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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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