scsi: ufs: Fix a kernel crash during shutdown

Fix the following kernel crash:

Unable to handle kernel paging request at virtual address ffffffc91e735000
Call trace:
 __queue_work+0x26c/0x624
 queue_work_on+0x6c/0xf0
 ufshcd_hold+0x12c/0x210
 __ufshcd_wl_suspend+0xc0/0x400
 ufshcd_wl_shutdown+0xb8/0xcc
 device_shutdown+0x184/0x224
 kernel_restart+0x4c/0x124
 __arm64_sys_reboot+0x194/0x264
 el0_svc_common+0xc8/0x1d4
 do_el0_svc+0x30/0x8c
 el0_svc+0x20/0x30
 el0_sync_handler+0x84/0xe4
 el0_sync+0x1bc/0x1c0

Fix this crash by ungating the clock before destroying the work queue on
which clock gating work is queued.

Link: https://lore.kernel.org/r/20211203231950.193369-15-bvanassche@acm.orgTested-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufshcd.c

@@ -1648,7 +1648,8 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
 	bool flush_result;
 	unsigned long flags;
 
-	if (!ufshcd_is_clkgating_allowed(hba))
+	if (!ufshcd_is_clkgating_allowed(hba) ||
+	    !hba->clk_gating.is_initialized)
 		goto out;
 	spin_lock_irqsave(hba->host->host_lock, flags);
 	hba->clk_gating.active_reqs++;
@@ -1808,7 +1809,7 @@ static void __ufshcd_release(struct ufs_hba *hba)
 
 	if (hba->clk_gating.active_reqs || hba->clk_gating.is_suspended ||
 	    hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL ||
-	    hba->outstanding_tasks ||
+	    hba->outstanding_tasks || !hba->clk_gating.is_initialized ||
 	    hba->active_uic_cmd || hba->uic_async_done ||
 	    hba->clk_gating.state == CLKS_OFF)
 		return;
@@ -1943,11 +1944,15 @@ static void ufshcd_exit_clk_gating(struct ufs_hba *hba)
 {
 	if (!hba->clk_gating.is_initialized)
 		return;
+
 	ufshcd_remove_clk_gating_sysfs(hba);
-	cancel_work_sync(&hba->clk_gating.ungate_work);
-	cancel_delayed_work_sync(&hba->clk_gating.gate_work);
-	destroy_workqueue(hba->clk_gating.clk_gating_workq);
+
+	/* Ungate the clock if necessary. */
+	ufshcd_hold(hba, false);
 	hba->clk_gating.is_initialized = false;
+	ufshcd_release(hba);
+
+	destroy_workqueue(hba->clk_gating.clk_gating_workq);
 }
 
 /* Must be called with host lock acquired */