linux-kernel - Re: [PATCH v5 2/2] iommu/exynos: Add iommu driver for Exynos Platforms

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Message-ID: <20111014141714.GD2198@amd.com>
Date:	Fri, 14 Oct 2011 16:17:14 +0200
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	KyongHo Cho <pullip.cho@...sung.com>
CC:	'Linux ARM Kernel' <linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	'Russell King' <rmk+kernel@....linux.org.uk>,
	'Ohad Ben-Cohen' <ohad@...ery.com>,
	'Sanghyun Lee' <sanghyun75.lee@...sung.com>,
	"younglak1004.kim@...sung.com" <younglak1004.kim@...sung.com>,
	'Kukjin Kim' <kgene.kim@...sung.com>
Subject: Re: [PATCH v5 2/2] iommu/exynos: Add iommu driver for Exynos
 Platforms

On Thu, Oct 13, 2011 at 04:13:23AM -0400, KyongHo Cho wrote:
> +struct exynos_iommu_domain {
> +       struct device *dev;
> +       unsigned long *pgtable;
> +       spinlock_t lock;
> +       spinlock_t pgtablelock;
> +};

Can you please add comments to document what these spinlocks protect?

> +static int exynos_iommu_attach_device(struct iommu_domain *domain,
> +                                  struct device *dev)
> +{
> +       struct exynos_iommu_domain *priv = domain->priv;
> +       int ret;
> +
> +       spin_lock(&priv->lock);
> +
> +       priv->dev = dev;
> +
> +       spin_unlock(&priv->lock);
> +
> +       ret = exynos_iommu_enable(domain);
> +
> +       return ret;
> +}
> +
> +static void exynos_iommu_detach_device(struct iommu_domain *domain,
> +                                   struct device *dev)
> +{
> +       struct exynos_iommu_domain *priv = domain->priv;
> +
> +       spin_lock(&priv->lock);
> +
> +       if (priv->dev == dev) {
> +               priv->dev = NULL;
> +
> +               spin_unlock(&priv->lock);
> +
> +               exynos_iommu_disable(domain);
> +       } else {
> +               spin_unlock(&priv->lock);
> +       }
> +}

That looks weird. As I read this code there is a 1-1 mapping between a
device and a domain. This breaks semantics of the iommu-api where a
domain can contain multiple devices.


	Joerg

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