drm/i915: Avoid using the i915_fence_array when collecting dependencies

Since the gt migration code was using only a single fence for
dependencies, these were collected in a dma_fence_array. However, it
turns out that it's illegal to use some dma_fences in a dma_fence_array,
in particular other dma_fence_arrays and dma_fence_chains, and this
causes trouble for us moving forward.

Have the gt migration code instead take a const struct i915_deps for
dependencies. This means we can skip the dma_fence_array creation
and instead pass the struct i915_deps instead to circumvent the
problem.

v2:
- Make the prev_deps() function static. (kernel test robot <lkp@intel.com>)
- Update the struct i915_deps kerneldoc.
v4:
- Rebase.

Fixes: 5652df829b3c ("drm/i915/ttm: Update i915_gem_obj_copy_ttm() to be asynchronous")
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/20211221200050.436316-2-thomas.hellstrom@linux.intel.com

2 files changed, 17 insertions, 16 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.c b/drivers/gpu/drm/i915/gt/intel_migrate.c
index 19a01878fee3..18b44af56969 100644
--- a/drivers/gpu/drm/i915/gt/intel_migrate.c
+++ b/drivers/gpu/drm/i915/gt/intel_migrate.c
@@ -404,7 +404,7 @@ static int emit_copy(struct i915_request *rq, int size)
 
 int
 intel_context_migrate_copy(struct intel_context *ce,
-			   struct dma_fence *await,
+			   const struct i915_deps *deps,
 			   struct scatterlist *src,
 			   enum i915_cache_level src_cache_level,
 			   bool src_is_lmem,
@@ -431,8 +431,8 @@ intel_context_migrate_copy(struct intel_context *ce,
 			goto out_ce;
 		}
 
-		if (await) {
-			err = i915_request_await_dma_fence(rq, await);
+		if (deps) {
+			err = i915_request_await_deps(rq, deps);
 			if (err)
 				goto out_rq;
 
@@ -442,7 +442,7 @@ intel_context_migrate_copy(struct intel_context *ce,
 					goto out_rq;
 			}
 
-			await = NULL;
+			deps = NULL;
 		}
 
 		/* The PTE updates + copy must not be interrupted. */
@@ -525,7 +525,7 @@ static int emit_clear(struct i915_request *rq, int size, u32 value)
 
 int
 intel_context_migrate_clear(struct intel_context *ce,
-			    struct dma_fence *await,
+			    const struct i915_deps *deps,
 			    struct scatterlist *sg,
 			    enum i915_cache_level cache_level,
 			    bool is_lmem,
@@ -550,8 +550,8 @@ intel_context_migrate_clear(struct intel_context *ce,
 			goto out_ce;
 		}
 
-		if (await) {
-			err = i915_request_await_dma_fence(rq, await);
+		if (deps) {
+			err = i915_request_await_deps(rq, deps);
 			if (err)
 				goto out_rq;
 
@@ -561,7 +561,7 @@ intel_context_migrate_clear(struct intel_context *ce,
 					goto out_rq;
 			}
 
-			await = NULL;
+			deps = NULL;
 		}
 
 		/* The PTE updates + clear must not be interrupted. */
@@ -599,7 +599,7 @@ out_ce:
 
 int intel_migrate_copy(struct intel_migrate *m,
 		       struct i915_gem_ww_ctx *ww,
-		       struct dma_fence *await,
+		       const struct i915_deps *deps,
 		       struct scatterlist *src,
 		       enum i915_cache_level src_cache_level,
 		       bool src_is_lmem,
@@ -624,7 +624,7 @@ int intel_migrate_copy(struct intel_migrate *m,
 	if (err)
 		goto out;
 
-	err = intel_context_migrate_copy(ce, await,
+	err = intel_context_migrate_copy(ce, deps,
 					 src, src_cache_level, src_is_lmem,
 					 dst, dst_cache_level, dst_is_lmem,
 					 out);
@@ -638,7 +638,7 @@ out:
 int
 intel_migrate_clear(struct intel_migrate *m,
 		    struct i915_gem_ww_ctx *ww,
-		    struct dma_fence *await,
+		    const struct i915_deps *deps,
 		    struct scatterlist *sg,
 		    enum i915_cache_level cache_level,
 		    bool is_lmem,
@@ -661,7 +661,7 @@ intel_migrate_clear(struct intel_migrate *m,
 	if (err)
 		goto out;
 
-	err = intel_context_migrate_clear(ce, await, sg, cache_level,
+	err = intel_context_migrate_clear(ce, deps, sg, cache_level,
 					  is_lmem, value, out);
 
 	intel_context_unpin(ce);
diff --git a/drivers/gpu/drm/i915/gt/intel_migrate.h b/drivers/gpu/drm/i915/gt/intel_migrate.h
index 4e18e755a00b..ccc677ec4aa3 100644
--- a/drivers/gpu/drm/i915/gt/intel_migrate.h
+++ b/drivers/gpu/drm/i915/gt/intel_migrate.h
@@ -11,6 +11,7 @@
 #include "intel_migrate_types.h"
 
 struct dma_fence;
+struct i915_deps;
 struct i915_request;
 struct i915_gem_ww_ctx;
 struct intel_gt;
@@ -23,7 +24,7 @@ struct intel_context *intel_migrate_create_context(struct intel_migrate *m);
 
 int intel_migrate_copy(struct intel_migrate *m,
 		       struct i915_gem_ww_ctx *ww,
-		       struct dma_fence *await,
+		       const struct i915_deps *deps,
 		       struct scatterlist *src,
 		       enum i915_cache_level src_cache_level,
 		       bool src_is_lmem,
@@ -33,7 +34,7 @@ int intel_migrate_copy(struct intel_migrate *m,
 		       struct i915_request **out);
 
 int intel_context_migrate_copy(struct intel_context *ce,
-			       struct dma_fence *await,
+			       const struct i915_deps *deps,
 			       struct scatterlist *src,
 			       enum i915_cache_level src_cache_level,
 			       bool src_is_lmem,
@@ -45,7 +46,7 @@ int intel_context_migrate_copy(struct intel_context *ce,
 int
 intel_migrate_clear(struct intel_migrate *m,
 		    struct i915_gem_ww_ctx *ww,
-		    struct dma_fence *await,
+		    const struct i915_deps *deps,
 		    struct scatterlist *sg,
 		    enum i915_cache_level cache_level,
 		    bool is_lmem,
@@ -53,7 +54,7 @@ intel_migrate_clear(struct intel_migrate *m,
 		    struct i915_request **out);
 int
 intel_context_migrate_clear(struct intel_context *ce,
-			    struct dma_fence *await,
+			    const struct i915_deps *deps,
 			    struct scatterlist *sg,
 			    enum i915_cache_level cache_level,
 			    bool is_lmem,