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SubjectRE: [PATCH v5 7/7] iommu/exynos: Use device dependency links to control runtime pm
Date
Hi Marek,

>>>>> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
>>>>> index 5e6d7bbf9b70..59b4f2ce4f5f 100644
>>>>> --- a/drivers/iommu/exynos-iommu.c
>>>>> +++ b/drivers/iommu/exynos-iommu.c
>>>>> @@ -781,10 +781,6 @@ static void exynos_iommu_detach_device(struct iommu_domain *iommu_domain,
>>>>> if (!has_sysmmu(dev) || owner->domain != iommu_domain)
>>>>> return;
>>>>>
>>>>> - list_for_each_entry(data, &owner->controllers, owner_node) {
>>>>> - pm_runtime_put_sync(data->sysmmu);
>>>>> - }
>>>>> -
>>>>> mutex_lock(&owner->rpm_lock);
>>>>>
>>>>> list_for_each_entry(data, &owner->controllers, owner_node) {
>>>>> @@ -848,10 +844,6 @@ static int exynos_iommu_attach_device(struct iommu_domain *iommu_domain,
>>>>>
>>>>> mutex_unlock(&owner->rpm_lock);
>>>>>
>>>>> - list_for_each_entry(data, &owner->controllers, owner_node) {
>>>>> - pm_runtime_get_sync(data->sysmmu);
>>>>> - }
>>>>> -
>>>>> dev_dbg(dev, "%s: Attached IOMMU with pgtable %pa\n", __func__,
>>>>> &pagetable);
>>>>>
>>>>> @@ -1232,6 +1224,14 @@ static int exynos_iommu_of_xlate(struct device *dev,
>>>>>
>>>>> list_add_tail(&data->owner_node, &owner->controllers);
>>>>> data->master = dev;
>>>>> +
>>>>> + /*
>>>>> + * SYSMMU will be runtime activated via device link (dependency) to its
>>>>> + * master device, so there are no direct calls to pm_runtime_get/put
>>>>> + * in this driver.
>>>>> + */
>>>>> + device_link_add(dev, data->sysmmu, DL_FLAG_PM_RUNTIME);
>>>>> +
>>>> So in the case of master with multiple sids, this would be called multiple times
>>>> for the same master ?
>>> I don't know what is "multiple sids" case, but if given SYSMMU master
>>> device (supplier)
>>> has multiple SYSMMU controllers (consumers), then links will be created
>>> for each SYSMMU
>>> controller. Please note that this code is based on vanilla v4.9-rc1,
>>> which calls
>>> of_xlate() callback only once for every iommu for given master device.
>>> Your IOMMU
>>> deferred probe patches change this, but I already posted a fix for
>>> Exynos IOMMU driver
>>> to handle such case.
>> By multiple sids, i meant iommus = <&phandle sid1 sid2 .. sidn> case,
>> so xlate would be called multiples for the same master without deferred
>> probing also. But the fix that you showed on the other thread would work
>> here as well or maybe if you dont have masters with multiple sids you wont
>> have any issues as well.
>
>Exynos SYSMMU driver always use "#iommu-cells = <0>", so it doesn't support
>multiple sids. However there is a case with 2 SYSMMU controllers attached
>to the same master device: "iommus = <&sysmmu_mfc_l>, <&sysmmu_mfc_r>;".
>
with iommu-cells = <0> always, its ok. The case of 2 SYSMMU controllers that
is shown above is fine, as anyways both the suppliers (symmu) needs to linked
seperately. So it looks all fine.

Regards,
Sricharan

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