[PATCH RFC 051/111] staging: etnaviv: implement round-robin GPU MMU allocation

[Lucas Stach]

From: Russell King <rmk+kernel at arm.linux.org.uk>

In order to avoid flushing the GPU MMU every time we unmap and remap,
allocate MMU addresses in a round-robin fashion.  When we have to wrap
back to the beginning, indicate that the MMU needs to be flushed.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 drivers/staging/etnaviv/etnaviv_mmu.c | 23 +++++++++++++++++++++--
 drivers/staging/etnaviv/etnaviv_mmu.h |  1 +
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/etnaviv/etnaviv_mmu.c b/drivers/staging/etnaviv/etnaviv_mmu.c
index 4589995b83ff..4fbba26a3f37 100644
--- a/drivers/staging/etnaviv/etnaviv_mmu.c
+++ b/drivers/staging/etnaviv/etnaviv_mmu.c
@@ -117,10 +117,29 @@ int etnaviv_iommu_map_gem(struct etnaviv_iommu *mmu,
 	if (!node)
 		return -ENOMEM;
 
-	ret = drm_mm_insert_node(&mmu->mm, node, etnaviv_obj->base.size, 0,
-				 DRM_MM_SEARCH_DEFAULT);
+	while (1) {
+		ret = drm_mm_insert_node_in_range(&mmu->mm, node,
+			etnaviv_obj->base.size, 0, mmu->last_iova, ~0UL,
+			DRM_MM_SEARCH_DEFAULT);
+
+		if (ret != -ENOSPC)
+			break;
+
+		/*
+		 * If we did not search from the start of the MMU region,
+		 * try again in case there are free slots.
+		 */
+		if (mmu->last_iova) {
+			mmu->last_iova = 0;
+			mmu->need_flush = true;
+			continue;
+		}
+
+		break;
+	}
 
 	if (!ret) {
+		mmu->last_iova = node->start + etnaviv_obj->base.size;
 		offset = node->start;
 		etnaviv_obj->iova = offset;
 		etnaviv_obj->gpu_vram_node = node;
diff --git a/drivers/staging/etnaviv/etnaviv_mmu.h b/drivers/staging/etnaviv/etnaviv_mmu.h
index 262c4e26e901..a37affda9590 100644
--- a/drivers/staging/etnaviv/etnaviv_mmu.h
+++ b/drivers/staging/etnaviv/etnaviv_mmu.h
@@ -26,6 +26,7 @@ struct etnaviv_iommu {
 
 	/* memory manager for GPU address area */
 	struct drm_mm mm;
+	uint32_t last_iova;
 	bool need_flush;
 };
 
-- 
2.1.4