linux-kernel - Re: [PATCH v11 0/4] iommu/arm-smmu: Add runtime pm/sleep support

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Date:   Mon, 09 Apr 2018 04:22:09 +0000
From:   Tomasz Figa <tfiga@...omium.org>
To:     Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>
Cc:     "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rob Clark <robdclark@...il.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        Lukas Wunner <lukas@...ner.de>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>
Subject: Re: [PATCH v11 0/4] iommu/arm-smmu: Add runtime pm/sleep support

Hi Will, Robin,

On Thu, Mar 22, 2018 at 7:22 PM Vivek Gautam <vivek.gautam@...eaurora.org>
wrote:

> This series provides the support for turning on the arm-smmu's
> clocks/power domains using runtime pm. This is done using the
> recently introduced device links patches, which lets the smmu's
> runtime to follow the master's runtime pm, so the smmu remains
> powered only when the masters use it.
> As not all implementations support clock/power gating, we are checking
> for a valid 'smmu->dev's pm_domain' to conditionally enable the runtime
> power management for such smmu implementations that can support it.

> This series also adds support for Qcom's arm-smmu-v2 variant that
> has different clocks and power requirements.

> Took some reference from the exynos runtime patches [1].

> With conditional runtime pm now, we avoid touching dev->power.lock
> in fastpaths for smmu implementations that don't need to do anything
> useful with pm_runtime.
> This lets us to use the much-argued pm_runtime_get_sync/put_sync()
> calls in map/unmap callbacks so that the clients do not have to
> worry about handling any of the arm-smmu's power.

> Previous version of this patch series is @ [5].

> [v11]
>     * Some more cleanups for device link. We don't need an explicit
>       delete for device link from the driver, but just set the flag
>       DL_FLAG_AUTOREMOVE.
>       device_link_add() API description says -
>       "If the DL_FLAG_AUTOREMOVE is set, the link will be removed
>       automatically when the consumer device driver unbinds."
>     * Addressed the comments for 'smmu' in arm_smmu_map/unmap().
>     * Dropped the patch [10] that introduced device_link_del_dev() API.

As far as I can see, this version addresses all the earlier comments. Do
you think this is something that you could apply?

Best regards,
Tomasz