drm/amdgpu: no need to clean debugfs at amdgpu

drm_minor_unregister will invoke drm_debugfs_cleanup
to clean all the child node under primary minor node.
We don't need to invoke amdgpu_debugfs_fini and
amdgpu_debugfs_regs_cleanup to clean agian.
Otherwise, it will raise the NULL pointer like below.
[   45.046029] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8
[   45.047256] PGD 0 P4D 0
[   45.047713] Oops: 0002 [#1] SMP PTI
[   45.048198] CPU: 0 PID: 2796 Comm: modprobe Tainted: G        W  OE     4.18.0-15-generic #16~18.04.1-Ubuntu
[   45.049538] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
[   45.050651] RIP: 0010:down_write+0x1f/0x40
[   45.051194] Code: 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 53 48 89 fb e8 ce d9 ff ff 48 ba 01 00 00 00 ff ff ff ff 48 89 d8 <f0> 48 0f c1 10 85 d2 74 05 e8 53 1c ff ff 65 48 8b 04 25 00 5c 01
[   45.053702] RSP: 0018:ffffad8f4133fd40 EFLAGS: 00010246
[   45.054384] RAX: 00000000000000a8 RBX: 00000000000000a8 RCX: ffffa011327dd814
[   45.055349] RDX: ffffffff00000001 RSI: 0000000000000001 RDI: 00000000000000a8
[   45.056346] RBP: ffffad8f4133fd48 R08: 0000000000000000 R09: ffffffffc0690a00
[   45.057326] R10: ffffad8f4133fd58 R11: 0000000000000001 R12: ffffa0113cff0300
[   45.058266] R13: ffffa0113c0a0000 R14: ffffffffc0c02a10 R15: ffffa0113e5c7860
[   45.059221] FS:  00007f60d46f9540(0000) GS:ffffa0113fc00000(0000) knlGS:0000000000000000
[   45.060809] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   45.061826] CR2: 00000000000000a8 CR3: 0000000136250004 CR4: 00000000003606f0
[   45.062913] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   45.064404] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   45.065897] Call Trace:
[   45.066426]  debugfs_remove+0x36/0xa0
[   45.067131]  amdgpu_debugfs_ring_fini+0x15/0x20 [amdgpu]
[   45.068019]  amdgpu_debugfs_fini+0x2c/0x50 [amdgpu]
[   45.068756]  amdgpu_pci_remove+0x49/0x70 [amdgpu]
[   45.069439]  pci_device_remove+0x3e/0xc0
[   45.070037]  device_release_driver_internal+0x18a/0x260
[   45.070842]  driver_detach+0x3f/0x80
[   45.071325]  bus_remove_driver+0x59/0xd0
[   45.071850]  driver_unregister+0x2c/0x40
[   45.072377]  pci_unregister_driver+0x22/0xa0
[   45.073043]  amdgpu_exit+0x15/0x57c [amdgpu]
[   45.073683]  __x64_sys_delete_module+0x146/0x280
[   45.074369]  do_syscall_64+0x5a/0x120
[   45.074916]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

v2: remove all debugfs cleanup/fini code at amdgpu
v3: squash in unused variable removal
Signed-off-by: Yintian Tao <yttao@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -992,18 +992,6 @@ int amdgpu_debugfs_regs_init(struct amdgpu_device *adev)
 	return 0;
 }
 
-void amdgpu_debugfs_regs_cleanup(struct amdgpu_device *adev)
-{
-	unsigned i;
-
-	for (i = 0; i < ARRAY_SIZE(debugfs_regs); i++) {
-		if (adev->debugfs_regs[i]) {
-			debugfs_remove(adev->debugfs_regs[i]);
-			adev->debugfs_regs[i] = NULL;
-		}
-	}
-}
-
 static int amdgpu_debugfs_test_ib(struct seq_file *m, void *data)
 {
 	struct drm_info_node *node = (struct drm_info_node *) m->private;
@@ -1339,31 +1327,13 @@ int amdgpu_debugfs_init(struct amdgpu_device *adev)
 					ARRAY_SIZE(amdgpu_debugfs_list));
 }
 
-void amdgpu_debugfs_fini(struct amdgpu_device *adev)
-{
-	int i;
-
-	for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
-		struct amdgpu_ring *ring = adev->rings[i];
-
-		if (!ring)
-			continue;
-
-		amdgpu_debugfs_ring_fini(ring);
-	}
-	amdgpu_ttm_debugfs_fini(adev);
-	debugfs_remove(adev->debugfs_preempt);
-}
-
 #else
 int amdgpu_debugfs_init(struct amdgpu_device *adev)
 {
 	return 0;
 }
-void amdgpu_debugfs_fini(struct amdgpu_device *adev) { }
 int amdgpu_debugfs_regs_init(struct amdgpu_device *adev)
 {
 	return 0;
 }
-void amdgpu_debugfs_regs_cleanup(struct amdgpu_device *adev) { }
 #endif

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

@@ -32,7 +32,6 @@ struct amdgpu_debugfs {
 };
 
 int amdgpu_debugfs_regs_init(struct amdgpu_device *adev);
-void amdgpu_debugfs_regs_cleanup(struct amdgpu_device *adev);
 int amdgpu_debugfs_init(struct amdgpu_device *adev);
 void amdgpu_debugfs_fini(struct amdgpu_device *adev);
 int amdgpu_debugfs_add_files(struct amdgpu_device *adev,

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

@@ -3235,7 +3235,6 @@ void amdgpu_device_fini(struct amdgpu_device *adev)
 	adev->rmmio = NULL;
 	amdgpu_device_doorbell_fini(adev);
 
-	amdgpu_debugfs_regs_cleanup(adev);
 	device_remove_file(adev->dev, &dev_attr_pcie_replay_count);
 	if (adev->ucode_sysfs_en)
 		amdgpu_ucode_sysfs_fini(adev);

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

@@ -1121,7 +1121,6 @@ static void
 amdgpu_pci_remove(struct pci_dev *pdev)
 {
 	struct drm_device *dev = pci_get_drvdata(pdev);
-	struct amdgpu_device *adev = dev->dev_private;
 
 #ifdef MODULE
 	if (THIS_MODULE->state != MODULE_STATE_GOING)
@@ -1129,7 +1128,6 @@ amdgpu_pci_remove(struct pci_dev *pdev)
 		DRM_ERROR("Hotplug removal is not supported\n");
 	drm_dev_unplug(dev);
 	drm_dev_put(dev);
-	amdgpu_debugfs_fini(adev);
 	amdgpu_driver_unload_kms(dev);
 	pci_disable_device(pdev);
 	pci_set_drvdata(pdev, NULL);

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

@@ -499,13 +499,6 @@ int amdgpu_debugfs_ring_init(struct amdgpu_device *adev,
 	return 0;
 }
 
-void amdgpu_debugfs_ring_fini(struct amdgpu_ring *ring)
-{
-#if defined(CONFIG_DEBUG_FS)
-	debugfs_remove(ring->ent);
-#endif
-}
-
 /**
  * amdgpu_ring_test_helper - tests ring and set sched readiness status
  *

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

@@ -2565,13 +2565,3 @@ int amdgpu_ttm_debugfs_init(struct amdgpu_device *adev)
 	return 0;
 #endif
 }
-
-void amdgpu_ttm_debugfs_fini(struct amdgpu_device *adev)
-{
-#if defined(CONFIG_DEBUG_FS)
-	unsigned i;
-
-	for (i = 0; i < ARRAY_SIZE(ttm_debugfs_entries); i++)
-		debugfs_remove(adev->mman.debugfs_entries[i]);
-#endif
-}

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

@@ -134,6 +134,5 @@ uint64_t amdgpu_ttm_tt_pte_flags(struct amdgpu_device *adev, struct ttm_tt *ttm,
 				 struct ttm_mem_reg *mem);
 
 int amdgpu_ttm_debugfs_init(struct amdgpu_device *adev);
-void amdgpu_ttm_debugfs_fini(struct amdgpu_device *adev);
 
 #endif