bus: mhi: ep: Add support for managing MHI state machine

Add support for managing the MHI state machine by controlling the state
transitions. Only the following MHI state transitions are supported:

1. Ready state
2. M0 state
3. M3 state
4. SYS_ERR state

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

5 files changed, 241 insertions, 2 deletions

diff --git a/drivers/bus/mhi/ep/Makefile b/drivers/bus/mhi/ep/Makefile
index 7ba0e04801eb..aad85f180b70 100644
--- a/drivers/bus/mhi/ep/Makefile
+++ b/drivers/bus/mhi/ep/Makefile
@@ -1,2 +1,2 @@
 obj-$(CONFIG_MHI_BUS_EP) += mhi_ep.o
-mhi_ep-y := main.o mmio.o ring.o
+mhi_ep-y := main.o mmio.o ring.o sm.o
diff --git a/drivers/bus/mhi/ep/internal.h b/drivers/bus/mhi/ep/internal.h
index 3551e673d99a..ec508201c5c0 100644
--- a/drivers/bus/mhi/ep/internal.h
+++ b/drivers/bus/mhi/ep/internal.h
@@ -158,6 +158,11 @@ struct mhi_ep_event {
 	struct mhi_ep_ring ring;
 };
 
+struct mhi_ep_state_transition {
+	struct list_head node;
+	enum mhi_state state;
+};
+
 struct mhi_ep_chan {
 	char *name;
 	struct mhi_ep_device *mhi_dev;
@@ -217,5 +222,11 @@ void mhi_ep_mmio_update_ner(struct mhi_ep_cntrl *mhi_cntrl);
 /* MHI EP core functions */
 int mhi_ep_send_state_change_event(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state state);
 int mhi_ep_send_ee_event(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_ep_execenv exec_env);
+bool mhi_ep_check_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state cur_mhi_state,
+			    enum mhi_state mhi_state);
+int mhi_ep_set_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state mhi_state);
+int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl);
+int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl);
+int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl);
 
 #endif
diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
index e5fc97d877b1..a4d7a55b6ab9 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -179,6 +179,42 @@ err_unlock:
 	spin_unlock_irqrestore(&mhi_cntrl->list_lock, flags);
 }
 
+static void mhi_ep_state_worker(struct work_struct *work)
+{
+	struct mhi_ep_cntrl *mhi_cntrl = container_of(work, struct mhi_ep_cntrl, state_work);
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	struct mhi_ep_state_transition *itr, *tmp;
+	unsigned long flags;
+	LIST_HEAD(head);
+	int ret;
+
+	spin_lock_irqsave(&mhi_cntrl->list_lock, flags);
+	list_splice_tail_init(&mhi_cntrl->st_transition_list, &head);
+	spin_unlock_irqrestore(&mhi_cntrl->list_lock, flags);
+
+	list_for_each_entry_safe(itr, tmp, &head, node) {
+		list_del(&itr->node);
+		dev_dbg(dev, "Handling MHI state transition to %s\n",
+			 TO_MHI_STATE_STR(itr->state));
+
+		switch (itr->state) {
+		case MHI_STATE_M0:
+			ret = mhi_ep_set_m0_state(mhi_cntrl);
+			if (ret)
+				dev_err(dev, "Failed to transition to M0 state\n");
+			break;
+		case MHI_STATE_M3:
+			ret = mhi_ep_set_m3_state(mhi_cntrl);
+			if (ret)
+				dev_err(dev, "Failed to transition to M3 state\n");
+			break;
+		default:
+			dev_err(dev, "Invalid MHI state transition: %d", itr->state);
+			break;
+		}
+	}
+}
+
 static void mhi_ep_release_device(struct device *dev)
 {
 	struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
@@ -384,6 +420,7 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
 	}
 
 	INIT_WORK(&mhi_cntrl->ring_work, mhi_ep_ring_worker);
+	INIT_WORK(&mhi_cntrl->state_work, mhi_ep_state_worker);
 
 	mhi_cntrl->ring_wq = alloc_ordered_workqueue("mhi_ep_ring_wq", WQ_HIGHPRI);
 	if (!mhi_cntrl->ring_wq) {
@@ -391,7 +428,14 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
 		goto err_free_cmd;
 	}
 
+	mhi_cntrl->state_wq = alloc_ordered_workqueue("mhi_ep_state_wq", WQ_HIGHPRI);
+	if (!mhi_cntrl->state_wq) {
+		ret = -ENOMEM;
+		goto err_destroy_ring_wq;
+	}
+
 	INIT_LIST_HEAD(&mhi_cntrl->ch_db_list);
+	INIT_LIST_HEAD(&mhi_cntrl->st_transition_list);
 	spin_lock_init(&mhi_cntrl->list_lock);
 	mutex_init(&mhi_cntrl->event_lock);
 
@@ -403,7 +447,7 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
 	mhi_cntrl->index = ida_alloc(&mhi_ep_cntrl_ida, GFP_KERNEL);
 	if (mhi_cntrl->index < 0) {
 		ret = mhi_cntrl->index;
-		goto err_destroy_ring_wq;
+		goto err_destroy_state_wq;
 	}
 
 	/* Allocate the controller device */
@@ -432,6 +476,8 @@ err_release_dev:
 	put_device(&mhi_dev->dev);
 err_ida_free:
 	ida_free(&mhi_ep_cntrl_ida, mhi_cntrl->index);
+err_destroy_state_wq:
+	destroy_workqueue(mhi_cntrl->state_wq);
 err_destroy_ring_wq:
 	destroy_workqueue(mhi_cntrl->ring_wq);
 err_free_cmd:
@@ -447,6 +493,7 @@ void mhi_ep_unregister_controller(struct mhi_ep_cntrl *mhi_cntrl)
 {
 	struct mhi_ep_device *mhi_dev = mhi_cntrl->mhi_dev;
 
+	destroy_workqueue(mhi_cntrl->state_wq);
 	destroy_workqueue(mhi_cntrl->ring_wq);
 
 	kfree(mhi_cntrl->mhi_cmd);
diff --git a/drivers/bus/mhi/ep/sm.c b/drivers/bus/mhi/ep/sm.c
new file mode 100644
index 000000000000..95cec5c627b4
--- /dev/null
+++ b/drivers/bus/mhi/ep/sm.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Linaro Ltd.
+ * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ */
+
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/mhi_ep.h>
+#include "internal.h"
+
+bool __must_check mhi_ep_check_mhi_state(struct mhi_ep_cntrl *mhi_cntrl,
+					 enum mhi_state cur_mhi_state,
+					 enum mhi_state mhi_state)
+{
+	bool valid = false;
+
+	switch (mhi_state) {
+	case MHI_STATE_READY:
+		valid = (cur_mhi_state == MHI_STATE_RESET);
+		break;
+	case MHI_STATE_M0:
+		valid = (cur_mhi_state == MHI_STATE_READY ||
+			  cur_mhi_state == MHI_STATE_M3);
+		break;
+	case MHI_STATE_M3:
+		valid = (cur_mhi_state == MHI_STATE_M0);
+		break;
+	case MHI_STATE_SYS_ERR:
+		/* Transition to SYS_ERR state is allowed all the time */
+		valid = true;
+		break;
+	default:
+		break;
+	}
+
+	return valid;
+}
+
+int mhi_ep_set_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state mhi_state)
+{
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+
+	if (!mhi_ep_check_mhi_state(mhi_cntrl, mhi_cntrl->mhi_state, mhi_state)) {
+		dev_err(dev, "MHI state change to %s from %s is not allowed!\n",
+			TO_MHI_STATE_STR(mhi_state),
+			TO_MHI_STATE_STR(mhi_cntrl->mhi_state));
+		return -EACCES;
+	}
+
+	switch (mhi_state) {
+	case MHI_STATE_READY:
+		mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+				MHISTATUS_READY_MASK,
+				MHISTATUS_READY_SHIFT, 1);
+
+		mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+				MHISTATUS_MHISTATE_MASK,
+				MHISTATUS_MHISTATE_SHIFT, mhi_state);
+		break;
+	case MHI_STATE_SYS_ERR:
+		mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+				MHISTATUS_SYSERR_MASK,
+				MHISTATUS_SYSERR_SHIFT, 1);
+
+		mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+				MHISTATUS_MHISTATE_MASK,
+				MHISTATUS_MHISTATE_SHIFT, mhi_state);
+		break;
+	case MHI_STATE_M1:
+	case MHI_STATE_M2:
+		dev_err(dev, "MHI state (%s) not supported\n", TO_MHI_STATE_STR(mhi_state));
+		return -EOPNOTSUPP;
+	case MHI_STATE_M0:
+	case MHI_STATE_M3:
+		mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+					  MHISTATUS_MHISTATE_MASK,
+					  MHISTATUS_MHISTATE_SHIFT, mhi_state);
+		break;
+	default:
+		dev_err(dev, "Invalid MHI state (%d)", mhi_state);
+		return -EINVAL;
+	}
+
+	mhi_cntrl->mhi_state = mhi_state;
+
+	return 0;
+}
+
+int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl)
+{
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	enum mhi_state old_state;
+	int ret;
+
+	spin_lock_bh(&mhi_cntrl->state_lock);
+	old_state = mhi_cntrl->mhi_state;
+
+	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M0);
+	if (ret) {
+		spin_unlock_bh(&mhi_cntrl->state_lock);
+		return ret;
+	}
+
+	spin_unlock_bh(&mhi_cntrl->state_lock);
+	/* 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: %d\n", ret);
+		return ret;
+	}
+
+	if (old_state == MHI_STATE_READY) {
+		/* Allow the host to process state change event */
+		mdelay(1);
+
+		/* Send AMSS EE event to host */
+		ret = mhi_ep_send_ee_event(mhi_cntrl, MHI_EP_AMSS_EE);
+		if (ret) {
+			dev_err(dev, "Failed sending AMSS EE event: %d\n", ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+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);
+	if (ret) {
+		spin_unlock_bh(&mhi_cntrl->state_lock);
+		return ret;
+	}
+
+	spin_unlock_bh(&mhi_cntrl->state_lock);
+
+	/* Signal host that the device moved to M3 */
+	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_M3);
+	if (ret) {
+		dev_err(dev, "Failed sending M3 state change event: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl)
+{
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	enum mhi_state mhi_state;
+	int ret, is_ready;
+
+	spin_lock_bh(&mhi_cntrl->state_lock);
+	/* Ensure that the MHISTATUS is set to RESET by host */
+	mhi_ep_mmio_masked_read(mhi_cntrl, MHISTATUS, MHISTATUS_MHISTATE_MASK,
+				 MHISTATUS_MHISTATE_SHIFT, &mhi_state);
+	mhi_ep_mmio_masked_read(mhi_cntrl, MHISTATUS, MHISTATUS_READY_MASK,
+				 MHISTATUS_READY_SHIFT, &is_ready);
+
+	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 -EFAULT;
+	}
+
+	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_READY);
+	spin_unlock_bh(&mhi_cntrl->state_lock);
+
+	return ret;
+}
diff --git a/include/linux/mhi_ep.h b/include/linux/mhi_ep.h
index 591af8d53fc2..08f3fed79d34 100644
--- a/include/linux/mhi_ep.h
+++ b/include/linux/mhi_ep.h
@@ -71,11 +71,14 @@ struct mhi_ep_db_info {
  * @ch_ctx_host_size: Size of the host channel context data structure
  * @ev_ctx_host_size: Size of the host event context data structure
  * @cmd_ctx_host_size: Size of the host command context data structure
+ * @state_wq: Dedicated workqueue for handling MHI state transitions
  * @ring_wq: Dedicated workqueue for processing MHI rings
+ * @state_work: State transition worker
  * @ring_work: Ring worker
  * @ch_db_list: List of queued channel doorbells
  * @st_transition_list: List of state transitions
  * @list_lock: Lock for protecting state transition and channel doorbell lists
+ * @state_lock: Lock for protecting state transitions
  * @event_lock: Lock for protecting event rings
  * @chdb: Array of channel doorbell interrupt info
  * @raise_irq: CB function for raising IRQ to the host
@@ -114,12 +117,15 @@ struct mhi_ep_cntrl {
 	size_t ev_ctx_host_size;
 	size_t cmd_ctx_host_size;
 
+	struct workqueue_struct *state_wq;
 	struct workqueue_struct	*ring_wq;
+	struct work_struct state_work;
 	struct work_struct ring_work;
 
 	struct list_head ch_db_list;
 	struct list_head st_transition_list;
 	spinlock_t list_lock;
+	spinlock_t state_lock;
 	struct mutex event_lock;
 	struct mhi_ep_db_info chdb[4];