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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Thu, 10 Nov 2016 00:42:51 +0100
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Subject: Re: [PATCH v6 7/7] iommu/exynos: Use device dependency links to
 control runtime pm
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
        Linux PM <linux-pm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:AMD IOMMU (AMD-VI)" <iommu@lists.linux-foundation.org>,
        Linux Samsung SoC <linux-samsung-soc@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>, Inki Dae <inki.dae@samsung.com>,
        Kukjin Kim <kgene@kernel.org>, Krzysztof Kozlowski <krzk@kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Mark Brown <broonie@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Lukas Wunner <lukas@wunner.de>, Kevin Hilman <khilman@kernel.org>,
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        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Grant Likely <grant.likely@secretlab.ca>,
        Mauro Carvalho Chehab <mchehab@osg.samsung.com>
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On Thu, Nov 10, 2016 at 12:31 AM, Luis R. Rodriguez <mcgrof@kernel.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