Re: [PATCH v2 09/13] iommu/rockchip: Use iommu_group_get_for_dev() for add_device

Robin Murphy
2018-01-17T12:31:05Z

On 16/01/18 13:25, Jeffy Chen wrote:
> IOMMU drivers are supposed to call this function instead of manually
> creating a group in their .add_device callback. This behavior is not
> strictly required by ARM DMA mapping implementation, but ARM64 already
> relies on it. This patch fixes the rockchip-iommu driver to comply with
> this requirement.

FWIW that's not 100% true: what arm64 relies on is the group having a
default DMA ops domain. Technically, you *could* open-code that in the
driver's group allocation, but obviously using the appropriate existing
API is nicer :)

[...]
> @@ -1182,6 +1164,29 @@ static void rk_iommu_remove_device(struct device *dev)
> iommu_group_remove_device(dev);
> }
>
> +static struct iommu_group *rk_iommu_device_group(struct device *dev)
> +{
> + struct iommu_group *group;
> + int ret;
> +
> + group = iommu_group_get(dev);
> + if (!group) {

This check is pointless - if dev->iommu_group were non-NULL you wouldn't
have been called in the first place.

Robin.

> + group = iommu_group_alloc();
> + if (IS_ERR(group))
> + return group;
> + }
> +
> + ret = rk_iommu_group_set_iommudata(group, dev);
> + if (ret)
> + goto err_put_group;
> +
> + return group;
> +
> +err_put_group:
> + iommu_group_put(group);
> + return ERR_PTR(ret);
> +}
> +
> static const struct iommu_ops rk_iommu_ops = {
> .domain_alloc = rk_iommu_domain_alloc,
> .domain_free = rk_iommu_domain_free,
> @@ -1193,6 +1198,7 @@ static const struct iommu_ops rk_iommu_ops = {
> .add_device = rk_iommu_add_device,
> .remove_device = rk_iommu_remove_device,
> .iova_to_phys = rk_iommu_iova_to_phys,
> + .device_group = rk_iommu_device_group,
> .pgsize_bitmap = RK_IOMMU_PGSIZE_BITMAP,
> };
>
>