linux-kernel - Re: [PATCH v4 0/5] Functional dependencies between devices

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Date:   Thu, 29 Sep 2016 14:27:36 +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.org>,
        Lukas Wunner <lukas@...ner.de>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Luis R. Rodriguez" <mcgrof@...e.com>
Subject: Re: [PATCH v4 0/5] Functional dependencies between devices

On Thursday, September 29, 2016 08:58:43 AM Marek Szyprowski wrote:
> Hi Rafael,
> 
> On 2016-09-29 02:24, Rafael J. Wysocki wrote:
> > Hi Everyone,
> >
> > On Thursday, September 08, 2016 11:25:44 PM 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 slightly outdated now).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.
> >> An update here.
> >>
> >> The first patch hasn't changed, so I'm resending it.
> >>
> >> The majority of changes in the other patches are in order to address Lukas'
> >> comments.
> >>
> >> First off, I added a DEVICE_LINK_STATELESS flag that will prevent the driver
> >> core from trying to maintain device links having it set.
> >>
> >> Also, the DEVICE_LINK_PERSISTENT flag was dropped (as link "persistence" is
> >> the default behavior now) and there's a new one, DEVICE_LINK_AUTOREMOVE,
> >> that will cause the driver core to remove the link on the consumer driver
> >> unbind.
> >>
> >> Moreover, the code checks attempts to create a link between a parent and a
> >> child device now and actively prevents that from happening.
> >>
> >> The changelog of the second patch has been updated as requested by Ulf.
> >>
> >> The third patch was updated to fix a bug related to the (previously missing)
> >> clearing of power.direct_complete for supplier devices having consumers that
> >> don't use direct_complete.
> >>
> >> The next two (runtime PM) patches turned out to be unnecessary, so I've
> >> dropped them.
> >>
> >> The runtime PM patch [4/5] was reorganized somewhat to reduce the
> >> indentation
> >> level in there, but the code flow introduced by it is essentially the same
> >> and the last patch was simply rebased on top of the new series.
> > Time for another update. :-)
> >
> > Fewer changes this time, mostly to address issues found by Lukas and Marek.
> >
> > The most significant one is to make device_link_add() cope with the case when
> > the consumer device has not been registered yet when it is called.  The
> > supplier device still is required to be registered and the function will return
> > NULL if that is not the case.
> >
> > Another significant change is in patch [4/5] that now makes the core apply
> > pm_runtime_get_sync()/pm_runtime_put() to supplier devices around the probing
> > of a consumer one (in analogy with the parent).
> 
> Thanks for the update! Updated version fixes all the remaining issues.
> 
> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

Thanks Marek!