[PATCH] drm/exynos: Use selected dma_dev default iommu domain instead of a fake one

[Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>]

Instead of allocating a fake IOMMU domain for all Exynos DRM components,
simply reuse the default IOMMU domain of the already selected DMA device.
This allows some design changes in IOMMU framework without breaking IOMMU
support in Exynos DRM.

Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
Inki:
If possible, please consider this patch as a fix for v4.19-rc, this will
help doing a rework in IOMMU and DMA-IOMMU frameworks in v4.20 without
breaking Exynos DRM. It worked for current IOMMU code, but such usage is
considered as a hack.
---
 drivers/gpu/drm/exynos/exynos_drm_iommu.h | 34 ++++-------------------
 1 file changed, 6 insertions(+), 28 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_iommu.h b/drivers/gpu/drm/exynos/exynos_drm_iommu.h
index 87f6b5672e11..797d9ee5f15a 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_iommu.h
+++ b/drivers/gpu/drm/exynos/exynos_drm_iommu.h
@@ -55,37 +55,12 @@ static inline void __exynos_iommu_detach(struct exynos_drm_private *priv,
 static inline int __exynos_iommu_create_mapping(struct exynos_drm_private *priv,
 					unsigned long start, unsigned long size)
 {
-	struct iommu_domain *domain;
-	int ret;
-
-	domain = iommu_domain_alloc(priv->dma_dev->bus);
-	if (!domain)
-		return -ENOMEM;
-
-	ret = iommu_get_dma_cookie(domain);
-	if (ret)
-		goto free_domain;
-
-	ret = iommu_dma_init_domain(domain, start, size, NULL);
-	if (ret)
-		goto put_cookie;
-
-	priv->mapping = domain;
+	priv->mapping = iommu_get_domain_for_dev(priv->dma_dev);
 	return 0;
-
-put_cookie:
-	iommu_put_dma_cookie(domain);
-free_domain:
-	iommu_domain_free(domain);
-	return ret;
 }
 
 static inline void __exynos_iommu_release_mapping(struct exynos_drm_private *priv)
 {
-	struct iommu_domain *domain = priv->mapping;
-
-	iommu_put_dma_cookie(domain);
-	iommu_domain_free(domain);
 	priv->mapping = NULL;
 }
 
@@ -94,7 +69,9 @@ static inline int __exynos_iommu_attach(struct exynos_drm_private *priv,
 {
 	struct iommu_domain *domain = priv->mapping;
 
-	return iommu_attach_device(domain, dev);
+	if (dev != priv->dma_dev)
+		return iommu_attach_device(domain, dev);
+	return 0;
 }
 
 static inline void __exynos_iommu_detach(struct exynos_drm_private *priv,
@@ -102,7 +79,8 @@ static inline void __exynos_iommu_detach(struct exynos_drm_private *priv,
 {
 	struct iommu_domain *domain = priv->mapping;
 
-	iommu_detach_device(domain, dev);
+	if (dev != priv->dma_dev)
+		iommu_detach_device(domain, dev);
 }
 #else
 #error Unsupported architecture and IOMMU/DMA-mapping glue code
-- 
2.17.1