linux-kernel - Re: [PATCH 1/4] IOMMU: Make dwo drivers use stateless device links

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Date:   Tue, 29 Jan 2019 09:55:52 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <jroedel@...e.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Lukas Wunner <lukas@...ner.de>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Lucas Stach <l.stach@...gutronix.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jeffy Chen <jeffy.chen@...k-chips.com>
Subject: Re: [PATCH 1/4] IOMMU: Make dwo drivers use stateless device links

Hi Rafael,

On 2019-01-29 00:05, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> The device links used by rockchip-iommu and exynos-iommu are
> completely managed by these drivers within the IOMMU framework,
> so there is no reason to involve the driver core in the management
> of these links.
>
> For this reason, make rockchip-iommu and exynos-iommu pass
> DL_FLAG_STATELESS in flags to device_link_add(), so that the device
> links used by them are stateless.
>
> [Note that this change is requisite for a subsequent one that will
>  rework the management of stateful device links in the driver core
>  and it will not be compatible with the two drivers in question any
>  more.]
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Indeed there is no need to use driver-state tracking feature of device
links in this case.

For the Exynos IOMMU driver:

Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>

> ---
>  drivers/iommu/exynos-iommu.c   |    1 +
>  drivers/iommu/rockchip-iommu.c |    3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/iommu/rockchip-iommu.c
> ===================================================================
> --- linux-pm.orig/drivers/iommu/rockchip-iommu.c
> +++ linux-pm/drivers/iommu/rockchip-iommu.c
> @@ -1071,7 +1071,8 @@ static int rk_iommu_add_device(struct de
>  	iommu_group_put(group);
>  
>  	iommu_device_link(&iommu->iommu, dev);
> -	data->link = device_link_add(dev, iommu->dev, DL_FLAG_PM_RUNTIME);
> +	data->link = device_link_add(dev, iommu->dev,
> +				     DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME);
>  
>  	return 0;
>  }
> Index: linux-pm/drivers/iommu/exynos-iommu.c
> ===================================================================
> --- linux-pm.orig/drivers/iommu/exynos-iommu.c
> +++ linux-pm/drivers/iommu/exynos-iommu.c
> @@ -1260,6 +1260,7 @@ static int exynos_iommu_add_device(struc
>  		 * direct calls to pm_runtime_get/put in this driver.
>  		 */
>  		data->link = device_link_add(dev, data->sysmmu,
> +					     DL_FLAG_STATELESS |
>  					     DL_FLAG_PM_RUNTIME);
>  	}
>  	iommu_group_put(group);
>
>
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland