Re: [PATCH v5 7/7] iommu/exynos: Use device dependency links to control runtime pm

[Marek Szyprowski]

Hi Sricharan,


On 2016-10-24 14:29, Sricharan wrote:
> > > > This patch uses recently introduced device dependency links to track the
> > > > runtime pm state of the master's device. This way each SYSMMU controller
> > > > is set to runtime active only when its master's device is active and can
> > > > restore or save its state instead of being activated all the time when
> > > > attached to the given master device. This way SYSMMU controllers no longer
> > > > prevents respective power domains to be turned off when master's device
> > > > is not being used.
> > > >
> > > > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > > > ---
> > > > drivers/iommu/exynos-iommu.c | 16 ++++++++--------
> > > > 1 file changed, 8 insertions(+), 8 deletions(-)
> > > >
> > > > 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>;".

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland