drm/i915/selftests: test descending addresses

For igt_write_huge make sure the higher gtt offsets don't feel left out,
which is especially true when dealing with the 48b PPGTT, where we
timeout long before we are able exhaust the address space.

v2: just use IGT_TIMEOUT
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171123135421.17967-2-matthew.auld@intel.com

drivers/gpu/drm/i915/selftests/huge_pages.c

@@ -1040,6 +1040,62 @@ static int cpu_check(struct drm_i915_gem_object *obj, u32 dword, u32 val)
 	return err;
 }
 
+static int __igt_write_huge(struct i915_gem_context *ctx,
+			    struct intel_engine_cs *engine,
+			    struct drm_i915_gem_object *obj,
+			    u64 size, u64 offset,
+			    u32 dword, u32 val)
+{
+	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+	struct i915_address_space *vm = ctx->ppgtt ? &ctx->ppgtt->base : &i915->ggtt.base;
+	unsigned int flags = PIN_USER | PIN_OFFSET_FIXED;
+	struct i915_vma *vma;
+	int err;
+
+	vma = i915_vma_instance(obj, vm, NULL);
+	if (IS_ERR(vma))
+		return PTR_ERR(vma);
+
+	err = i915_vma_unbind(vma);
+	if (err)
+		goto out_vma_close;
+
+	err = i915_vma_pin(vma, size, 0, flags | offset);
+	if (err) {
+		/*
+		 * The ggtt may have some pages reserved so
+		 * refrain from erroring out.
+		 */
+		if (err == -ENOSPC && i915_is_ggtt(vm))
+			err = 0;
+
+		goto out_vma_close;
+	}
+
+	err = igt_check_page_sizes(vma);
+	if (err)
+		goto out_vma_unpin;
+
+	err = gpu_write(vma, ctx, engine, dword, val);
+	if (err) {
+		pr_err("gpu-write failed at offset=%llx\n", offset);
+		goto out_vma_unpin;
+	}
+
+	err = cpu_check(obj, dword, val);
+	if (err) {
+		pr_err("cpu-check failed at offset=%llx\n", offset);
+		goto out_vma_unpin;
+	}
+
+out_vma_unpin:
+	i915_vma_unpin(vma);
+out_vma_close:
+	i915_vma_close(vma);
+
+	return err;
+}
+
 static int igt_write_huge(struct i915_gem_context *ctx,
 			  struct drm_i915_gem_object *obj)
 {
@@ -1049,8 +1105,6 @@ static int igt_write_huge(struct i915_gem_context *ctx,
 	struct intel_engine_cs *engine;
 	I915_RND_STATE(prng);
 	IGT_TIMEOUT(end_time);
-	struct i915_vma *vma;
-	unsigned int flags = PIN_USER | PIN_OFFSET_FIXED;
 	unsigned int max_page_size;
 	unsigned int id;
 	u64 max;
@@ -1069,10 +1123,6 @@ static int igt_write_huge(struct i915_gem_context *ctx,
 	max_page_size = rounddown_pow_of_two(obj->mm.page_sizes.sg);
 	max = div_u64((vm->total - size), max_page_size);
 
-	vma = i915_vma_instance(obj, vm, NULL);
-	if (IS_ERR(vma))
-		return PTR_ERR(vma);
-
 	n = 0;
 	for_each_engine(engine, i915, id) {
 		if (!intel_engine_can_store_dword(engine)) {
@@ -1095,66 +1145,33 @@ static int igt_write_huge(struct i915_gem_context *ctx,
 		return -ENOMEM;
 
 	/*
-	 * Try various offsets until we timeout -- we want to avoid
-	 * issues hidden by effectively always using offset = 0.
+	 * Try various offsets in an ascending/descending fashion until we
+	 * timeout -- we want to avoid issues hidden by effectively always using
+	 * offset = 0.
 	 */
 	i = 0;
 	for_each_prime_number_from(num, 0, max) {
-		u64 offset = num * max_page_size;
-		u32 dword;
-
-		err = i915_vma_unbind(vma);
-		if (err)
-			goto out_vma_close;
-
-		err = i915_vma_pin(vma, size, max_page_size, flags | offset);
-		if (err) {
-			/*
-			 * The ggtt may have some pages reserved so
-			 * refrain from erroring out.
-			 */
-			if (err == -ENOSPC && i915_is_ggtt(vm)) {
-				err = 0;
-				continue;
-			}
-
-			goto out_vma_close;
-		}
-
-		err = igt_check_page_sizes(vma);
-		if (err)
-			goto out_vma_unpin;
-
-		dword = offset_in_page(num) / 4;
+		u64 offset_low = num * max_page_size;
+		u64 offset_high = (max - num) * max_page_size;
+		u32 dword = offset_in_page(num) / 4;
 
 		engine = engines[order[i] % n];
 		i = (i + 1) % (n * I915_NUM_ENGINES);
 
-		err = gpu_write(vma, ctx, engine, dword, num + 1);
-		if (err) {
-			pr_err("gpu-write failed at offset=%llx", offset);
-			goto out_vma_unpin;
-		}
-
-		err = cpu_check(obj, dword, num + 1);
-		if (err) {
-			pr_err("cpu-check failed at offset=%llx", offset);
-			goto out_vma_unpin;
-		}
+		err = __igt_write_huge(ctx, engine, obj, size, offset_low, dword, num + 1);
+		if (err)
+			break;
 
-		i915_vma_unpin(vma);
+		err = __igt_write_huge(ctx, engine, obj, size, offset_high, dword, num + 1);
+		if (err)
+			break;
 
 		if (igt_timeout(end_time,
-				"%s timed out on engine=%u at offset=%llx, max_page_size=%x\n",
-				__func__, engine->id, offset, max_page_size))
+				"%s timed out on engine=%u, offset_low=%llx offset_high=%llx, max_page_size=%x\n",
+				__func__, engine->id, offset_low, offset_high, max_page_size))
 			break;
 	}
 
-out_vma_unpin:
-	if (i915_vma_is_pinned(vma))
-		i915_vma_unpin(vma);
-out_vma_close:
-	i915_vma_close(vma);
 	kfree(order);
 
 	return err;