linux-kernel - RE: [PATCH v5 7/7] iommu/exynos: Use device dependency links to control runtime pm

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Date:   Sun, 23 Oct 2016 15:19:52 +0530
From:   "Sricharan" <sricharan@...eaurora.org>
To:     "'Marek Szyprowski'" <m.szyprowski@...sung.com>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <iommu@...ts.linux-foundation.org>,
        <linux-samsung-soc@...r.kernel.org>
Cc:     "'Tomeu Vizoso'" <tomeu.vizoso@...labora.com>,
        "'Bartlomiej Zolnierkiewicz'" <b.zolnierkie@...sung.com>,
        "'Greg Kroah-Hartman'" <gregkh@...uxfoundation.org>,
        "'Kevin Hilman'" <khilman@...nel.org>,
        "'Rafael J. Wysocki'" <rjw@...ysocki.net>,
        "'Tomasz Figa'" <tomasz.figa@...il.com>,
        "'Krzysztof Kozlowski'" <krzk@...nel.org>,
        "'Inki Dae'" <inki.dae@...sung.com>,
        "'Tobias Jakobi'" <tjakobi@...h.uni-bielefeld.de>,
        "'Luis R. Rodriguez'" <mcgrof@...nel.org>,
        "'Kukjin Kim'" <kgene@...nel.org>,
        "'Mark Brown'" <broonie@...nel.org>,
        "'Lukas Wunner'" <lukas@...ner.de>
Subject: RE: [PATCH v5 7/7] iommu/exynos: Use device dependency links to control        runtime pm

Hi Marek,
>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@...sung.com>
>---
> 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 ?

Regards,
 Sricharan