drm/i915/ttm: Drop region reference counting

There is an interesting refcounting loop:
struct intel_memory_region has a struct ttm_resource_manager,
ttm_resource_manager->move may hold a reference to i915_request,
i915_request may hold a reference to intel_context,
intel_context may hold a reference to drm_i915_gem_object,
drm_i915_gem_object may hold a reference to intel_memory_region.

Break this loop by dropping region reference counting.

In addition, Have regions with a manager moving fence make sure
that all region objects are released before freeing the region.

v6:
- Fix a code comment.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211122214554.371864-4-thomas.hellstrom@linux.intel.com

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
index aec838ecb2ef..9ea49e0a27c0 100644
--- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
+++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
@@ -66,12 +66,16 @@ static void release_fake_lmem_bar(struct intel_memory_region *mem)
 			   DMA_ATTR_FORCE_CONTIGUOUS);
 }
 
-static void
+static int
 region_lmem_release(struct intel_memory_region *mem)
 {
-	intel_region_ttm_fini(mem);
+	int ret;
+
+	ret = intel_region_ttm_fini(mem);
 	io_mapping_fini(&mem->iomap);
 	release_fake_lmem_bar(mem);
+
+	return ret;
 }
 
 static int
@@ -231,7 +235,7 @@ static struct intel_memory_region *setup_lmem(struct intel_gt *gt)
 	return mem;
 
 err_region_put:
-	intel_memory_region_put(mem);
+	intel_memory_region_destroy(mem);
 	return ERR_PTR(err);
 }