[PATCH v2 6/6] bus: mhi: host: Fix runtime PM ownership between clients and controller

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

The current MHI runtime PM model allows the core to take power references
directly on the controller device without visibility into client driver
activity. As a result, a controller driver may runtime-suspend the
hardware while one or more MHI client devices are still actively in use.

This happens because the MHI core historically managed runtime PM
internally, rather than relying on standard parent-child PM dependency
tracking. The controller driver therefore has no way to infer whether MHI
clients still require the controller to remain active.

Fix this by enabling runtime PM on the MHI bus device (mhi_dev) and routing
runtime PM references through it. Client drivers now hold runtime PM
references on their own mhi_dev, allowing the PM framework to naturally
propagate activity to the controller via the device hierarchy.

The existing mhi_device_get_sync() and mhi_device_put() helpers are
retained, as they serve as the synchronization point between the MHI power
state machine and runtime PM, combining runtime PM reference management
with MHI wake handling.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/bus/mhi/host/init.c     |  3 +++
 drivers/bus/mhi/host/internal.h |  6 +++---
 drivers/bus/mhi/host/main.c     | 26 ++------------------------
 drivers/bus/mhi/host/pm.c       | 18 ++++++++----------
 4 files changed, 16 insertions(+), 37 deletions(-)

diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index 9f3ee4a14418..002f3abb8103 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -1034,6 +1034,9 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
 
 	mhi_cntrl->mhi_dev = mhi_dev;
 
+	pm_runtime_no_callbacks(&mhi_cntrl->mhi_dev->dev);
+	devm_pm_runtime_set_active_enabled(&mhi_cntrl->mhi_dev->dev);
+
 	mhi_create_debugfs(mhi_cntrl);
 
 	return 0;
diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
index a7493aabc6fa..434ed4705d25 100644
--- a/drivers/bus/mhi/host/internal.h
+++ b/drivers/bus/mhi/host/internal.h
@@ -354,9 +354,9 @@ static inline bool mhi_is_active(struct mhi_controller *mhi_cntrl)
 static inline void mhi_trigger_resume(struct mhi_controller *mhi_cntrl)
 {
 	pm_wakeup_event(&mhi_cntrl->mhi_dev->dev, 0);
-	pm_runtime_get(mhi_cntrl->cntrl_dev);
-	pm_runtime_mark_last_busy(mhi_cntrl->cntrl_dev);
-	pm_runtime_put(mhi_cntrl->cntrl_dev);
+	pm_runtime_get(&mhi_cntrl->mhi_dev->dev);
+	pm_runtime_mark_last_busy(&mhi_cntrl->mhi_dev->dev);
+	pm_runtime_put(&mhi_cntrl->mhi_dev->dev);
 }
 
 /* Register access methods */
diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index 71919c2e9462..f0b09657de29 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -658,12 +658,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
 			/* notify client */
 			mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
 
-			if (mhi_chan->dir == DMA_TO_DEVICE) {
+			if (mhi_chan->dir == DMA_TO_DEVICE)
 				atomic_dec(&mhi_cntrl->pending_pkts);
-				/* Release the reference got from mhi_queue() */
-				pm_runtime_mark_last_busy(mhi_cntrl->cntrl_dev);
-				pm_runtime_put(mhi_cntrl->cntrl_dev);
-			}
 
 			read_lock_bh(&mhi_chan->lock);
 		}
@@ -1135,12 +1131,6 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
 
 	read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
 
-	/* Packet is queued, take a usage ref to exit M3 if necessary
-	 * for host->device buffer, balanced put is done on buffer completion
-	 * for device->host buffer, balanced put is after ringing the DB
-	 */
-	pm_runtime_get(mhi_cntrl->cntrl_dev);
-
 	/* Assert dev_wake (to exit/prevent M1/M2)*/
 	mhi_cntrl->wake_toggle(mhi_cntrl);
 
@@ -1150,11 +1140,6 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
 	if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
 		mhi_ring_chan_db(mhi_cntrl, mhi_chan);
 
-	if (dir == DMA_FROM_DEVICE) {
-		pm_runtime_mark_last_busy(mhi_cntrl->cntrl_dev);
-		pm_runtime_put(mhi_cntrl->cntrl_dev);
-	}
-
 	read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
 
 	return ret;
@@ -1355,7 +1340,6 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
 	ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
 	if (ret)
 		return ret;
-	pm_runtime_get(mhi_cntrl->cntrl_dev);
 
 	reinit_completion(&mhi_chan->completion);
 	ret = mhi_send_cmd(mhi_cntrl, mhi_chan, cmd);
@@ -1386,8 +1370,6 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
 
 	trace_mhi_channel_command_end(mhi_cntrl, mhi_chan, to_state, TPS("Updated"));
 exit_channel_update:
-	pm_runtime_mark_last_busy(mhi_cntrl->cntrl_dev);
-	pm_runtime_put(mhi_cntrl->cntrl_dev);
 	mhi_device_put(mhi_cntrl->mhi_dev);
 
 	return ret;
@@ -1525,12 +1507,8 @@ static void mhi_reset_data_chan(struct mhi_controller *mhi_cntrl,
 	while (tre_ring->rp != tre_ring->wp) {
 		struct mhi_buf_info *buf_info = buf_ring->rp;
 
-		if (mhi_chan->dir == DMA_TO_DEVICE) {
+		if (mhi_chan->dir == DMA_TO_DEVICE)
 			atomic_dec(&mhi_cntrl->pending_pkts);
-			/* Release the reference got from mhi_queue() */
-			pm_runtime_mark_last_busy(mhi_cntrl->cntrl_dev);
-			pm_runtime_put(mhi_cntrl->cntrl_dev);
-		}
 
 		if (!buf_info->pre_mapped)
 			mhi_cntrl->unmap_single(mhi_cntrl, buf_info);
diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
index f799503c8f36..278fc2ffb820 100644
--- a/drivers/bus/mhi/host/pm.c
+++ b/drivers/bus/mhi/host/pm.c
@@ -429,6 +429,7 @@ static int mhi_pm_mission_mode_transition(struct mhi_controller *mhi_cntrl)
 
 	if (MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)) {
 		ret = -EIO;
+		read_unlock_bh(&mhi_cntrl->pm_lock);
 		goto error_mission_mode;
 	}
 
@@ -459,11 +460,9 @@ static int mhi_pm_mission_mode_transition(struct mhi_controller *mhi_cntrl)
 	 */
 	mhi_create_devices(mhi_cntrl);
 
-	read_lock_bh(&mhi_cntrl->pm_lock);
 
 error_mission_mode:
-	mhi_cntrl->wake_put(mhi_cntrl, false);
-	read_unlock_bh(&mhi_cntrl->pm_lock);
+	mhi_device_put(mhi_cntrl->mhi_dev);
 
 	return ret;
 }
@@ -1038,9 +1037,11 @@ int __mhi_device_get_sync(struct mhi_controller *mhi_cntrl)
 		read_unlock_bh(&mhi_cntrl->pm_lock);
 		return -EIO;
 	}
+	read_unlock_bh(&mhi_cntrl->pm_lock);
+
+	pm_runtime_get_sync(&mhi_cntrl->mhi_dev->dev);
+	read_lock_bh(&mhi_cntrl->pm_lock);
 	mhi_cntrl->wake_get(mhi_cntrl, true);
-	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
-		mhi_trigger_resume(mhi_cntrl);
 	read_unlock_bh(&mhi_cntrl->pm_lock);
 
 	ret = wait_event_timeout(mhi_cntrl->state_event,
@@ -1049,9 +1050,7 @@ int __mhi_device_get_sync(struct mhi_controller *mhi_cntrl)
 				 msecs_to_jiffies(mhi_cntrl->timeout_ms));
 
 	if (!ret || MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)) {
-		read_lock_bh(&mhi_cntrl->pm_lock);
-		mhi_cntrl->wake_put(mhi_cntrl, false);
-		read_unlock_bh(&mhi_cntrl->pm_lock);
+		mhi_device_put(mhi_cntrl->mhi_dev);
 		return -EIO;
 	}
 
@@ -1339,11 +1338,10 @@ void mhi_device_put(struct mhi_device *mhi_dev)
 
 	mhi_dev->dev_wake--;
 	read_lock_bh(&mhi_cntrl->pm_lock);
-	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
-		mhi_trigger_resume(mhi_cntrl);
 
 	mhi_cntrl->wake_put(mhi_cntrl, false);
 	read_unlock_bh(&mhi_cntrl->pm_lock);
+	pm_runtime_put(&mhi_cntrl->mhi_dev->dev);
 }
 EXPORT_SYMBOL_GPL(mhi_device_put);
 

-- 
2.34.1