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

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Date:   Thu, 1 Feb 2018 14:23:11 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Robin Murphy <robin.murphy@....com>, 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

Hi,


On 1/31/2018 6:39 PM, Robin Murphy wrote:
> 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)?

Right. Will add device_link_del() call. Thanks for pointing out.

regards
Vivek

>
> 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:
>>