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

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Date:   Thu, 29 Sep 2016 08:58:43 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM list <linux-pm@...r.kernel.org>
Cc:     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

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 slightly outdated now).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>

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland