drm/msm: Reference count address spaces

There are reasons for a memory object to outlive the file descriptor
that created it and so the address space that a buffer object is
attached to must also outlive the file descriptor. Reference count
the address space so that it can remain viable until all the objects
have released their addresses.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

1 files changed, 26 insertions, 9 deletions

diff --git a/drivers/gpu/drm/msm/msm_gem_vma.c b/drivers/gpu/drm/msm/msm_gem_vma.c
index b654eca7636a..f285d7e210db 100644
--- a/drivers/gpu/drm/msm/msm_gem_vma.c
+++ b/drivers/gpu/drm/msm/msm_gem_vma.c
@@ -19,6 +19,25 @@
 #include "msm_gem.h"
 #include "msm_mmu.h"
 
+static void
+msm_gem_address_space_destroy(struct kref *kref)
+{
+	struct msm_gem_address_space *aspace = container_of(kref,
+			struct msm_gem_address_space, kref);
+
+	drm_mm_takedown(&aspace->mm);
+	if (aspace->mmu)
+		aspace->mmu->funcs->destroy(aspace->mmu);
+	kfree(aspace);
+}
+
+
+void msm_gem_address_space_put(struct msm_gem_address_space *aspace)
+{
+	if (aspace)
+		kref_put(&aspace->kref, msm_gem_address_space_destroy);
+}
+
 void
 msm_gem_unmap_vma(struct msm_gem_address_space *aspace,
 		struct msm_gem_vma *vma, struct sg_table *sgt)
@@ -34,6 +53,8 @@ msm_gem_unmap_vma(struct msm_gem_address_space *aspace,
 	drm_mm_remove_node(&vma->node);
 
 	vma->iova = 0;
+
+	msm_gem_address_space_put(aspace);
 }
 
 int
@@ -57,16 +78,10 @@ msm_gem_map_vma(struct msm_gem_address_space *aspace,
 				size, IOMMU_READ | IOMMU_WRITE);
 	}
 
-	return ret;
-}
+	/* Get a reference to the aspace to keep it around */
+	kref_get(&aspace->kref);
 
-void
-msm_gem_address_space_destroy(struct msm_gem_address_space *aspace)
-{
-	drm_mm_takedown(&aspace->mm);
-	if (aspace->mmu)
-		aspace->mmu->funcs->destroy(aspace->mmu);
-	kfree(aspace);
+	return ret;
 }
 
 struct msm_gem_address_space *
@@ -85,5 +100,7 @@ msm_gem_address_space_create(struct device *dev, struct iommu_domain *domain,
 	drm_mm_init(&aspace->mm, (domain->geometry.aperture_start >> PAGE_SHIFT),
 			(domain->geometry.aperture_end >> PAGE_SHIFT) - 1);
 
+	kref_init(&aspace->kref);
+
 	return aspace;
 }