !(genpd->active_wakeup && genpd->active_wakeup(dev)))
> +		pm_runtime_resume(dev);
> +
>  	genpd_acquire_lock(genpd);
>  
>  	if (genpd->prepared_count++ == 0)

There's one more case to consider, namely devices that are runtime
suspended, set up to wake up the system from sleep states (ie. device_may_wakeup(dev)
returns "true") and such that genpd->active_wakeup(dev) returns "true" for them,
because they need to be resumed at this point too (arguably, it makes a little
sense to runtime suspend such devices, but that's possible in principle).

So, IMO, the patch should look like this:

---
 drivers/base/power/domain.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

Index: linux-2.6/drivers/base/power/domain.c
===================================================================
--- linux-2.6.orig/drivers/base/power/domain.c
+++ linux-2.6/drivers/base/power/domain.c
@@ -486,6 +486,22 @@ static void pm_genpd_sync_poweroff(struc
 }
 
 /**
+ * resume_needed - Check whether to resume a device before system suspend.
+ * @dev: Device to handle.
+ * @genpd: PM domain the device belongs to.
+ */
+static bool resume_needed(struct device *dev, struct generic_pm_domain *genpd)
+{
+	bool active_wakeup;
+
+	if (!device_can_wakeup(dev))
+		return false;
+
+	active_wakeup = genpd->active_wakeup && genpd->active_wakeup(dev);
+	return device_may_wakeup(dev) ? active_wakeup : !active_wakeup;
+}
+
+/**
  * pm_genpd_prepare - Start power transition of a device in a PM domain.
  * @dev: Device to start the transition of.
  *
@@ -519,6 +535,9 @@ static int pm_genpd_prepare(struct devic
 		return -EBUSY;
 	}
 
+	if (resume_needed(dev, genpd))
+		pm_runtime_resume(dev);
+
 	genpd_acquire_lock(genpd);
 
 	if (genpd->prepared_count++ == 0)
--
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