drm/amdgpu: Properly allocate VM invalidate eng v2

v1: Properly allocate TLB invalidation engine to avoid conflict.
v2: Added comments to codes
Signed-off-by: Oak Zeng <Oak.Zeng@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian Konig <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c

@@ -392,7 +392,16 @@ static int gmc_v9_0_early_init(void *handle)
 static int gmc_v9_0_late_init(void *handle)
 {
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
-	unsigned vm_inv_eng[AMDGPU_MAX_VMHUBS] = { 3, 3 };
+	/*
+	 * The latest engine allocation on gfx9 is:
+	 * Engine 0, 1: idle
+	 * Engine 2, 3: firmware
+	 * Engine 4~13: amdgpu ring, subject to change when ring number changes
+	 * Engine 14~15: idle
+	 * Engine 16: kfd tlb invalidation
+	 * Engine 17: Gart flushes
+	 */
+	unsigned vm_inv_eng[AMDGPU_MAX_VMHUBS] = { 4, 4 };
 	unsigned i;
 
 	for(i = 0; i < adev->num_rings; ++i) {
@@ -405,9 +414,9 @@ static int gmc_v9_0_late_init(void *handle)
 			 ring->funcs->vmhub);
 	}
 
-	/* Engine 17 is used for GART flushes */
+	/* Engine 16 is used for KFD and 17 for GART flushes */
 	for(i = 0; i < AMDGPU_MAX_VMHUBS; ++i)
-		BUG_ON(vm_inv_eng[i] > 17);
+		BUG_ON(vm_inv_eng[i] > 16);
 
 	return amdgpu_irq_get(adev, &adev->mc.vm_fault, 0);
 }