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    SubjectRe: [PATCH v9 4/5] iommu/arm-smmu: Add the device_link between masters and smmu
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    On 13/03/18 08:55, Vivek Gautam wrote:
    > From: Sricharan R <sricharan@codeaurora.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@codeaurora.org>
    > Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
    > Reviewed-by: Tomasz Figa <tfiga@chromium.org>
    > ---
    > drivers/iommu/arm-smmu.c | 29 +++++++++++++++++++++++++++++
    > 1 file changed, 29 insertions(+)
    >
    > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
    > index 56a04ae80bf3..64953ff2281f 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) {

    FWIW, given that we don't really care about link itself, I'd be quite
    happy to simplify that lot down to:

    if (pm_runtime_enabled(smmu_dev) &&
    !device_link_add(dev, smmu->dev, DL_FLAG_PM_RUNTIME)) {

    > + dev_warn(smmu->dev,
    > + "Unable to add link to the consumer %s\n",
    > + dev_name(dev));

    (side note: since device_link_add() already prints a message on success,
    maybe it could print its own failure message too?)

    Robin.

    > + ret = -ENODEV;
    > + goto out_unlink;
    > + }
    > + }
    > +
    > arm_smmu_rpm_put(smmu);
    >
    > return 0;
    >
    > +out_unlink:
    > + iommu_device_unlink(&smmu->iommu, dev);
    > + arm_smmu_master_free_smes(fwspec);
    > out_rpm_put:
    > arm_smmu_rpm_put(smmu);
    > out_cfg_free:
    > @@ -1486,6 +1507,14 @@ static void arm_smmu_remove_device(struct device *dev)
    > cfg = fwspec->iommu_priv;
    > smmu = cfg->smmu;
    >
    > + if (pm_runtime_enabled(smmu->dev)) {
    > + struct device_link *link;
    > +
    > + link = device_link_find(dev, smmu->dev);
    > + if (link)
    > + device_link_del(link);
    > + }
    > +
    > ret = arm_smmu_rpm_get(smmu);
    > if (ret < 0)
    > return;
    >

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