linux-kernel - Re: [PATCH v6 7/7] iommu/exynos: Use device dependency links to control runtime pm

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Date:   Thu, 10 Nov 2016 00:42:51 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
        Linux Samsung SoC <linux-samsung-soc@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Inki Dae <inki.dae@...sung.com>, Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Lukas Wunner <lukas@...ner.de>,
        Kevin Hilman <khilman@...nel.org>,
        Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Grant Likely <grant.likely@...retlab.ca>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>
Subject: Re: [PATCH v6 7/7] iommu/exynos: Use device dependency links to
 control runtime pm

On Thu, Nov 10, 2016 at 12:31 AM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
> On Tue, Nov 08, 2016 at 02:29:24PM +0100, Marek Szyprowski wrote:
>> This patch uses recently introduced device dependency links to track the
>> runtime pm state of the master's device. The goal is to let SYSMMU
>> controller device's runtime PM to follow the runtime PM state of the
>> respective master's device. This way each SYSMMU controller is active
>> only when its master's device is active and can properly restore or save
>> its state instead on runtime PM transition of master's device.
>> This approach replaces old behavior, when SYSMMU controller was set to
>> runtime active once after attaching to the master device. In the new
>> approach SYSMMU controllers no longer prevents respective power domains
>> to be turned off when master's device is not being used.
>>
>> The dependency links also enforces proper order of suspending/restoring
>> devices during system sleep transition, so there is no more need to use
>> LATE_SYSTEM_SLEEP_PM_OPS-based workaround for ensuring that SYSMMUs are
>> suspended after their master devices.
>
> Patches 1-6 seems reasonable to me, however in so far as this patch is
> concerned I'd appreaciate if you and Rafael can reply to Lukas Wunner's
> questions.

Which questions exactly do you mean?

Thanks,
Rafael