linux-kernel - Re: [RFC][PATCH 0/7] PM: Asynchronous suspend and resume (updated)

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Date:	Wed, 19 Aug 2009 01:58:09 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Zhang Rui <rui.zhang@...el.com>,
	Alan Stern <stern@...land.harvard.edu>
Cc:	"linux-pm" <linux-pm@...ts.linux-foundation.org>,
	"linux-acpi" <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Greg KH <gregkh@...e.de>
Subject: Re: [RFC][PATCH 0/7] PM: Asynchronous suspend and resume (updated)

On Tuesday 18 August 2009, Rafael J. Wysocki wrote:
> On Tuesday 18 August 2009, Zhang Rui wrote:
> > On Mon, 2009-08-17 at 08:15 +0800, Rafael J. Wysocki wrote:
> > > On Wednesday 12 August 2009, Rafael J. Wysocki wrote:
> > > > Hi,
> > > > 
> > > > The following patches introduce a mechanism allowing us to execute device
> > > > drivers' suspend and resume callbacks asynchronously during system sleep
> > > > transitions, such as suspend to RAM.  The idea is explained in the [1/1] patch
> > > > message.
> > > 
> > > Changes:
> > > 
> > > * Added [1/7] that fixes kerneldoc comments in drivers/base/power/main.c
> > >   (this is a 2.6.32 candidate).
> > > 
> > > * Added [2/7] adding a framework for representing PM link (idea described
> > >   in the patch message).
> > > 
> > > * [3/7] is the async resume patch (idea described in the patch message).
> > > 
> > > * [4/7] is the async suspend patch.
> > > 
> > > * [5/7] - [7/7] set async_suspend for devices in a few selected subsystems.
> > > 
> > > The patches have been tested on HP nx6325.
> > > 
> > I tried this patch set and it does work. :)
> > But unfortunately it doesn't save too much time.
> > 
> > I still think that the child device should inherit its parent's
> > async_suspend flag to do the asynchronous resume more efficiently.
> > 
> > or at least we should provide such an interface
> > in drivers/base/power/common.c, so that device can tell the device core
> > to inherit this flag if there is no off-tree dependency.
> 
> Well, I'd prefer to identify all of the off-tree dependencies that have to be
> taken into account and handle all devices asynchronously.

Anyway, I have tested the appended patch on top of [1/7]-[7/7] and my test box
appears to work fine with it, although it doesn't work in the "async for all"
case.

I guess the next step will be to see which devices are not handled
asynchronously with the patch below and try to figure out which of them
break(s) things.

Thanks,
Rafael

---
 drivers/base/power/common.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/base/power/common.c
===================================================================
--- linux-2.6.orig/drivers/base/power/common.c
+++ linux-2.6/drivers/base/power/common.c
@@ -32,7 +32,11 @@ void device_pm_add(struct device *dev)
 	pr_debug("PM: Adding info for %s:%s\n",
 		 dev->bus ? dev->bus->name : "No Bus",
 		 kobject_name(&dev->kobj));
-	pm_link_add(dev, dev->parent);
+	if (dev->parent) {
+		pm_link_add(dev, dev->parent);
+		if (dev->parent->power.async_suspend)
+			dev->power.async_suspend = true;
+	}
 	device_pm_list_add(dev);
 }
 
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