linux-kernel - Re: [PATCH v6 7/7] iommu/exynos: Use device dependency links to control runtime pm

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Date:   Thu, 10 Nov 2016 00:31:26 +0100
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org,
        linux-samsung-soc@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
        Inki Dae <inki.dae@...sung.com>, Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Mark Brown <broonie@...nel.org>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Lukas Wunner <lukas@...ner.de>,
        Kevin Hilman <khilman@...nel.org>,
        Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Grant Likely <grant.likely@...retlab.ca>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>
Subject: Re: [PATCH v6 7/7] iommu/exynos: Use device dependency links to
 control runtime pm

On Tue, Nov 08, 2016 at 02:29:24PM +0100, Marek Szyprowski wrote:
> This patch uses recently introduced device dependency links to track the
> runtime pm state of the master's device. The goal is to let SYSMMU
> controller device's runtime PM to follow the runtime PM state of the
> respective master's device. This way each SYSMMU controller is active
> only when its master's device is active and can properly restore or save
> its state instead on runtime PM transition of master's device.
> This approach replaces old behavior, when SYSMMU controller was set to
> runtime active once after attaching to the master device. In the new
> approach SYSMMU controllers no longer prevents respective power domains
> to be turned off when master's device is not being used.
> 
> The dependency links also enforces proper order of suspending/restoring
> devices during system sleep transition, so there is no more need to use
> LATE_SYSTEM_SLEEP_PM_OPS-based workaround for ensuring that SYSMMUs are
> suspended after their master devices.

Patches 1-6 seems reasonable to me, however in so far as this patch is
concerned I'd appreaciate if you and Rafael can reply to Lukas Wunner's
questions.

  Luis

> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>  drivers/iommu/exynos-iommu.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> index 5e6d7bb..4b05a15 100644
> --- a/drivers/iommu/exynos-iommu.c
> +++ b/drivers/iommu/exynos-iommu.c
> @@ -633,8 +633,8 @@ static int __maybe_unused exynos_sysmmu_resume(struct device *dev)
>  
>  static const struct dev_pm_ops sysmmu_pm_ops = {
>  	SET_RUNTIME_PM_OPS(exynos_sysmmu_suspend, exynos_sysmmu_resume, NULL)
> -	SET_LATE_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> -				     pm_runtime_force_resume)
> +	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> +				pm_runtime_force_resume)
>  };
>  
>  static const struct of_device_id sysmmu_of_match[] __initconst = {
> @@ -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);
> +
>  	return 0;
>  }
>  
> -- 
> 1.9.1
> 
> 

-- 
Luis Rodriguez, SUSE LINUX GmbH
Maxfeldstrasse 5; D-90409 Nuernberg