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

[Lucas Stach]

From: Russell King <rmk+ker...@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