[PATCH v4 02/12] bus: mhi: core: Move to using high priority workqueue

[Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>]

MHI work is currently scheduled on the global/system workqueue and can
encounter delays on a stressed system. To avoid those unforeseen
delays which can hamper bootup or shutdown times, use a dedicated high
priority workqueue instead of the global/system workqueue.

Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
---
 drivers/bus/mhi/core/init.c | 9 +++++++++
 drivers/bus/mhi/core/pm.c   | 2 +-
 include/linux/mhi.h         | 2 ++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 8cefa35..877e40c 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -880,6 +880,13 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
 	INIT_WORK(&mhi_cntrl->st_worker, mhi_pm_st_worker);
 	init_waitqueue_head(&mhi_cntrl->state_event);
 
+	mhi_cntrl->hiprio_wq = alloc_ordered_workqueue
+				("mhi_hiprio_wq", WQ_MEM_RECLAIM | WQ_HIGHPRI);
+	if (!mhi_cntrl->hiprio_wq) {
+		dev_err(mhi_cntrl->cntrl_dev, "Failed to allocate workqueue\n");
+		goto error_alloc_cmd;
+	}
+
 	mhi_cmd = mhi_cntrl->mhi_cmd;
 	for (i = 0; i < NR_OF_CMD_RINGS; i++, mhi_cmd++)
 		spin_lock_init(&mhi_cmd->lock);
@@ -969,6 +976,7 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
 error_alloc_cmd:
 	vfree(mhi_cntrl->mhi_chan);
 	kfree(mhi_cntrl->mhi_event);
+	destroy_workqueue(mhi_cntrl->hiprio_wq);
 
 	return ret;
 }
@@ -982,6 +990,7 @@ void mhi_unregister_controller(struct mhi_controller *mhi_cntrl)
 
 	mhi_destroy_debugfs(mhi_cntrl);
 
+	destroy_workqueue(mhi_cntrl->hiprio_wq);
 	kfree(mhi_cntrl->mhi_cmd);
 	kfree(mhi_cntrl->mhi_event);
 
diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
index 3de7b16..805b6fa74 100644
--- a/drivers/bus/mhi/core/pm.c
+++ b/drivers/bus/mhi/core/pm.c
@@ -597,7 +597,7 @@ int mhi_queue_state_transition(struct mhi_controller *mhi_cntrl,
 	list_add_tail(&item->node, &mhi_cntrl->transition_list);
 	spin_unlock_irqrestore(&mhi_cntrl->transition_lock, flags);
 
-	schedule_work(&mhi_cntrl->st_worker);
+	queue_work(mhi_cntrl->hiprio_wq, &mhi_cntrl->st_worker);
 
 	return 0;
 }
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index 52b3c60..1ed5f2a 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -337,6 +337,7 @@ struct mhi_controller_config {
  * @wlock: Lock for protecting device wakeup
  * @mhi_link_info: Device bandwidth info
  * @st_worker: State transition worker
+ * @hiprio_wq: High priority workqueue for MHI work such as state transitions
  * @state_event: State change event
  * @status_cb: CB function to notify power states of the device (required)
  * @wake_get: CB function to assert device wake (optional)
@@ -419,6 +420,7 @@ struct mhi_controller {
 	spinlock_t wlock;
 	struct mhi_link_info mhi_link_info;
 	struct work_struct st_worker;
+	struct workqueue_struct *hiprio_wq;
 	wait_queue_head_t state_event;
 
 	void (*status_cb)(struct mhi_controller *mhi_cntrl,
-- 
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