linux-kernel - Re: [PATCH v10 4/5] iommu/arm-smmu: Add the device

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Date:   Fri, 16 Mar 2018 15:41:29 +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>,
        rafael.j.wysocki@...el.com, Robin Murphy <robin.murphy@....com>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        Rob Clark <robdclark@...il.com>,
        Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <linux-arm-kernel@...ts.infradead.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v10 4/5] iommu/arm-smmu: Add the device_link between
 masters and smmu

Hi Vivek,

On Wed, Mar 14, 2018 at 5:14 PM, Vivek Gautam
<vivek.gautam@...eaurora.org> wrote:
> From: Sricharan R <sricharan@...eaurora.org>
>
> Finally add the device link between the master device and
> smmu, so that the smmu gets runtime enabled/disabled only when the
> master needs it. This is done from add_device callback which gets
> called once when the master is added to the smmu.
>
> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> Reviewed-by: Tomasz Figa <tfiga@...omium.org>
> ---
>
> Changes since v9:
>  - Using device_link_del_dev() to delete the device link, instead of
>    doing it in two steps - device_link_find() to first find the link, and
>    then calling device_link_del().
>
>  drivers/iommu/arm-smmu.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 56a04ae80bf3..4cf270ffd449 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1460,10 +1460,31 @@ static int arm_smmu_add_device(struct device *dev)
>
>         iommu_device_link(&smmu->iommu, dev);
>
> +       if (pm_runtime_enabled(smmu->dev)) {
> +               struct device_link *link;
> +
> +               /*
> +                * Establish the link between smmu and master, so that the
> +                * smmu gets runtime enabled/disabled as per the master's
> +                * needs.
> +                */
> +               link = device_link_add(dev, smmu->dev, DL_FLAG_PM_RUNTIME);
> +               if (!link) {
> +                       dev_warn(smmu->dev,
> +                                "Unable to add link to the consumer %s\n",
> +                                dev_name(dev));
> +                       ret = -ENODEV;
> +                       goto out_unlink;
> +               }
> +       }

If it's an error, we should use dev_err(). Also, as per Robin's
comment for v9 could we make it as follows?

if (pm_runtime_enabled(smmu->dev) &&
    !device_link_add(dev, smmu->dev, DL_FLAG_PM_RUNTIME)) {
        dev_err(smmu->dev,
                         "Unable to add link to the consumer %s\n",
dev_name(dev));
        ret = -ENODEV;
        goto out_unlink;
}

Best regards,
Tomasz