[PATCH] iommu/exynos: Fix set_platform_dma_ops() callback

[PATCH] iommu/exynos: Fix set_platform_dma_ops() callback

[Marek Szyprowski]

There are some subtle differences between release_device() and
set_platform_dma_ops() callbacks, so separate those two callbacks. Device
links should be removed only in release_device(), because they were
created in probe_device(). While fixing this, remove the conditional code
as it is not really needed.

Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
Fixes: 189d496b48b1 ("iommu/exynos: Add missing set_platform_dma_ops callback")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/iommu/exynos-iommu.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
index 483aaaeb6dae..4141625542ef 100644
--- a/drivers/iommu/exynos-iommu.c
+++ b/drivers/iommu/exynos-iommu.c
@@ -1415,23 +1415,26 @@ static struct iommu_device *exynos_iommu_probe_device(struct device *dev)
 	return &data->iommu;
 }
 
-static void exynos_iommu_release_device(struct device *dev)
+static void exynos_iommu_set_platform_dma(struct device *dev)
 {
 	struct exynos_iommu_owner *owner = dev_iommu_priv_get(dev);
-	struct sysmmu_drvdata *data;
 
 	if (owner->domain) {
 		struct iommu_group *group = iommu_group_get(dev);
 
 		if (group) {
-#ifndef CONFIG_ARM
-			WARN_ON(owner->domain !=
-				iommu_group_default_domain(group));
-#endif
 			exynos_iommu_detach_device(owner->domain, dev);
 			iommu_group_put(group);
 		}
 	}
+}
+
+static void exynos_iommu_release_device(struct device *dev)
+{
+	struct exynos_iommu_owner *owner = dev_iommu_priv_get(dev);
+	struct sysmmu_drvdata *data;
+
+	exynos_iommu_set_platform_dma(dev);
 
 	list_for_each_entry(data, &owner->controllers, owner_node)
 		device_link_del(data->link);
@@ -1478,11 +1481,9 @@ static int exynos_iommu_of_xlate(struct device *dev,
 static const struct iommu_ops exynos_iommu_ops = {
 	.domain_alloc = exynos_iommu_domain_alloc,
 	.device_group = generic_device_group,
-#ifdef CONFIG_ARM
-	.set_platform_dma_ops = exynos_iommu_release_device,
-#endif
 	.probe_device = exynos_iommu_probe_device,
 	.release_device = exynos_iommu_release_device,
+	.set_platform_dma_ops = exynos_iommu_set_platform_dma,
 	.pgsize_bitmap = SECT_SIZE | LPAGE_SIZE | SPAGE_SIZE,
 	.of_xlate = exynos_iommu_of_xlate,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
-- 
2.39.1

Re: [PATCH] iommu/exynos: Fix set_platform_dma_ops() callback

[Baolu Lu]

On 2023/2/17 19:21, Marek Szyprowski wrote:
> There are some subtle differences between release_device() and
> set_platform_dma_ops() callbacks, so separate those two callbacks. Device
> links should be removed only in release_device(), because they were
> created in probe_device(). While fixing this, remove the conditional code
> as it is not really needed.
> 
> Reported-by: Jason Gunthorpe<jgg@ziepe.ca>
> Fixes: 189d496b48b1 ("iommu/exynos: Add missing set_platform_dma_ops callback")

The exynos iommu driver actually supports default domain. Why need to
add the set_platform_dma_ops?

  897 static struct iommu_domain *exynos_iommu_domain_alloc(unsigned type)
  898 {
  899         struct exynos_iommu_domain *domain;
  900         dma_addr_t handle;
  901         int i;
  902
  903         /* Check if correct PTE offsets are initialized */
  904         BUG_ON(PG_ENT_SHIFT < 0 || !dma_dev);
  905
  906         if (type != IOMMU_DOMAIN_DMA && type != 
IOMMU_DOMAIN_UNMANAGED)
  907                 return NULL;

It actually doesn't support identity default domain. But the iommu core
allows this and roll back to DMA domain instead.

1686 static int iommu_group_alloc_default_domain(struct iommu_group *group,
1687                                             struct device *dev,
1688                                             unsigned int type)
1689 {
1690         struct iommu_domain *dom;
1691
1692         dom = __iommu_domain_alloc(dev, type);
1693         if (!dom && type != IOMMU_DOMAIN_DMA) {
1694                 dom = __iommu_domain_alloc(dev, IOMMU_DOMAIN_DMA);
1695                 if (dom)
1696                         pr_warn("Failed to allocate default IOMMU 
domain of type %u for group %s - Falling back to IOMMU_DOMAIN_D     MA", 

1697                                 type, group->name);
1698         }

I have a feeling, set_platform_dma_ops was mistakenly added to fix other
problems instead of missing a callback.

Best regards,
baolu

Re: [PATCH] iommu/exynos: Fix set_platform_dma_ops() callback

[Jason Gunthorpe]

On Fri, Feb 17, 2023 at 12:21:29PM +0100, Marek Szyprowski wrote:
> There are some subtle differences between release_device() and
> set_platform_dma_ops() callbacks, so separate those two callbacks. Device
> links should be removed only in release_device(), because they were
> created in probe_device(). While fixing this, remove the conditional code
> as it is not really needed.
> 
> Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
> Fixes: 189d496b48b1 ("iommu/exynos: Add missing set_platform_dma_ops callback")
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/iommu/exynos-iommu.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> index 483aaaeb6dae..4141625542ef 100644
> --- a/drivers/iommu/exynos-iommu.c
> +++ b/drivers/iommu/exynos-iommu.c
> @@ -1415,23 +1415,26 @@ static struct iommu_device *exynos_iommu_probe_device(struct device *dev)
>  	return &data->iommu;
>  }
>  
> -static void exynos_iommu_release_device(struct device *dev)
> +static void exynos_iommu_set_platform_dma(struct device *dev)
>  {
>  	struct exynos_iommu_owner *owner = dev_iommu_priv_get(dev);
> -	struct sysmmu_drvdata *data;
>  
>  	if (owner->domain) {
>  		struct iommu_group *group = iommu_group_get(dev);
>  
>  		if (group) {
> -#ifndef CONFIG_ARM
> -			WARN_ON(owner->domain !=
> -				iommu_group_default_domain(group));
> -#endif
>  			exynos_iommu_detach_device(owner->domain, dev);
>  			iommu_group_put(group);
>  		}
>  	}

See, this is my confusion from the other email, all this does is
"detach_device" but it really should restore the arm_iommu's
mapping->domain.

> @@ -1478,11 +1481,9 @@ static int exynos_iommu_of_xlate(struct device *dev,
>  static const struct iommu_ops exynos_iommu_ops = {
>  	.domain_alloc = exynos_iommu_domain_alloc,
>  	.device_group = generic_device_group,
> -#ifdef CONFIG_ARM
> -	.set_platform_dma_ops = exynos_iommu_release_device,
> -#endif
>  	.probe_device = exynos_iommu_probe_device,
>  	.release_device = exynos_iommu_release_device,
> +	.set_platform_dma_ops = exynos_iommu_set_platform_dma,

The ifdef is still needed, when using default domains this op should
not be set at all.

Jason