linux-kernel - Re: [PATCH 2/3] iommu: mediatek: Add support of unmanaged iommu domain

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Message-ID: <741920ba-8637-5e28-695c-699b46351590@arm.com>
Date:   Mon, 30 Jan 2023 12:04:05 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Alexandre Bailon <abailon@...libre.com>, yong.wu@...iatek.com,
        joro@...tes.org, will@...nel.org
Cc:     matthias.bgg@...il.com, krzysztof.kozlowski@...aro.org,
        robh+dt@...nel.org, iommu@...ts.linux.dev,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/3] iommu: mediatek: Add support of unmanaged iommu
 domain

On 2023-01-30 10:27, Alexandre Bailon wrote:
> Currently, the driver can allocate an unmanaged iommu domain.
> But, this only works for SoC having multiple bank or multiple iova region.

That is for good reason - there is only a single pagetable per bank, so 
if there are multiple devices assigned to a single bank, they cannot 
possibly be attached to different domains at the same time. Hence why 
the banks are modelled as groups.

Thanks,
Robin.

> This updates the driver to also support unmanaged iommu domain if
> MTK_UNMANAGED_DEVICE is set in the iommu id.
> 
> Signed-off-by: Alexandre Bailon <abailon@...libre.com>
> ---
>   drivers/iommu/mtk_iommu.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index 2badd6acfb23d..5884a1ad409a0 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -858,9 +858,15 @@ static int mtk_iommu_get_group_id(struct device *dev, const struct mtk_iommu_pla
>   static struct iommu_group *mtk_iommu_device_group(struct device *dev)
>   {
>   	struct mtk_iommu_data *c_data = dev_iommu_priv_get(dev), *data;
> +	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>   	struct list_head *hw_list = c_data->hw_list;
>   	struct iommu_group *group;
>   	int groupid;
> +	int i;
> +
> +	for (i = 0; i < fwspec->num_ids; i++)
> +		if (MTK_M4U_UNMANAGED(fwspec->ids[i]))
> +			return iommu_group_alloc();
>   
>   	data = mtk_iommu_get_frst_data(hw_list);
>   	if (!data)