linux-kernel - Re: [RFC/RFT][PATCH v2 0/7] Functional dependencies between devices

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Date:   Wed, 14 Sep 2016 00:41:33 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Mark Brown <broonie@...nel.og>, Lukas Wunner <lukas@...ner.de>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Luis R. Rodriguez" <mcgrof@...e.com>
Subject: Re: [RFC/RFT][PATCH v2 0/7] Functional dependencies between devices

On Tuesday, September 13, 2016 11:58:56 AM Marek Szyprowski wrote:
> Hi Rafael,
> 
> 
> On 2016-09-08 23:25, Rafael J. Wysocki wrote:
> > Hi Everyone,
> >
> > This is a refresh of the functional dependencies series that I posted last
> > year and which has picked up by Marek quite recently.  For reference, appended
> > is my introductory message sent previously (which may be slightly outdated now).
> >
> > As last time, the first patch rearranges the code around __device_release_driver()
> > a bit to prepare it for the next one (it actually hasn't changed AFAICS).
> >
> > The second patch introduces the actual device links mechanics, but without
> > system suspend/resume and runtime PM support which are added by the subsequent
> > patches.
> >
> > Some bugs found by Marek during his work on these patches should be fixed
> > here.  In particular, the endless recursion in device_reorder_to_tail()
> > which simply was broken before.
> >
> > There are two additional patches to address the issue with runtime PM support
> > that occured when runtime PM was disabled for some suppliers due to a PM
> > sleep transition in progress.  Those patches simply make runtime PM helpers
> > return 0 in that case which may be controversial, so please let me know if
> > there are concerns about those.
> >
> > The way device_link_add() works is a bit different, as it takes an additional
> > status argument now.  That makes it possible to create a link in any state,
> > with extra care of course, and should address the problem pointed to by Lukas
> > during the previous discussion.
> >
> > Also some comments from Tomeu have been addressed.
> >
> > This hasn't been really tested yet and I'm sort of relying on Marek to test
> > it, because he has a use case ready.  Hence, the RFT tag on the series.
> 
> I've checked it with my updated Exynos SYSMMU patches and it works 
> really well.
> Both runtime pm and system sleep. It took some time to do the test, because
> this patchset changed somehow the probe order of the devices, what revealed
> some issues related to incorrect driver and device registration in Samsung
> Exynos FIMC-IS driver, but those were not related to Rafael's changes.
> I will post my patches in a few minutes.
> 
> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

Thanks, much appreciated!

> Rafael, BTW, didn't you plan to change the name of the device_link_add()
> function to device_dependency_add() to avoid confusion with network device
> "link"?

I was concerned about the "devlink" name in particular, but I thought that
struct device_link would be distinct enough.  If not, I can still change it.

Thanks,
Rafael