linux-kernel - Re: [PATCH v2 23/33] iommu/mediatek-v1 Convert to probe/release

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Date:   Fri, 15 May 2020 15:44:59 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Joerg Roedel <joro@...tes.org>
CC:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-kernel@...r.kernel.org>, <iommu@...ts.linux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v2 23/33] iommu/mediatek-v1 Convert to
 probe/release_device() call-backs

On Tue, 2020-04-14 at 15:15 +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> Convert the Mediatek-v1 IOMMU driver to use the probe_device() and
> release_device() call-backs of iommu_ops, so that the iommu core code
> does the group and sysfs setup.
> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  drivers/iommu/mtk_iommu_v1.c | 50 +++++++++++++++---------------------
>  1 file changed, 20 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
> index a31be05601c9..7bdd74c7cb9f 100644
> --- a/drivers/iommu/mtk_iommu_v1.c
> +++ b/drivers/iommu/mtk_iommu_v1.c
> @@ -416,14 +416,12 @@ static int mtk_iommu_create_mapping(struct device *dev,
>  	return 0;
>  }
>  
> -static int mtk_iommu_add_device(struct device *dev)
> +static struct iommu_device *mtk_iommu_probe_device(struct device *dev)
>  {
>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> -	struct dma_iommu_mapping *mtk_mapping;
>  	struct of_phandle_args iommu_spec;
>  	struct of_phandle_iterator it;
>  	struct mtk_iommu_data *data;
> -	struct iommu_group *group;
>  	int err;
>  
>  	of_for_each_phandle(&it, err, dev->of_node, "iommus",
> @@ -442,35 +440,28 @@ static int mtk_iommu_add_device(struct device *dev)
>  	}
>  
>  	if (!fwspec || fwspec->ops != &mtk_iommu_ops)
> -		return -ENODEV; /* Not a iommu client device */
> +		return ERR_PTR(-ENODEV); /* Not a iommu client device */
>  
> -	/*
> -	 * This is a short-term bodge because the ARM DMA code doesn't
> -	 * understand multi-device groups, but we have to call into it
> -	 * successfully (and not just rely on a normal IOMMU API attach
> -	 * here) in order to set the correct DMA API ops on @dev.
> -	 */
> -	group = iommu_group_alloc();
> -	if (IS_ERR(group))
> -		return PTR_ERR(group);
> +	data = dev_iommu_priv_get(dev);
>  
> -	err = iommu_group_add_device(group, dev);
> -	iommu_group_put(group);
> -	if (err)
> -		return err;
> +	return &data->iommu;
> +}
>  
> -	data = dev_iommu_priv_get(dev);
> +static void mtk_iommu_probe_finalize(struct device *dev)
> +{
> +	struct dma_iommu_mapping *mtk_mapping;
> +	struct mtk_iommu_data *data;
> +	int err;
> +
> +	data        = dev_iommu_priv_get(dev);
>  	mtk_mapping = data->dev->archdata.iommu;
> -	err = arm_iommu_attach_device(dev, mtk_mapping);
> -	if (err) {
> -		iommu_group_remove_device(dev);
> -		return err;
> -	}
>  
> -	return iommu_device_link(&data->iommu, dev);
> +	err = arm_iommu_attach_device(dev, mtk_mapping);
> +	if (err)
> +		dev_err(dev, "Can't create IOMMU mapping - DMA-OPS will not work\n");


Hi Joerg,

     Thanks very much for this patch.

     This arm_iommu_attach_device is called just as we expected.

     But it will fail in this callstack as the group->mutex was tried to
be re-locked...

[<c0938e8c>] (iommu_attach_device) from [<c0317590>]
(__arm_iommu_attach_device+0x34/0x90)
[<c0317590>] (__arm_iommu_attach_device) from [<c03175f8>]
(arm_iommu_attach_device+0xc/0x20)
[<c03175f8>] (arm_iommu_attach_device) from [<c09432cc>]
(mtk_iommu_probe_finalize+0x34/0x50)
[<c09432cc>] (mtk_iommu_probe_finalize) from [<c093a8ac>]
(bus_iommu_probe+0x2a8/0x2c4)
[<c093a8ac>] (bus_iommu_probe) from [<c093a950>] (bus_set_iommu
+0x88/0xd4)
[<c093a950>] (bus_set_iommu) from [<c0943c74>] (mtk_iommu_probe
+0x2f8/0x364)


>  }
>  
> -static void mtk_iommu_remove_device(struct device *dev)
> +static void mtk_iommu_release_device(struct device *dev)
>  {
>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>  	struct mtk_iommu_data *data;
> @@ -479,9 +470,6 @@ static void mtk_iommu_remove_device(struct device *dev)
>  		return;
>  
>  	data = dev_iommu_priv_get(dev);
> -	iommu_device_unlink(&data->iommu, dev);
> -
> -	iommu_group_remove_device(dev);
>  	iommu_fwspec_free(dev);
>  }
>  
> @@ -534,8 +522,10 @@ static const struct iommu_ops mtk_iommu_ops = {
>  	.map		= mtk_iommu_map,
>  	.unmap		= mtk_iommu_unmap,
>  	.iova_to_phys	= mtk_iommu_iova_to_phys,
> -	.add_device	= mtk_iommu_add_device,
> -	.remove_device	= mtk_iommu_remove_device,
> +	.probe_device	= mtk_iommu_probe_device,
> +	.probe_finalize = mtk_iommu_probe_finalize,
> +	.release_device	= mtk_iommu_release_device,
> +	.device_group	= generic_device_group,
>  	.pgsize_bitmap	= ~0UL << MT2701_IOMMU_PAGE_SHIFT,
>  };
>