[PATCH v3 14/25] bus: mhi: ep: Add support for managing MHI state machine

Manivannan Sadhasivam
2022-02-12T18:23:05Z

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>
---
drivers/bus/mhi/ep/Makefile | 2 +-
drivers/bus/mhi/ep/internal.h | 11 +++
drivers/bus/mhi/ep/main.c | 51 ++++++++++-
drivers/bus/mhi/ep/sm.c | 168 ++++++++++++++++++++++++++++++++++
include/linux/mhi_ep.h | 6 ++
5 files changed, 236 insertions(+), 2 deletions(-)
create mode 100644 drivers/bus/mhi/ep/sm.c

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 fd63f79c6aec..e4e8f06c2898 100644
--- a/drivers/bus/mhi/ep/internal.h
+++ b/drivers/bus/mhi/ep/internal.h
@@ -173,6 +173,11 @@ 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;
@@ -230,5 +235,11 @@ 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 61f066c6286b..ccb3c2795041 100644
--- a/drivers/bus/mhi/ep/main.c
+++ b/drivers/bus/mhi/ep/main.c
@@ -185,6 +185,43 @@ static void mhi_ep_ring_worker(struct work_struct *work)
}
}

+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",
+ 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\n", itr->state);
+ break;
+ }
+ kfree(itr);
+ }
+}
+
static void mhi_ep_release_device(struct device *dev)
{
struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
@@ -386,6 +423,7 @@ 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_workqueue("mhi_ep_ring_wq", 0, 0);
if (!mhi_cntrl->ring_wq) {
@@ -393,8 +431,16 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
goto err_free_cmd;
}

+ mhi_cntrl->state_wq = alloc_workqueue("mhi_ep_state_wq", 0, 0);
+ 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);
+ spin_lock_init(&mhi_cntrl->state_lock);
mutex_init(&mhi_cntrl->event_lock);

/* Set MHI version and AMSS EE before enumeration */
@@ -405,7 +451,7 @@ 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 */
@@ -433,6 +479,8 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
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:
@@ -448,6 +496,7 @@ 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..68e7f99b9137
--- /dev/null
+++ b/drivers/bus/mhi/ep/sm.c
@@ -0,0 +1,168 @@
+// 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",
+ mhi_state_str(mhi_state),
+ 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, 1);
+
+ mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+ MHISTATUS_MHISTATE_MASK, mhi_state);
+ break;
+ case MHI_STATE_SYS_ERR:
+ mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+ MHISTATUS_SYSERR_MASK, 1);
+
+ mhi_ep_mmio_masked_write(mhi_cntrl, MHISTATUS,
+ MHISTATUS_MHISTATE_MASK, mhi_state);
+ break;
+ case MHI_STATE_M1:
+ case MHI_STATE_M2:
+ dev_err(dev, "MHI state (%s) not supported\n", 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, mhi_state);
+ break;
+ default:
+ dev_err(dev, "Invalid MHI state (%d)\n", 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\n");
+ 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\n");
+ 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\n");
+ 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_state = mhi_ep_mmio_masked_read(mhi_cntrl, MHISTATUS, MHISTATUS_MHISTATE_MASK);
+ is_ready = mhi_ep_mmio_masked_read(mhi_cntrl, 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 -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 062133a68118..72ce30cbe87e 100644
--- a/include/linux/mhi_ep.h
+++ b/include/linux/mhi_ep.h
@@ -65,11 +65,14 @@ struct mhi_ep_db_info {
* @ch_ctx_host_pa: Physical address of host channel context data structure
* @ev_ctx_host_pa: Physical address of host event context data structure
* @cmd_ctx_host_pa: Physical address of 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
@@ -105,12 +108,15 @@ struct mhi_ep_cntrl {
u64 ev_ctx_host_pa;
u64 cmd_ctx_host_pa;

+ 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];

--
2.25.1