linux-kernel - Re: [PATCH v5 5/6] iommu/mediatek: Add mt8173 IOMMU driver

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Message-ID: <20151014125309.GO27420@8bytes.org>
Date:	Wed, 14 Oct 2015 14:53:09 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Yong Wu <yong.wu@...iatek.com>
Cc:	Thierry Reding <treding@...dia.com>,
	Mark Rutland <mark.rutland@....com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Robin Murphy <robin.murphy@....com>,
	Will Deacon <will.deacon@....com>,
	Daniel Kurtz <djkurtz@...gle.com>,
	Tomasz Figa <tfiga@...gle.com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Rob Herring <robh+dt@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-mediatek@...ts.infradead.org,
	Sasha Hauer <kernel@...gutronix.de>,
	srv_heupstream@...iatek.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	iommu@...ts.linux-foundation.org, pebolle@...cali.nl,
	arnd@...db.de, mitchelh@...eaurora.org,
	Sricharan R <sricharan@...eaurora.org>, youhua.li@...iatek.com,
	k.zhang@...iatek.com, kendrick.hsu@...iatek.com
Subject: Re: [PATCH v5 5/6] iommu/mediatek: Add mt8173 IOMMU driver

On Fri, Oct 09, 2015 at 10:23:07AM +0800, Yong Wu wrote:
> +	/*
> +	 * There is a domain for each a iommu device in normal case.
> +	 * But MTK only has one iommu domain called the m4u domain which all
> +	 * the multimedia HW share. Here we reserve one as the m4u domain and
> +	 * free the others.
> +	 *
> +	 * And the attach_device that from __iommu_setup_dma_ops
> +	 * will be called earlier than probe.
> +	 */

Okay, with this being the case, you need to put all devices behind one
IOMMU into the same iommu-group, because the IOMMU can't really isolate
the devices from each other.

> +static int mtk_iommu_add_device(struct device *dev)
> +{
> +	struct iommu_group *group;
> +	struct mtk_iommu_client_priv *priv;
> +	struct mtk_iommu_domain *m4udom;
> +	struct iommu_domain *domain;
> +	int ret;
> +
> +	if (!dev->archdata.iommu) /* Not a iommu client device */
> +		return -ENODEV;
> +
> +	group = iommu_group_get(dev);
> +	if (!group) {
> +		group = iommu_group_alloc();
> +		if (IS_ERR(group)) {
> +			dev_err(dev, "Failed to allocate IOMMU group\n");
> +			return PTR_ERR(group);
> +		}
> +	}
> +
> +	ret = iommu_group_add_device(group, dev);
> +	if (ret) {
> +		dev_err(dev, "Failed to add IOMMU group\n");
> +		goto err_group_put;
> +	}
> +
> +	domain = iommu_get_domain_for_dev(dev);
> +	if (!domain) {
> +		/*
> +		 * Get the m4u iommu domain from the m4u device.
> +		 * Attach all the client devices into the m4u domain.
> +		 */
> +		priv = dev->archdata.iommu;
> +		m4udom = dev_get_drvdata(priv->m4udev);
> +		ret = iommu_attach_group(&m4udom->domain, group);
> +		if (ret)
> +			dev_err(dev, "Failed to attach IOMMU group\n");
> +	}
> +
> +err_group_put:
> +	iommu_group_put(group);
> +	return ret;
> +}

Here it looks like you are allocating one group for each device. As I
said, all devices need to be in one group.



	Joerg

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