[PATCH v1 2/6] bus: mhi: core: Mark device inactive soon after host issues a shutdown

[Bhaumik Bhatt <bbhatt@codeaurora.org>]

Clients on the host may see the device in an active state for a short
period of time after the host detects a device error or power down.
Prevent any further host activity which could lead to race conditions
and timeouts seen by clients attempting to push data as they must be
notified of the host's intent sooner than later. This also allows the
host and device states to be in sync with one another and prevents
unnecessary host operations.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/main.c | 33 ++++++++++++++++++++++++++-------
 drivers/bus/mhi/core/pm.c   | 31 +++++++++++++++++++------------
 2 files changed, 45 insertions(+), 19 deletions(-)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index bafc12a..da32c23 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -376,6 +376,7 @@ irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *priv)
 	enum mhi_state state = MHI_STATE_MAX;
 	enum mhi_pm_state pm_state = 0;
 	enum mhi_ee_type ee = 0;
+	bool handle_rddm = false;
 
 	write_lock_irq(&mhi_cntrl->pm_lock);
 	if (!MHI_REG_ACCESS_VALID(mhi_cntrl->pm_state)) {
@@ -390,22 +391,40 @@ irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *priv)
 		TO_MHI_EXEC_STR(mhi_cntrl->ee), TO_MHI_EXEC_STR(ee),
 		TO_MHI_STATE_STR(state));
 
-	if (state == MHI_STATE_SYS_ERR) {
-		dev_dbg(dev, "System error detected\n");
-		pm_state = mhi_tryset_pm_state(mhi_cntrl,
-					       MHI_PM_SYS_ERR_DETECT);
-	}
-	write_unlock_irq(&mhi_cntrl->pm_lock);
-
 	 /* If device supports RDDM don't bother processing SYS error */
 	if (mhi_cntrl->rddm_image) {
+		/* host may be performing a device power down already */
+		if (!mhi_is_active(mhi_cntrl)) {
+			write_unlock_irq(&mhi_cntrl->pm_lock);
+			goto exit_intvec;
+		}
+
 		if (mhi_cntrl->ee == MHI_EE_RDDM && mhi_cntrl->ee != ee) {
+			/* prevent clients from queueing any more packets */
+			pm_state = mhi_tryset_pm_state(mhi_cntrl,
+						       MHI_PM_SYS_ERR_DETECT);
+			if (pm_state == MHI_PM_SYS_ERR_DETECT)
+				handle_rddm = true;
+		}
+
+		write_unlock_irq(&mhi_cntrl->pm_lock);
+
+		if (handle_rddm) {
+			dev_err(dev, "RDDM event occurred!\n");
 			mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_EE_RDDM);
 			wake_up_all(&mhi_cntrl->state_event);
 		}
 		goto exit_intvec;
 	}
 
+	if (state == MHI_STATE_SYS_ERR) {
+		dev_dbg(dev, "System error detected\n");
+		pm_state = mhi_tryset_pm_state(mhi_cntrl,
+					       MHI_PM_SYS_ERR_DETECT);
+	}
+
+	write_unlock_irq(&mhi_cntrl->pm_lock);
+
 	if (pm_state == MHI_PM_SYS_ERR_DETECT) {
 		wake_up_all(&mhi_cntrl->state_event);
 
diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
index b2b3de7..1daed86 100644
--- a/drivers/bus/mhi/core/pm.c
+++ b/drivers/bus/mhi/core/pm.c
@@ -465,15 +465,10 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
 	write_lock_irq(&mhi_cntrl->pm_lock);
 	prev_state = mhi_cntrl->pm_state;
 	cur_state = mhi_tryset_pm_state(mhi_cntrl, transition_state);
-	if (cur_state == transition_state) {
-		mhi_cntrl->ee = MHI_EE_DISABLE_TRANSITION;
+	if (cur_state == MHI_PM_SYS_ERR_PROCESS)
 		mhi_cntrl->dev_state = MHI_STATE_RESET;
-	}
 	write_unlock_irq(&mhi_cntrl->pm_lock);
 
-	/* Wake up threads waiting for state transition */
-	wake_up_all(&mhi_cntrl->state_event);
-
 	if (cur_state != transition_state) {
 		dev_err(dev, "Failed to transition to state: %s from: %s\n",
 			to_mhi_pm_state_str(transition_state),
@@ -482,6 +477,11 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
 		return;
 	}
 
+	mhi_cntrl->ee = MHI_EE_DISABLE_TRANSITION;
+
+	/* Wake up threads waiting for state transition */
+	wake_up_all(&mhi_cntrl->state_event);
+
 	/* Trigger MHI RESET so that the device will not access host memory */
 	if (MHI_REG_ACCESS_VALID(prev_state)) {
 		u32 in_reset = -1;
@@ -1048,22 +1048,29 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
 	enum dev_st_transition next_state = DEV_ST_TRANSITION_DISABLE;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
 
+	mutex_lock(&mhi_cntrl->pm_mutex);
+	write_lock_irq(&mhi_cntrl->pm_lock);
+
 	/* If it's not a graceful shutdown, force MHI to linkdown state */
 	if (!graceful) {
-		mutex_lock(&mhi_cntrl->pm_mutex);
-		write_lock_irq(&mhi_cntrl->pm_lock);
 		cur_state = mhi_tryset_pm_state(mhi_cntrl,
 						MHI_PM_LD_ERR_FATAL_DETECT);
-		write_unlock_irq(&mhi_cntrl->pm_lock);
-		mutex_unlock(&mhi_cntrl->pm_mutex);
-		if (cur_state != MHI_PM_LD_ERR_FATAL_DETECT)
+		if (cur_state != MHI_PM_LD_ERR_FATAL_DETECT) {
 			dev_dbg(dev, "Failed to move to state: %s from: %s\n",
 				to_mhi_pm_state_str(MHI_PM_LD_ERR_FATAL_DETECT),
 				to_mhi_pm_state_str(mhi_cntrl->pm_state));
-		else
+		} else {
 			next_state = DEV_ST_TRANSITION_FATAL;
+			wake_up_all(&mhi_cntrl->state_event);
+		}
 	}
 
+	/* mark device as inactive to avoid any further host processing */
+	mhi_cntrl->dev_state = MHI_STATE_RESET;
+
+	write_unlock_irq(&mhi_cntrl->pm_lock);
+	mutex_unlock(&mhi_cntrl->pm_mutex);
+
 	mhi_queue_state_transition(mhi_cntrl, next_state);
 
 	/* Wait for shutdown to complete */
-- 
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