Date:   Fri, 17 Apr 2020 18:21:02 +0200
From:   Parshuram Thombare <pthombar@...ence.com>
To:     <bbrezillon@...nel.org>, <vitor.soares@...opsys.com>
CC:     <pgaj@...ence.com>, <linux-i3c@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <mparab@...ence.com>,
        <praneeth@...com>, Parshuram Thombare <pthombar@...ence.com>
Subject: [PATCH v6 3/8] i3c: master: i3c mastership request and handover

This patch add I3C mastership request and
handover infrasturcture to I3C master subsystem.

Signed-off-by: Parshuram Thombare <pthombar@...ence.com>
---
 drivers/i3c/master.c       | 221 +++++++++++++++++++++++++++++++++++++
 include/linux/i3c/master.h |  34 ++++++
 2 files changed, 255 insertions(+)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 0ec332e45737..3598856a0b25 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -1217,6 +1217,69 @@ static int i3c_master_getdcr_locked(struct i3c_master_controller *master,
 	return ret;
 }
 
+static int i3c_master_get_accmst_locked(struct i3c_master_controller *master,
+					u8 addr)
+{
+	struct i3c_ccc_getaccmst *accmst;
+	struct i3c_ccc_cmd_dest dest;
+	struct i3c_ccc_cmd cmd;
+	int ret;
+
+	accmst = i3c_ccc_cmd_dest_init(&dest, addr, sizeof(*accmst));
+	if (!accmst)
+		return -ENOMEM;
+
+	i3c_ccc_cmd_init(&cmd, true, I3C_CCC_GETACCMST, &dest, 1);
+
+	ret = i3c_master_send_ccc_cmd_locked(master, &cmd);
+	if (ret)
+		goto out;
+
+	if (dest.payload.len != sizeof(*accmst))
+		ret = -EIO;
+
+out:
+	i3c_ccc_cmd_dest_cleanup(&dest);
+
+	return ret;
+}
+
+static int i3c_master_enable_mr_events(struct i3c_master_controller *master)
+{
+	int ret;
+
+	master->ops->enable_mr_events(master);
+	i3c_bus_maintenance_lock(&master->bus);
+	ret = i3c_master_enec_locked(master, I3C_BROADCAST_ADDR,
+				     I3C_CCC_EVENT_MR | I3C_CCC_EVENT_HJ);
+	i3c_bus_maintenance_unlock(&master->bus);
+
+	return ret;
+}
+
+static int i3c_master_getaccmst(struct i3c_master_controller *master)
+{
+	int ret;
+
+	i3c_bus_maintenance_lock(&master->bus);
+	ret = i3c_master_get_accmst_locked(master, master->mr_addr);
+	i3c_bus_maintenance_unlock(&master->bus);
+
+	return ret;
+}
+
+static int i3c_master_request_mastership(struct i3c_master_controller *master)
+{
+	int ret;
+
+	/* request_mastership callback should handle EN/DIS EC MR.*/
+	i3c_bus_maintenance_lock(&master->bus);
+	ret = master->ops->request_mastership(master);
+	i3c_bus_maintenance_unlock(&master->bus);
+
+	return ret;
+}
+
 static int i3c_master_retrieve_dev_info(struct i3c_dev_desc *dev)
 {
 	struct i3c_master_controller *master = i3c_dev_get_master(dev);
@@ -1612,6 +1675,161 @@ static void i3c_master_detach_free_devs(struct i3c_master_controller *master)
 	}
 }
 
+static void i3c_mst_yield_bus(struct work_struct *work)
+{
+	struct i3c_master_controller *m;
+	struct i3c_dev_desc *i3cdev;
+	int ret;
+
+	m = container_of(work, struct i3c_master_controller, mst_work);
+
+	switch (m->mr_state) {
+	case I3C_MR_DISEC_MR:
+		/*
+		 * Disable MR on all but the secondary master first
+		 * reaching here.
+		 */
+		i3c_bus_for_each_i3cdev(&m->bus, i3cdev) {
+			if (I3C_BCR_DEVICE_ROLE(i3cdev->info.bcr) !=
+			    I3C_BCR_I3C_MASTER ||
+			    i3cdev->info.dyn_addr == m->mr_addr ||
+			    m->this == i3cdev)
+				continue;
+			i3c_bus_maintenance_lock(&m->bus);
+			i3c_master_disec_locked(m, i3cdev->info.dyn_addr,
+						I3C_CCC_EVENT_MR |
+						I3C_CCC_EVENT_HJ);
+			i3c_bus_maintenance_unlock(&m->bus);
+		}
+		m->mr_state = I3C_MR_GETACCMST;
+		queue_work(m->wq, &m->mst_work);
+		break;
+
+	case I3C_MR_GETACCMST:
+		ret = i3c_master_getaccmst(m);
+		if (!ret)
+			m->mr_state = I3C_MR_DONE;
+		else
+			m->mr_state = I3C_MR_FAILED;
+		queue_work(m->wq, &m->mst_work);
+		break;
+
+	case I3C_MR_DONE:
+		i3c_bus_for_each_i3cdev(&m->bus, i3cdev) {
+			if (m->mr_addr == i3cdev->info.dyn_addr) {
+				m->bus.cur_master = i3cdev;
+				break;
+			}
+		}
+		m->mr_state = I3C_MR_IDLE;
+		break;
+
+	default:
+	case I3C_MR_FAILED:
+		i3c_master_enable_mr_events(m);
+		m->mr_state = I3C_MR_IDLE;
+		break;
+	}
+}
+
+void
+i3c_master_yield_bus(struct i3c_master_controller *master, u8 sec_mst_dyn_addr)
+{
+	if (master->this && master->this == master->bus.cur_master) {
+		master->ops->disable_mr_events(master);
+		master->mr_addr = sec_mst_dyn_addr;
+		master->mr_state = I3C_MR_DISEC_MR;
+		queue_work(master->wq, &master->mst_work);
+	} else {
+		/* If not a current master, we should never come here */
+		WARN_ON(1);
+	}
+}
+EXPORT_SYMBOL_GPL(i3c_master_yield_bus);
+
+static void i3c_sec_mst_acquire_bus(struct work_struct *work)
+{
+	struct i3c_master_controller *m;
+	struct i3c_bus *i3cbus;
+	int ret;
+
+	m = container_of(work, struct i3c_master_controller, sec_mst_work);
+	i3cbus = i3c_master_get_bus(m);
+
+	switch (m->mr_state) {
+	case I3C_MR_WAIT_DA:
+		/* Wait until this master have dynamic address */
+		if (m->ops->check_event_set(m, I3C_SLV_DA_UPDATE))
+			m->mr_state = I3C_MR_REQUEST;
+		queue_work(m->wq, &m->sec_mst_work);
+		break;
+
+	case I3C_MR_REQUEST:
+		/* Wait until we can send MR */
+		ret = i3c_master_request_mastership(m);
+		if (!ret)
+			m->mr_state = I3C_MR_WAIT_MR_DONE;
+		queue_work(m->wq, &m->sec_mst_work);
+		break;
+
+	case I3C_MR_WAIT_MR_DONE:
+		if (m->ops->check_event_set(m, I3C_SLV_MR_DONE)) {
+			m->mr_state = I3C_MR_DONE;
+			m->bus.cur_master = m->this;
+			complete(&m->mr_comp);
+		} else {
+			queue_work(m->wq, &m->sec_mst_work);
+		}
+		break;
+
+	default:
+		m->mr_state = I3C_MR_FAILED;
+		complete(&m->mr_comp);
+		break;
+	}
+}
+
+void i3c_sec_mst_mr_dis_event(struct i3c_master_controller *m)
+{
+	if (m->mr_state != I3C_MR_IDLE)
+		m->mr_state = I3C_MR_WAIT_DA;
+}
+EXPORT_SYMBOL_GPL(i3c_sec_mst_mr_dis_event);
+
+/* This function is expected to be called with normaluse_lock */
+int i3c_master_acquire_bus(struct i3c_master_controller *master)
+{
+	int ret = 0;
+
+	if (!master->this || master->this != master->bus.cur_master) {
+		if (master->mr_state == I3C_MR_IDLE) {
+			master->mr_state = I3C_MR_WAIT_DA;
+			init_completion(&master->mr_comp);
+			queue_work(master->wq, &master->sec_mst_work);
+			/*
+			 * Bus acquire procedure may need write lock
+			 * so release read lock before yielding
+			 * to bus acquire state machine
+			 */
+			i3c_bus_normaluse_unlock(&master->bus);
+			wait_for_completion(&master->mr_comp);
+			i3c_bus_normaluse_lock(&master->bus);
+			if (master->mr_state != I3C_MR_DONE)
+				ret = -EAGAIN;
+			master->mr_state = I3C_MR_IDLE;
+		} else {
+			/*
+			 * MR request is already in process for
+			 * this master
+			 */
+			ret = -EAGAIN;
+		}
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(i3c_master_acquire_bus);
+
 /**
  * i3c_master_bus_init() - initialize an I3C bus
  * @master: main master initializing the bus
@@ -2451,6 +2669,9 @@ int i3c_master_register(struct i3c_master_controller *master,
 	device_initialize(&master->dev);
 	dev_set_name(&master->dev, "i3c-%d", i3cbus->id);
 
+	INIT_WORK(&master->sec_mst_work, i3c_sec_mst_acquire_bus);
+	INIT_WORK(&master->mst_work, i3c_mst_yield_bus);
+
 	ret = of_populate_i3c_bus(master);
 	if (ret)
 		goto err_put_dev;
diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index 3dc7eafe811a..c465c7792ccb 100644
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -259,6 +259,27 @@ enum i3c_bus_mode {
 	I3C_BUS_MODE_MIXED_SLOW,
 };
 
+enum i3c_mr_state {
+	I3C_MR_IDLE,
+	I3C_MR_DISEC_MR,
+	I3C_MR_SEND_DEFSLVS,
+	I3C_MR_GETACCMST,
+	I3C_MR_WAIT_DA,
+	I3C_MR_CHECK_STATE,
+	I3C_MR_REQUEST,
+	I3C_MR_WAIT_DEFSLVS,
+	I3C_MR_WAIT_MR_DONE,
+	I3C_MR_DONE,
+	I3C_MR_FAILED,
+};
+
+enum i3c_event {
+	I3C_SLV_DA_UPDATE,
+	I3C_SLV_DEFSLVS_CCC,
+	I3C_SLV_MR_DIS,
+	I3C_SLV_MR_DONE,
+};
+
 /**
  * enum i3c_addr_slot_status - I3C address slot status
  * @I3C_ADDR_SLOT_FREE: address is free
@@ -448,6 +469,11 @@ struct i3c_master_controller_ops {
 	int (*disable_ibi)(struct i3c_dev_desc *dev);
 	void (*recycle_ibi_slot)(struct i3c_dev_desc *dev,
 				 struct i3c_ibi_slot *slot);
+	int (*request_mastership)(struct i3c_master_controller *master);
+	void (*enable_mr_events)(struct i3c_master_controller *m);
+	void (*disable_mr_events)(struct i3c_master_controller *m);
+	bool (*check_event_set)(struct i3c_master_controller *m,
+				enum i3c_event);
 };
 
 /**
@@ -489,6 +515,11 @@ struct i3c_master_controller {
 	} boardinfo;
 	struct i3c_bus bus;
 	struct workqueue_struct *wq;
+	struct work_struct mst_work;
+	struct work_struct sec_mst_work;
+	struct completion mr_comp;
+	enum i3c_mr_state mr_state;
+	u8 mr_addr;
 };
 
 /**
@@ -513,6 +544,9 @@ struct i3c_master_controller {
 #define i3c_bus_for_each_i3cdev(bus, dev)				\
 	list_for_each_entry(dev, &(bus)->devs.i3c, common.node)
 
+void i3c_master_yield_bus(struct i3c_master_controller *master,
+			  u8 slv_dyn_addr);
+void i3c_sec_mst_mr_dis_event(struct i3c_master_controller *m);
 int i3c_master_do_i2c_xfers(struct i3c_master_controller *master,
 			    const struct i2c_msg *xfers,
 			    int nxfers);
-- 
2.17.1

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