linux-kernel - Re: [PATCH v5 1/6] base: power: runtime: Export pm_runtime_get/put

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Message-ID: <CAJZ5v0h-+r3_xxjkgavza8SLAKSnUsXCRqn7PHxSVpeVnCkwHA@mail.gmail.com>
Date:   Thu, 11 Jan 2018 23:53:11 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.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>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Clark <robdclark@...il.com>,
        Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        "open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno@...ts.freedesktop.org, Len Brown <len.brown@...el.com>,
        Pavel Machek <pavel@....cz>, David Airlie <airlied@...ux.ie>,
        Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        architt@...eaurora.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v5 1/6] base: power: runtime: Export pm_runtime_get/put_suppliers

On Tue, Jan 9, 2018 at 11:01 AM, Vivek Gautam
<vivek.gautam@...eaurora.org> wrote:
> The device link allows the pm framework to tie the supplier and
> consumer. So, whenever the consumer is powered-on the supplier
> is powered-on first.
>
> There are however cases in which the consumer wants to power-on
> the supplier, but not itself.
> E.g., A Graphics or multimedia driver wants to power-on the SMMU
> to unmap a buffer and finish the TLB operations without powering
> on itself. Some of these unmap requests are coming from the
> user space when the controller itself is not powered-up, and it
> can be huge penalty in terms of power and latency to power-up
> the graphics/mm controllers.
> There can be an argument that the supplier should handle this case
> on its own and there should not be a need for the consumer to
> power-on the supplier. But as discussed on the thread [1] about
> ARM-SMMU runtime pm, we don't want to introduce runtime pm calls
> in atomic path in arm_smmu_unmap.
>
> [1] https://patchwork.kernel.org/patch/9827825/
>
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Please feel free to route this along with the rest of the series.

Thanks!

> ---
>
>  * This is v2 of the patch [1]. Adding it to this patch series.
>    [1] https://patchwork.kernel.org/patch/10102447/
>
>  drivers/base/power/runtime.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 6e89b51ea3d9..06a2a88fe866 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -1579,6 +1579,7 @@ void pm_runtime_get_suppliers(struct device *dev)
>
>         device_links_read_unlock(idx);
>  }
> +EXPORT_SYMBOL_GPL(pm_runtime_get_suppliers);
>
>  /**
>   * pm_runtime_put_suppliers - Drop references to supplier devices.
> @@ -1597,6 +1598,7 @@ void pm_runtime_put_suppliers(struct device *dev)
>
>         device_links_read_unlock(idx);
>  }
> +EXPORT_SYMBOL_GPL(pm_runtime_put_suppliers);
>
>  void pm_runtime_new_link(struct device *dev)
>  {
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>