drm/msm: Count how many times iova memory is pinned

Add a reference count to track how many times a particular
chunk of iova memory is pinned (mapped) in the iomu and
add msm_gem_unpin_iova to give up references.

It is important to note that msm_gem_unpin_iova replaces
msm_gem_put_iova because the new implicit behavior
that an assigned iova in a given vma is now valid for the
life of the buffer and what we are really focusing on is
the use of that iova.

For now the unmappings are lazy; once the reference counts
go to zero they *COULD* be unmapped dynamically but that
will require an outside force such as a shrinker or
mm_notifiers.  For now, we're just focusing on getting
the counting right and setting ourselves up to be ready
for the future.

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

1 files changed, 39 insertions, 12 deletions

diff --git a/drivers/gpu/drm/msm/msm_gem_vma.c b/drivers/gpu/drm/msm/msm_gem_vma.c
index c4c42bf0db0e..ee46d8321b05 100644
--- a/drivers/gpu/drm/msm/msm_gem_vma.c
+++ b/drivers/gpu/drm/msm/msm_gem_vma.c
@@ -38,26 +38,32 @@ void msm_gem_address_space_put(struct msm_gem_address_space *aspace)
 		kref_put(&aspace->kref, msm_gem_address_space_destroy);
 }
 
-void
-msm_gem_unmap_vma(struct msm_gem_address_space *aspace,
+/* Actually unmap memory for the vma */
+void msm_gem_purge_vma(struct msm_gem_address_space *aspace,
 		struct msm_gem_vma *vma)
 {
-	if (!aspace || !vma->iova)
+	unsigned size = vma->node.size << PAGE_SHIFT;
+
+	/* Print a message if we try to purge a vma in use */
+	if (WARN_ON(vma->inuse > 0))
 		return;
 
-	if (aspace->mmu) {
-		unsigned size = vma->node.size << PAGE_SHIFT;
-		aspace->mmu->funcs->unmap(aspace->mmu, vma->iova, size);
-	}
+	/* Don't do anything if the memory isn't mapped */
+	if (!vma->mapped)
+		return;
 
-	spin_lock(&aspace->lock);
-	drm_mm_remove_node(&vma->node);
-	spin_unlock(&aspace->lock);
+	if (aspace->mmu)
+		aspace->mmu->funcs->unmap(aspace->mmu, vma->iova, size);
 
-	vma->iova = 0;
 	vma->mapped = false;
+}
 
-	msm_gem_address_space_put(aspace);
+/* Remove reference counts for the mapping */
+void msm_gem_unmap_vma(struct msm_gem_address_space *aspace,
+		struct msm_gem_vma *vma)
+{
+	if (!WARN_ON(!vma->iova))
+		vma->inuse--;
 }
 
 int
@@ -70,6 +76,9 @@ msm_gem_map_vma(struct msm_gem_address_space *aspace,
 	if (WARN_ON(!vma->iova))
 		return -EINVAL;
 
+	/* Increase the usage counter */
+	vma->inuse++;
+
 	if (vma->mapped)
 		return 0;
 
@@ -85,6 +94,23 @@ msm_gem_map_vma(struct msm_gem_address_space *aspace,
 	return ret;
 }
 
+/* Close an iova.  Warn if it is still in use */
+void msm_gem_close_vma(struct msm_gem_address_space *aspace,
+		struct msm_gem_vma *vma)
+{
+	if (WARN_ON(vma->inuse > 0 || vma->mapped))
+		return;
+
+	spin_lock(&aspace->lock);
+	if (vma->iova)
+		drm_mm_remove_node(&vma->node);
+	spin_unlock(&aspace->lock);
+
+	vma->iova = 0;
+
+	msm_gem_address_space_put(aspace);
+}
+
 /* Initialize a new vma and allocate an iova for it */
 int msm_gem_init_vma(struct msm_gem_address_space *aspace,
 		struct msm_gem_vma *vma, int npages)
@@ -109,6 +135,7 @@ int msm_gem_init_vma(struct msm_gem_address_space *aspace,
 	return 0;
 }
 
+
 struct msm_gem_address_space *
 msm_gem_address_space_create(struct device *dev, struct iommu_domain *domain,
 		const char *name)