patch "bus: mhi: ep: Change state_lock to mutex" added to char-misc-testing

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    bus: mhi: ep: Change state_lock to mutex

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


From 1ddc7618294084fff8d673217a9479550990ee84 Mon Sep 17 00:00:00 2001
From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Date: Mon, 23 Jan 2023 12:59:45 +0530
Subject: bus: mhi: ep: Change state_lock to mutex

state_lock, the spinlock type is meant to protect race against concurrent
MHI state transitions. In mhi_ep_set_m0_state(), while the state_lock is
being held, the channels are resumed in mhi_ep_resume_channels() if the
previous state was M3. This causes sleeping in atomic bug, since
mhi_ep_resume_channels() use mutex internally.

Since the state_lock is supposed to be held throughout the state change,
it is not ideal to drop the lock before calling mhi_ep_resume_channels().
So to fix this issue, let's change the type of state_lock to mutex. This
would also allow holding the lock throughout all state transitions thereby
avoiding any potential race.

Cc: <stable@vger.kernel.org> # 5.19
Fixes: e4b7b5f0f30a ("bus: mhi: ep: Add support for suspending and resuming channels")
Reported-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/bus/mhi/ep/main.c |  8 +++++---
 drivers/bus/mhi/ep/sm.c   | 42 ++++++++++++++++++++++-----------------
 include/linux/mhi_ep.h    |  4 ++--
 3 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index bcaaba97ef63..528c00b232bf 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -1001,11 +1001,11 @@ static void mhi_ep_reset_worker(struct work_struct *work)
 
 	mhi_ep_power_down(mhi_cntrl);
 
-	spin_lock_bh(&mhi_cntrl->state_lock);
+	mutex_lock(&mhi_cntrl->state_lock);
+
 	/* Reset MMIO to signal host that the MHI_RESET is completed in endpoint */
 	mhi_ep_mmio_reset(mhi_cntrl);
 	cur_state = mhi_cntrl->mhi_state;
-	spin_unlock_bh(&mhi_cntrl->state_lock);
 
 	/*
 	 * Only proceed further if the reset is due to SYS_ERR. The host will
@@ -1014,6 +1014,8 @@ static void mhi_ep_reset_worker(struct work_struct *work)
 	 */
 	if (cur_state == MHI_STATE_SYS_ERR)
 		mhi_ep_power_up(mhi_cntrl);
+
+	mutex_unlock(&mhi_cntrl->state_lock);
 }
 
 /*
@@ -1386,8 +1388,8 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
 
 	INIT_LIST_HEAD(&mhi_cntrl->st_transition_list);
 	INIT_LIST_HEAD(&mhi_cntrl->ch_db_list);
-	spin_lock_init(&mhi_cntrl->state_lock);
 	spin_lock_init(&mhi_cntrl->list_lock);
+	mutex_init(&mhi_cntrl->state_lock);
 	mutex_init(&mhi_cntrl->event_lock);
 
 	/* Set MHI version and AMSS EE before enumeration */
diff --git a/drivers/bus/mhi/ep/sm.c b/drivers/bus/mhi/ep/sm.c
index 3655c19e23c7..fd200b2ac0bb 100644
--- a/drivers/bus/mhi/ep/sm.c
+++ b/drivers/bus/mhi/ep/sm.c
@@ -63,24 +63,23 @@ int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl)
 	int ret;
 
 	/* If MHI is in M3, resume suspended channels */
-	spin_lock_bh(&mhi_cntrl->state_lock);
+	mutex_lock(&mhi_cntrl->state_lock);
+
 	old_state = mhi_cntrl->mhi_state;
 	if (old_state == MHI_STATE_M3)
 		mhi_ep_resume_channels(mhi_cntrl);
 
 	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M0);
-	spin_unlock_bh(&mhi_cntrl->state_lock);
-
 	if (ret) {
 		mhi_ep_handle_syserr(mhi_cntrl);
-		return ret;
+		goto err_unlock;
 	}
 
 	/* Signal host that the device moved to M0 */
 	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_M0);
 	if (ret) {
 		dev_err(dev, "Failed sending M0 state change event\n");
-		return ret;
+		goto err_unlock;
 	}
 
 	if (old_state == MHI_STATE_READY) {
@@ -88,11 +87,14 @@ int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl)
 		ret = mhi_ep_send_ee_event(mhi_cntrl, MHI_EE_AMSS);
 		if (ret) {
 			dev_err(dev, "Failed sending AMSS EE event\n");
-			return ret;
+			goto err_unlock;
 		}
 	}
 
-	return 0;
+err_unlock:
+	mutex_unlock(&mhi_cntrl->state_lock);
+
+	return ret;
 }
 
 int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl)
@@ -100,13 +102,12 @@ int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl)
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
 	int ret;
 
-	spin_lock_bh(&mhi_cntrl->state_lock);
-	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M3);
-	spin_unlock_bh(&mhi_cntrl->state_lock);
+	mutex_lock(&mhi_cntrl->state_lock);
 
+	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M3);
 	if (ret) {
 		mhi_ep_handle_syserr(mhi_cntrl);
-		return ret;
+		goto err_unlock;
 	}
 
 	mhi_ep_suspend_channels(mhi_cntrl);
@@ -115,10 +116,13 @@ int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl)
 	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_M3);
 	if (ret) {
 		dev_err(dev, "Failed sending M3 state change event\n");
-		return ret;
+		goto err_unlock;
 	}
 
-	return 0;
+err_unlock:
+	mutex_unlock(&mhi_cntrl->state_lock);
+
+	return ret;
 }
 
 int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl)
@@ -127,22 +131,24 @@ int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl)
 	enum mhi_state mhi_state;
 	int ret, is_ready;
 
-	spin_lock_bh(&mhi_cntrl->state_lock);
+	mutex_lock(&mhi_cntrl->state_lock);
+
 	/* Ensure that the MHISTATUS is set to RESET by host */
 	mhi_state = mhi_ep_mmio_masked_read(mhi_cntrl, EP_MHISTATUS, MHISTATUS_MHISTATE_MASK);
 	is_ready = mhi_ep_mmio_masked_read(mhi_cntrl, EP_MHISTATUS, MHISTATUS_READY_MASK);
 
 	if (mhi_state != MHI_STATE_RESET || is_ready) {
 		dev_err(dev, "READY state transition failed. MHI host not in RESET state\n");
-		spin_unlock_bh(&mhi_cntrl->state_lock);
-		return -EIO;
+		ret = -EIO;
+		goto err_unlock;
 	}
 
 	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_READY);
-	spin_unlock_bh(&mhi_cntrl->state_lock);
-
 	if (ret)
 		mhi_ep_handle_syserr(mhi_cntrl);
 
+err_unlock:
+	mutex_unlock(&mhi_cntrl->state_lock);
+
 	return ret;
 }
diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
index 478aece17046..f198a8ac7ee7 100644
--- a/include/linux/mhi_ep.h
+++ b/include/linux/mhi_ep.h
@@ -70,8 +70,8 @@ struct mhi_ep_db_info {
  * @cmd_ctx_cache_phys: Physical address of the host command context cache
  * @chdb: Array of channel doorbell interrupt info
  * @event_lock: Lock for protecting event rings
- * @list_lock: Lock for protecting state transition and channel doorbell lists
  * @state_lock: Lock for protecting state transitions
+ * @list_lock: Lock for protecting state transition and channel doorbell lists
  * @st_transition_list: List of state transitions
  * @ch_db_list: List of queued channel doorbells
  * @wq: Dedicated workqueue for handling rings and state changes
@@ -117,8 +117,8 @@ struct mhi_ep_cntrl {
 
 	struct mhi_ep_db_info chdb[4];
 	struct mutex event_lock;
+	struct mutex state_lock;
 	spinlock_t list_lock;
-	spinlock_t state_lock;
 
 	struct list_head st_transition_list;
 	struct list_head ch_db_list;
-- 
2.39.1