scsi: ufs: core: Start the RTC update work later

The RTC update work involves runtime resuming the UFS controller. Hence,
only start the RTC update work after runtime power management in the UFS
driver has been fully initialized. This patch fixes the following kernel
crash:

Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Workqueue: events ufshcd_rtc_work
Call trace:
 _raw_spin_lock_irqsave+0x34/0x8c (P)
 pm_runtime_get_if_active+0x24/0x9c (L)
 pm_runtime_get_if_active+0x24/0x9c
 ufshcd_rtc_work+0x138/0x1b4
 process_one_work+0x148/0x288
 worker_thread+0x2cc/0x3d4
 kthread+0x110/0x114
 ret_from_fork+0x10/0x20

Reported-by: Neil Armstrong <[email protected]>
Closes: https://lore.kernel.org/linux-scsi/[email protected]/
Fixes: 6bf999e ("scsi: ufs: core: Add UFS RTC support")
Cc: Bean Huo <[email protected]>
Cc: [email protected]
Signed-off-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Peter Wang <[email protected]>
Reviewed-by: Bean Huo <[email protected]>
Tested-by: Neil Armstrong <[email protected]> # on SM8650-HDK
Signed-off-by: Martin K. Petersen <[email protected]>

drivers/ufs/core/ufshcd.c

@@ -8636,6 +8636,14 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
 		ufshcd_init_clk_scaling_sysfs(hba);
 	}
 
+	/*
+	 * The RTC update code accesses the hba->ufs_device_wlun->sdev_gendev
+	 * pointer and hence must only be started after the WLUN pointer has
+	 * been initialized by ufshcd_scsi_add_wlus().
+	 */
+	schedule_delayed_work(&hba->ufs_rtc_update_work,
+			      msecs_to_jiffies(UFS_RTC_UPDATE_INTERVAL_MS));
+
 	ufs_bsg_probe(hba);
 	scsi_scan_host(hba->host);
 
@@ -8795,8 +8803,6 @@ static int ufshcd_device_init(struct ufs_hba *hba, bool init_dev_params)
 	ufshcd_force_reset_auto_bkops(hba);
 
 	ufshcd_set_timestamp_attr(hba);
-	schedule_delayed_work(&hba->ufs_rtc_update_work,
-			      msecs_to_jiffies(UFS_RTC_UPDATE_INTERVAL_MS));
 
 	/* Gear up to HS gear if supported */
 	if (hba->max_pwr_info.is_valid) {