linux-kernel - Re: [PATCH v8 0/5] iommu/arm-smmu: Add runtime pm/sleep support

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Date:   Mon, 5 Mar 2018 22:25:42 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
Cc:     Joerg Roedel <joro@...tes.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>,
        Rob Clark <robdclark@...il.com>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        jcrouse@...eaurora.org, Stephen Boyd <sboyd@...eaurora.org>,
        Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v8 0/5] iommu/arm-smmu: Add runtime pm/sleep support

Hi Vivek,

On Fri, Mar 2, 2018 at 7:10 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.
>
> It 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].
>
> After another round of discussion [3], we now finally seem to be
> in agreement to add a flag based on compatible, a flag that would
> indicate if a particular implementation of arm-smmu supports
> runtime pm or not.
> 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.
> The patch that exported couple of pm_runtime suppliers APIS, viz.
> pm_runtime_get_suppliers(), and pm_runtime_put_suppliers() can be
> dropped since we don't have a user now for these APIs.
> Thanks Rafael for reviewing the changes, but looks like we don't
> need to export those APIs for some more time. :)
>
> Previous version of this patch series is @ [5].

Thanks for addressing my comments. There is still a bit of space for
improving the granularity of power management, as far as I understood
how it works on SDM845 correctly, but as a first step, this should at
least let things work.

Reviewed-by: Tomasz Figa <tfiga@...omium.org>

Best regards,
Tomasz