linux-kernel - Re: [RFC][PATCH] PM / Platform: Remove __weak definitions of runtime PM callbacks

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Message-Id: <201104070729.45484.rjw@sisk.pl>
Date:	Thu, 7 Apr 2011 07:29:45 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Kevin Hilman <khilman@...com>
Cc:	Magnus Damm <magnus.damm@...il.com>,
	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul Mundt <lethal@...ux-sh.org>, linux-sh@...r.kernel.org,
	grant.likely@...retlab.ca
Subject: Re: [RFC][PATCH] PM / Platform: Remove __weak definitions of runtime PM callbacks

On Thursday, April 07, 2011, Kevin Hilman wrote:
> Hi Rafael, Magnus,
> 
> "Rafael J. Wysocki" <rjw@...k.pl> writes:
> 
> > From: Rafael J. Wysocki <rjw@...k.pl>
> >
> > Remove the __weak definitions of platform bus type runtime PM
> > callbacks, make platform_dev_pm_ops point to the generic routines
> > as appropriate and allow architectures using platform_dev_pm_ops to
> > replace the runtime PM callbacks in that structure with their own
> > set.
> >
> > Convert architectures providing its own definitions of the platform
> > runtime PM callbacks to use the new mechanism.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> 
> I dont't think we should be adding yet another new interface for setting
> platform-specific runtime PM ops.
> 
> We now have 3.  Two existing ones:
> 
> 1) new device power domains (presumably preferred)
> 2) platform_bus_set_pm_ops() (disliked by many)

Hmm, I wasn't aware of that one, will have a look.

> and now the new one you create here
> 
> 3) platform_set_runtime_pm_ops()
> 
> This new one is basically the same as platform_bus_set_pm_ops(), but
> targetted only at runtime PM ops, and also has all the same problems
> that have been discussed before.  Namely, it overrides the pm ops for
> *every* device on the platform_bus, instead of targetting only specific
> devices.

This is not a problem for this particular use case.  We really want to
replace the PM ops for all of the platform devices on that platform.

Though I agree it probably makes more sense to use the existing
platform_bus_set_pm_ops() for this purpose.

> With the new device power domains, we can target specific devices.
> 
> Wouldn't the right way to go here be to convert mach-shmobile over to
> using device power domains?

Not for this particular purpose.
 
> The patch below against v2.6.39-rc2 combined with your patch (minus the
> mach-shmobile/* changes) should do it.

Unfortunately it would conflict with work in progress introducing _real_
power domains on shmobile.

Thanks,
Rafael
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