bus: mhi: core: Handle disable transitions in state worker

Mission mode transition is handled by state worker thread but
power off is not. There is a possibility while mission mode
transition is in progress which calls MHI client driver probe,
power off is issued by MHI controller. This results into client
driver probe and remove running in parallel and causes use after
free situation. By queuing disable transition work when mission
mode is in progress prevents the race condition.

Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20200521170249.21795-11-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/bus/mhi/core/init.c

@@ -35,6 +35,7 @@ const char * const dev_state_tran_str[DEV_ST_TRANSITION_MAX] = {
 	[DEV_ST_TRANSITION_SBL] = "SBL",
 	[DEV_ST_TRANSITION_MISSION_MODE] = "MISSION_MODE",
 	[DEV_ST_TRANSITION_SYS_ERR] = "SYS_ERR",
+	[DEV_ST_TRANSITION_DISABLE] = "DISABLE",
 };
 
 const char * const mhi_state_str[MHI_STATE_MAX] = {

drivers/bus/mhi/core/internal.h

@@ -387,6 +387,7 @@ enum dev_st_transition {
 	DEV_ST_TRANSITION_SBL,
 	DEV_ST_TRANSITION_MISSION_MODE,
 	DEV_ST_TRANSITION_SYS_ERR,
+	DEV_ST_TRANSITION_DISABLE,
 	DEV_ST_TRANSITION_MAX,
 };
 

drivers/bus/mhi/core/pm.c

@@ -657,6 +657,10 @@ void mhi_pm_st_worker(struct work_struct *work)
 			mhi_pm_disable_transition
 				(mhi_cntrl, MHI_PM_SYS_ERR_PROCESS);
 			break;
+		case DEV_ST_TRANSITION_DISABLE:
+			mhi_pm_disable_transition
+				(mhi_cntrl, MHI_PM_SHUTDOWN_PROCESS);
+			break;
 		default:
 			break;
 		}
@@ -1011,7 +1015,12 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
 				to_mhi_pm_state_str(MHI_PM_LD_ERR_FATAL_DETECT),
 				to_mhi_pm_state_str(mhi_cntrl->pm_state));
 	}
-	mhi_pm_disable_transition(mhi_cntrl, MHI_PM_SHUTDOWN_PROCESS);
+
+	mhi_queue_state_transition(mhi_cntrl, DEV_ST_TRANSITION_DISABLE);
+
+	/* Wait for shutdown to complete */
+	flush_work(&mhi_cntrl->st_worker);
+
 	mhi_deinit_free_irq(mhi_cntrl);
 
 	if (!mhi_cntrl->pre_init) {