drm/amdgpu: create fence slab once when amdgpu module init.

This avoids problems with multiple GPUs. For example,
if the first GPU failed before amdgpu_fence_init() was
called, amdgpu_fence_slab_ref is still 0 and it will
get decremented in amdgpu_fence_driver_fini(). This
will lead to a crash during init of the second GPU since
amdgpu_fence_slab_ref is not 0.

v2: add functions for init/exit instead of
moving the variables into the driver.

Signed-off-by: Rex Zhu <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

···
 void amdgpu_sync_free(struct amdgpu_sync *sync);
 int amdgpu_sync_init(void);
 void amdgpu_sync_fini(void);
+int amdgpu_fence_slab_init(void);
+void amdgpu_fence_slab_fini(void);
 
 /*
  * GART structures, functions & helpers

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

···
 	.driver.pm = &amdgpu_pm_ops,
 };
 
+
+
 static int __init amdgpu_init(void)
 {
 	amdgpu_sync_init();
+	amdgpu_fence_slab_init();
 	if (vgacon_text_force()) {
 		DRM_ERROR("VGACON disables amdgpu kernel modesetting.\n");
 		return -EINVAL;
···
 	driver->driver_features |= DRIVER_MODESET;
 	driver->num_ioctls = amdgpu_max_kms_ioctl;
 	amdgpu_register_atpx_handler();
-
 	/* let modprobe override vga console setting */
 	return drm_pci_init(driver, pdriver);
 }
···
 	drm_pci_exit(driver, pdriver);
 	amdgpu_unregister_atpx_handler();
 	amdgpu_sync_fini();
+	amdgpu_fence_slab_fini();
 }
 
 module_init(amdgpu_init);

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

···
 };
 
 static struct kmem_cache *amdgpu_fence_slab;
-static atomic_t amdgpu_fence_slab_ref = ATOMIC_INIT(0);
 
+int amdgpu_fence_slab_init(void)
+{
+	amdgpu_fence_slab = kmem_cache_create(
+		"amdgpu_fence", sizeof(struct amdgpu_fence), 0,
+		SLAB_HWCACHE_ALIGN, NULL);
+	if (!amdgpu_fence_slab)
+		return -ENOMEM;
+	return 0;
+}
+
+void amdgpu_fence_slab_fini(void)
+{
+	kmem_cache_destroy(amdgpu_fence_slab);
+}
 /*
  * Cast helper
  */
···
  */
 int amdgpu_fence_driver_init(struct amdgpu_device *adev)
 {
-	if (atomic_inc_return(&amdgpu_fence_slab_ref) == 1) {
-		amdgpu_fence_slab = kmem_cache_create(
-			"amdgpu_fence", sizeof(struct amdgpu_fence), 0,
-			SLAB_HWCACHE_ALIGN, NULL);
-		if (!amdgpu_fence_slab)
-			return -ENOMEM;
-	}
 	if (amdgpu_debugfs_fence_init(adev))
 		dev_err(adev->dev, "fence debugfs file creation failed\n");
 
···
 		kfree(ring->fence_drv.fences);
 		ring->fence_drv.initialized = false;
 	}
-
-	if (atomic_dec_and_test(&amdgpu_fence_slab_ref))
-		kmem_cache_destroy(amdgpu_fence_slab);
 }
 
 /**