soc: qcom: smsm: fix of_node refcnting problem

of_find_node_with_property() drops the reference to the 'from' node,
which eventually (after enough -EPROBE_DEFERs) drops the last reference
to the node causing all sorts of fun problems, and this nice splat.

  BUG: sleeping function called from invalid context at ../kernel/locking/mutex.c:747
  in_atomic(): 1, irqs_disabled(): 128, pid: 33, name: kworker/0:1
  4 locks held by kworker/0:1/33:
   #0:  ("events"){.+.+.+}, at: [<ffff0000080fa91c>] process_one_work+0x1a4/0x728
   #1:  (deferred_probe_work){+.+.+.}, at: [<ffff0000080fa91c>] process_one_work+0x1a4/0x728
   #2:  (&dev->mutex){......}, at: [<ffff000008676078>] __device_attach+0x30/0x168
   #3:  (devtree_lock){......}, at: [<ffff000008828fd0>] of_find_node_with_property+0x30/0xe0
  irq event stamp: 18976
  hardirqs last  enabled at (18975): [<ffff00000815794c>] __down_trylock_console_sem+0x74/0xb8
  hardirqs last disabled at (18976): [<ffff0000089e26d4>] _raw_spin_lock_irqsave+0x2c/0x78
  softirqs last  enabled at (16880): [<ffff0000080e0f00>] __do_softirq+0x580/0x640
  softirqs last disabled at (16871): [<ffff0000080e13a4>] irq_exit+0xe4/0x138
  CPU: 0 PID: 33 Comm: kworker/0:1 Tainted: G            E   4.12.0-rc5+ #1455
  Hardware name: qualcomm dragonboard410c/dragonboard410c, BIOS 2017.07-rc1-00234-g22fa70a-dirty 06/26/2017
  Workqueue: events deferred_probe_work_func
  Call trace:
  [<ffff000008089ee0>] dump_backtrace+0x0/0x230
  [<ffff00000808a134>] show_stack+0x24/0x30
  [<ffff0000084e1944>] dump_stack+0xac/0xe8
  [<ffff00000810d7e0>] ___might_sleep+0x150/0x230
  [<ffff00000810d918>] __might_sleep+0x58/0x90
  [<ffff0000089dde18>] __mutex_lock+0x50/0x870
  [<ffff0000089de674>] mutex_lock_nested+0x3c/0x50
  [<ffff000008388ae0>] kernfs_remove+0x30/0x50
  [<ffff00000838b720>] sysfs_remove_dir+0x58/0x70
  [<ffff0000084e393c>] kobject_del+0x1c/0x58
  [<ffff0000084e374c>] kobject_put+0xb4/0x208
  [<ffff00000882c364>] of_node_put+0x24/0x30
  [<ffff000008829018>] of_find_node_with_property+0x78/0xe0
  [<ffff000000aff5f4>] qcom_smsm_probe+0x194/0x720 [smsm]
  [<ffff0000086793b4>] platform_drv_probe+0x74/0x110
  [<ffff0000086765bc>] driver_probe_device+0x2b4/0x420
  [<ffff000008676920>] __device_attach_driver+0xd0/0x150
  [<ffff000008673e78>] bus_for_each_drv+0x68/0xa8
  [<ffff00000867611c>] __device_attach+0xd4/0x168
  [<ffff000008676a1c>] device_initial_probe+0x24/0x30
  [<ffff000008675380>] bus_probe_device+0xa0/0xa8
  [<ffff000008675948>] deferred_probe_work_func+0xb8/0xf8
  [<ffff0000080fa9d4>] process_one_work+0x25c/0x728
  [<ffff0000080faef4>] worker_thread+0x54/0x3d8
  [<ffff0000081031d8>] kthread+0x110/0x140
  [<ffff000008082d90>] ret_from_fork+0x10/0x40
  OF: ERROR: Bad of_node_put() on /smsm
  CPU: 0 PID: 33 Comm: kworker/0:1 Tainted: G        W   E   4.12.0-rc5+ #1455
  Hardware name: qualcomm dragonboard410c/dragonboard410c, BIOS 2017.07-rc1-00234-g22fa70a-dirty 06/26/2017
  Workqueue: events deferred_probe_work_func
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

drivers/soc/qcom/smsm.c

@@ -496,7 +496,8 @@ static int qcom_smsm_probe(struct platform_device *pdev)
 	if (!smsm->hosts)
 		return -ENOMEM;
 
-	local_node = of_find_node_with_property(pdev->dev.of_node, "#qcom,smem-state-cells");
+	local_node = of_find_node_with_property(of_node_get(pdev->dev.of_node),
+						"#qcom,smem-state-cells");
 	if (!local_node) {
 		dev_err(&pdev->dev, "no state entry\n");
 		return -EINVAL;