[RFT v2] iommu/amd: use subsys_initcall() on amdv2 iommu

["Luis R. Rodriguez" <mcgrof@kernel.org>]

We need to ensure amd iommu v2 initializes before
driver uses such as drivers/gpu/drm/amd/amdkfd/kfd_module.c,
to do this make its init routine a subsys_initcall() which
ensures its load init is called first than modules when
built-in.

This reverts the old work around implemented through commit
1bacc894c227fad8a7 ("drivers: Move iommu/ before gpu/ in Makefile"),
instead of making the dependency implicit by linker order this
makes the ordering requirement explicit through proper kernel
APIs.

Cc: Oded Gabbay <oded.gabbay@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---

This goes along with the revert included. Can someone please test?

 drivers/Makefile             | 6 ++----
 drivers/iommu/amd_iommu_v2.c | 2 +-
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/Makefile b/drivers/Makefile
index 8f5d076baeb0..cc3cfbddc376 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -50,10 +50,7 @@ obj-$(CONFIG_RESET_CONTROLLER)	+= reset/
 obj-y				+= tty/
 obj-y				+= char/
 
-# iommu/ comes before gpu as gpu are using iommu controllers
-obj-$(CONFIG_IOMMU_SUPPORT)	+= iommu/
-
-# gpu/ comes after char for AGP vs DRM startup and after iommu
+# gpu/ comes after char for AGP vs DRM startup
 obj-y				+= gpu/
 
 obj-$(CONFIG_CONNECTOR)		+= connector/
@@ -146,6 +143,7 @@ obj-y				+= clk/
 
 obj-$(CONFIG_MAILBOX)		+= mailbox/
 obj-$(CONFIG_HWSPINLOCK)	+= hwspinlock/
+obj-$(CONFIG_IOMMU_SUPPORT)	+= iommu/
 obj-$(CONFIG_REMOTEPROC)	+= remoteproc/
 obj-$(CONFIG_RPMSG)		+= rpmsg/
 
diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 56999d2fac07..60df645b9927 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -1004,5 +1004,5 @@ static void __exit amd_iommu_v2_exit(void)
 	destroy_workqueue(iommu_wq);
 }
 
-module_init(amd_iommu_v2_init);
+subsys_initcall(amd_iommu_v2_init);
 module_exit(amd_iommu_v2_exit);
-- 
2.7.2