linux-kernel - Re: [PATCH v6 4/6] iommu/arm-smmu: Add the device

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Date:   Wed, 31 Jan 2018 13:09:40 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>,
        alex.williamson@...hat.com, robh+dt@...nel.org,
        mark.rutland@....com, rjw@...ysocki.net, will.deacon@....com,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        sboyd@...eaurora.org
Cc:     gregkh@...uxfoundation.org, sricharan@...eaurora.org,
        m.szyprowski@...sung.com, architt@...eaurora.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v6 4/6] iommu/arm-smmu: Add the device_link between
 masters and smmu

On 19/01/18 11:43, Vivek Gautam 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.

Don't we need to balance this with a device_link_del() in .remove_device 
(like exynos-iommu does)?

Robin.

> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> ---
>   drivers/iommu/arm-smmu.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 95478bfb182c..33bbcfedb896 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1367,6 +1367,7 @@ static int arm_smmu_add_device(struct device *dev)
>   	struct arm_smmu_device *smmu;
>   	struct arm_smmu_master_cfg *cfg;
>   	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +	struct device_link *link;
>   	int i, ret;
>   
>   	if (using_legacy_binding) {
> @@ -1428,6 +1429,16 @@ static int arm_smmu_add_device(struct device *dev)
>   
>   	pm_runtime_put_sync(smmu->dev);
>   
> +	/*
> +	 * 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 create device link between %s and %s\n",
> +			 dev_name(smmu->dev), dev_name(dev));
> +
>   	return 0;
>   
>   out_cfg_free:
>