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SubjectRe: [PATCH v8 4/5] iommu/arm-smmu: Add the device_link between masters and smmu
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On 02/03/18 10:10, 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>
> ---
> drivers/iommu/arm-smmu.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 3d6a1875431f..bb1ea82c1003 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -217,6 +217,9 @@ struct arm_smmu_device {
>
> /* IOMMU core code handle */
> struct iommu_device iommu;
> +
> + /* runtime PM link to master */
> + struct device_link *link;

Just the one?

> };
>
> enum arm_smmu_context_fmt {
> @@ -1470,10 +1473,26 @@ static int arm_smmu_add_device(struct device *dev)
>
> iommu_device_link(&smmu->iommu, dev);
>
> + /*
> + * Establish the link between smmu and master, so that the
> + * smmu gets runtime enabled/disabled as per the master's
> + * needs.
> + */
> + smmu->link = device_link_add(dev, smmu->dev, DL_FLAG_PM_RUNTIME);

Maybe I've misunderstood how the API works, but AFAICS the second and
subsequent devices are all just going to overwrite (and leak) the link
of the previous one...

> + if (!smmu->link) {
> + dev_warn(smmu->dev, "Unable to create device link between %s and %s\n",
> + dev_name(smmu->dev), dev_name(dev));
> + 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:
> @@ -1496,6 +1515,8 @@ static void arm_smmu_remove_device(struct device *dev)
> cfg = fwspec->iommu_priv;
> smmu = cfg->smmu;
>
> + device_link_del(smmu->link);

...and equivalently you end up with a double-free (or more) here of a
link which may not have belonged to dev anyway.

Robin.

> +
> ret = arm_smmu_rpm_get(smmu);
> if (ret < 0)
> return;
>

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