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

[Zhang Rui]

On Wed, 2009-08-19 at 07:58 +0800, Rafael J. Wysocki wrote:
> 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 ïdrivers/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;
> +	}

to use this, we must make sure that ïdevice_enable_async_suspend is
called before any of its child device being registered, right?
should we check this in ïïdevice_enable_async_suspend?
or at least we should add the comments stating this issue.

thanks,
rui

>  	device_pm_list_add(dev);
>  }
>  

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