1 files changed, 475 insertions, 115 deletions

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 4c03d6933646..2c31563fdcae 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -11,6 +11,11 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
+ *
+ * TODO:
+ *  - Rework topology
+ *  - s/chip_id/chip_loc
+ *  - s/cfam/chip (cfam_id -> chip_id etc...)
  */
 
 #include <linux/crc4.h>
@@ -21,6 +26,9 @@
 #include <linux/of.h>
 #include <linux/slab.h>
 #include <linux/bitops.h>
+#include <linux/cdev.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
 
 #include "fsi-master.h"
 
@@ -78,9 +86,15 @@ static DEFINE_IDA(master_ida);
 struct fsi_slave {
 	struct device		dev;
 	struct fsi_master	*master;
-	int			id;
-	int			link;
+	struct cdev		cdev;
+	int			cdev_idx;
+	int			id;	/* FSI address */
+	int			link;	/* FSI link# */
+	u32			cfam_id;
+	int			chip_id;
 	uint32_t		size;	/* size of slave address space */
+	u8			t_send_delay;
+	u8			t_echo_delay;
 };
 
 #define to_fsi_master(d) container_of(d, struct fsi_master, dev)
@@ -89,6 +103,13 @@ struct fsi_slave {
 static const int slave_retries = 2;
 static int discard_errors;
 
+static dev_t fsi_base_dev;
+static DEFINE_IDA(fsi_minor_ida);
+#define FSI_CHAR_MAX_DEVICES	0x1000
+
+/* Legacy /dev numbering: 4 devices per chip, 16 chips */
+#define FSI_CHAR_LEGACY_TOP	64
+
 static int fsi_master_read(struct fsi_master *master, int link,
 		uint8_t slave_id, uint32_t addr, void *val, size_t size);
 static int fsi_master_write(struct fsi_master *master, int link,
@@ -190,7 +211,7 @@ static int fsi_slave_calc_addr(struct fsi_slave *slave, uint32_t *addrp,
 static int fsi_slave_report_and_clear_errors(struct fsi_slave *slave)
 {
 	struct fsi_master *master = slave->master;
-	uint32_t irq, stat;
+	__be32 irq, stat;
 	int rc, link;
 	uint8_t id;
 
@@ -215,7 +236,53 @@ static int fsi_slave_report_and_clear_errors(struct fsi_slave *slave)
 			&irq, sizeof(irq));
 }
 
-static int fsi_slave_set_smode(struct fsi_master *master, int link, int id);
+/* Encode slave local bus echo delay */
+static inline uint32_t fsi_smode_echodly(int x)
+{
+	return (x & FSI_SMODE_ED_MASK) << FSI_SMODE_ED_SHIFT;
+}
+
+/* Encode slave local bus send delay */
+static inline uint32_t fsi_smode_senddly(int x)
+{
+	return (x & FSI_SMODE_SD_MASK) << FSI_SMODE_SD_SHIFT;
+}
+
+/* Encode slave local bus clock rate ratio */
+static inline uint32_t fsi_smode_lbcrr(int x)
+{
+	return (x & FSI_SMODE_LBCRR_MASK) << FSI_SMODE_LBCRR_SHIFT;
+}
+
+/* Encode slave ID */
+static inline uint32_t fsi_smode_sid(int x)
+{
+	return (x & FSI_SMODE_SID_MASK) << FSI_SMODE_SID_SHIFT;
+}
+
+static uint32_t fsi_slave_smode(int id, u8 t_senddly, u8 t_echodly)
+{
+	return FSI_SMODE_WSC | FSI_SMODE_ECRC
+		| fsi_smode_sid(id)
+		| fsi_smode_echodly(t_echodly - 1) | fsi_smode_senddly(t_senddly - 1)
+		| fsi_smode_lbcrr(0x8);
+}
+
+static int fsi_slave_set_smode(struct fsi_slave *slave)
+{
+	uint32_t smode;
+	__be32 data;
+
+	/* set our smode register with the slave ID field to 0; this enables
+	 * extended slave addressing
+	 */
+	smode = fsi_slave_smode(slave->id, slave->t_send_delay, slave->t_echo_delay);
+	data = cpu_to_be32(smode);
+
+	return fsi_master_write(slave->master, slave->link, slave->id,
+				FSI_SLAVE_BASE + FSI_SMODE,
+				&data, sizeof(data));
+}
 
 static int fsi_slave_handle_error(struct fsi_slave *slave, bool write,
 				  uint32_t addr, size_t size)
@@ -223,7 +290,7 @@ static int fsi_slave_handle_error(struct fsi_slave *slave, bool write,
 	struct fsi_master *master = slave->master;
 	int rc, link;
 	uint32_t reg;
-	uint8_t id;
+	uint8_t id, send_delay, echo_delay;
 
 	if (discard_errors)
 		return -1;
@@ -254,15 +321,26 @@ static int fsi_slave_handle_error(struct fsi_slave *slave, bool write,
 		}
 	}
 
+	send_delay = slave->t_send_delay;
+	echo_delay = slave->t_echo_delay;
+
 	/* getting serious, reset the slave via BREAK */
 	rc = fsi_master_break(master, link);
 	if (rc)
 		return rc;
 
-	rc = fsi_slave_set_smode(master, link, id);
+	slave->t_send_delay = send_delay;
+	slave->t_echo_delay = echo_delay;
+
+	rc = fsi_slave_set_smode(slave);
 	if (rc)
 		return rc;
 
+	if (master->link_config)
+		master->link_config(master, link,
+				    slave->t_send_delay,
+				    slave->t_echo_delay);
+
 	return fsi_slave_report_and_clear_errors(slave);
 }
 
@@ -390,7 +468,6 @@ static struct device_node *fsi_device_find_of_node(struct fsi_device *dev)
 static int fsi_slave_scan(struct fsi_slave *slave)
 {
 	uint32_t engine_addr;
-	uint32_t conf;
 	int rc, i;
 
 	/*
@@ -404,15 +481,17 @@ static int fsi_slave_scan(struct fsi_slave *slave)
 	for (i = 2; i < engine_page_size / sizeof(uint32_t); i++) {
 		uint8_t slots, version, type, crc;
 		struct fsi_device *dev;
+		uint32_t conf;
+		__be32 data;
 
-		rc = fsi_slave_read(slave, (i + 1) * sizeof(conf),
-				&conf, sizeof(conf));
+		rc = fsi_slave_read(slave, (i + 1) * sizeof(data),
+				&data, sizeof(data));
 		if (rc) {
 			dev_warn(&slave->dev,
 				"error reading slave registers\n");
 			return -1;
 		}
-		conf = be32_to_cpu(conf);
+		conf = be32_to_cpu(data);
 
 		crc = crc4(0, conf, 32);
 		if (crc) {
@@ -539,79 +618,11 @@ static const struct bin_attribute fsi_slave_raw_attr = {
 	.write = fsi_slave_sysfs_raw_write,
 };
 
-static ssize_t fsi_slave_sysfs_term_write(struct file *file,
-		struct kobject *kobj, struct bin_attribute *attr,
-		char *buf, loff_t off, size_t count)
-{
-	struct fsi_slave *slave = to_fsi_slave(kobj_to_dev(kobj));
-	struct fsi_master *master = slave->master;
-
-	if (!master->term)
-		return -ENODEV;
-
-	master->term(master, slave->link, slave->id);
-	return count;
-}
-
-static const struct bin_attribute fsi_slave_term_attr = {
-	.attr = {
-		.name = "term",
-		.mode = 0200,
-	},
-	.size = 0,
-	.write = fsi_slave_sysfs_term_write,
-};
-
-/* Encode slave local bus echo delay */
-static inline uint32_t fsi_smode_echodly(int x)
-{
-	return (x & FSI_SMODE_ED_MASK) << FSI_SMODE_ED_SHIFT;
-}
-
-/* Encode slave local bus send delay */
-static inline uint32_t fsi_smode_senddly(int x)
-{
-	return (x & FSI_SMODE_SD_MASK) << FSI_SMODE_SD_SHIFT;
-}
-
-/* Encode slave local bus clock rate ratio */
-static inline uint32_t fsi_smode_lbcrr(int x)
-{
-	return (x & FSI_SMODE_LBCRR_MASK) << FSI_SMODE_LBCRR_SHIFT;
-}
-
-/* Encode slave ID */
-static inline uint32_t fsi_smode_sid(int x)
-{
-	return (x & FSI_SMODE_SID_MASK) << FSI_SMODE_SID_SHIFT;
-}
-
-static uint32_t fsi_slave_smode(int id)
-{
-	return FSI_SMODE_WSC | FSI_SMODE_ECRC
-		| fsi_smode_sid(id)
-		| fsi_smode_echodly(0xf) | fsi_smode_senddly(0xf)
-		| fsi_smode_lbcrr(0x8);
-}
-
-static int fsi_slave_set_smode(struct fsi_master *master, int link, int id)
-{
-	uint32_t smode;
-
-	/* set our smode register with the slave ID field to 0; this enables
-	 * extended slave addressing
-	 */
-	smode = fsi_slave_smode(id);
-	smode = cpu_to_be32(smode);
-
-	return fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SMODE,
-			&smode, sizeof(smode));
-}
-
 static void fsi_slave_release(struct device *dev)
 {
 	struct fsi_slave *slave = to_fsi_slave(dev);
 
+	fsi_free_minor(slave->dev.devt);
 	of_node_put(dev->of_node);
 	kfree(slave);
 }
@@ -659,11 +670,303 @@ static struct device_node *fsi_slave_find_of_node(struct fsi_master *master,
 	return NULL;
 }
 
+static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
+			 loff_t *offset)
+{
+	struct fsi_slave *slave = filep->private_data;
+	size_t total_len, read_len;
+	loff_t off = *offset;
+	ssize_t rc;
+
+	if (off < 0)
+		return -EINVAL;
+
+	if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
+		return -EINVAL;
+
+	for (total_len = 0; total_len < count; total_len += read_len) {
+		__be32 data;
+
+		read_len = min_t(size_t, count, 4);
+		read_len -= off & 0x3;
+
+		rc = fsi_slave_read(slave, off, &data, read_len);
+		if (rc)
+			goto fail;
+		rc = copy_to_user(buf + total_len, &data, read_len);
+		if (rc) {
+			rc = -EFAULT;
+			goto fail;
+		}
+		off += read_len;
+	}
+	rc = count;
+ fail:
+	*offset = off;
+	return count;
+}
+
+static ssize_t cfam_write(struct file *filep, const char __user *buf,
+			  size_t count, loff_t *offset)
+{
+	struct fsi_slave *slave = filep->private_data;
+	size_t total_len, write_len;
+	loff_t off = *offset;
+	ssize_t rc;
+
+
+	if (off < 0)
+		return -EINVAL;
+
+	if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
+		return -EINVAL;
+
+	for (total_len = 0; total_len < count; total_len += write_len) {
+		__be32 data;
+
+		write_len = min_t(size_t, count, 4);
+		write_len -= off & 0x3;
+
+		rc = copy_from_user(&data, buf + total_len, write_len);
+		if (rc) {
+			rc = -EFAULT;
+			goto fail;
+		}
+		rc = fsi_slave_write(slave, off, &data, write_len);
+		if (rc)
+			goto fail;
+		off += write_len;
+	}
+	rc = count;
+ fail:
+	*offset = off;
+	return count;
+}
+
+static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)
+{
+	switch (whence) {
+	case SEEK_CUR:
+		break;
+	case SEEK_SET:
+		file->f_pos = offset;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return offset;
+}
+
+static int cfam_open(struct inode *inode, struct file *file)
+{
+	struct fsi_slave *slave = container_of(inode->i_cdev, struct fsi_slave, cdev);
+
+	file->private_data = slave;
+
+	return 0;
+}
+
+static const struct file_operations cfam_fops = {
+	.owner		= THIS_MODULE,
+	.open		= cfam_open,
+	.llseek		= cfam_llseek,
+	.read		= cfam_read,
+	.write		= cfam_write,
+};
+
+static ssize_t send_term_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	struct fsi_slave *slave = to_fsi_slave(dev);
+	struct fsi_master *master = slave->master;
+
+	if (!master->term)
+		return -ENODEV;
+
+	master->term(master, slave->link, slave->id);
+	return count;
+}
+
+static DEVICE_ATTR_WO(send_term);
+
+static ssize_t slave_send_echo_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct fsi_slave *slave = to_fsi_slave(dev);
+
+	return sprintf(buf, "%u\n", slave->t_send_delay);
+}
+
+static ssize_t slave_send_echo_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct fsi_slave *slave = to_fsi_slave(dev);
+	struct fsi_master *master = slave->master;
+	unsigned long val;
+	int rc;
+
+	if (kstrtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	if (val < 1 || val > 16)
+		return -EINVAL;
+
+	if (!master->link_config)
+		return -ENXIO;
+
+	/* Current HW mandates that send and echo delay are identical */
+	slave->t_send_delay = val;
+	slave->t_echo_delay = val;
+
+	rc = fsi_slave_set_smode(slave);
+	if (rc < 0)
+		return rc;
+	if (master->link_config)
+		master->link_config(master, slave->link,
+				    slave->t_send_delay,
+				    slave->t_echo_delay);
+
+	return count;
+}
+
+static DEVICE_ATTR(send_echo_delays, 0600,
+		   slave_send_echo_show, slave_send_echo_store);
+
+static ssize_t chip_id_show(struct device *dev,
+			    struct device_attribute *attr,
+			    char *buf)
+{
+	struct fsi_slave *slave = to_fsi_slave(dev);
+
+	return sprintf(buf, "%d\n", slave->chip_id);
+}
+
+static DEVICE_ATTR_RO(chip_id);
+
+static ssize_t cfam_id_show(struct device *dev,
+			    struct device_attribute *attr,
+			    char *buf)
+{
+	struct fsi_slave *slave = to_fsi_slave(dev);
+
+	return sprintf(buf, "0x%x\n", slave->cfam_id);
+}
+
+static DEVICE_ATTR_RO(cfam_id);
+
+static struct attribute *cfam_attr[] = {
+	&dev_attr_send_echo_delays.attr,
+	&dev_attr_chip_id.attr,
+	&dev_attr_cfam_id.attr,
+	&dev_attr_send_term.attr,
+	NULL,
+};
+
+static const struct attribute_group cfam_attr_group = {
+	.attrs = cfam_attr,
+};
+
+static const struct attribute_group *cfam_attr_groups[] = {
+	&cfam_attr_group,
+	NULL,
+};
+
+static char *cfam_devnode(struct device *dev, umode_t *mode,
+			  kuid_t *uid, kgid_t *gid)
+{
+	struct fsi_slave *slave = to_fsi_slave(dev);
+
+#ifdef CONFIG_FSI_NEW_DEV_NODE
+	return kasprintf(GFP_KERNEL, "fsi/cfam%d", slave->cdev_idx);
+#else
+	return kasprintf(GFP_KERNEL, "cfam%d", slave->cdev_idx);
+#endif
+}
+
+static const struct device_type cfam_type = {
+	.name = "cfam",
+	.devnode = cfam_devnode,
+	.groups = cfam_attr_groups
+};
+
+static char *fsi_cdev_devnode(struct device *dev, umode_t *mode,
+			      kuid_t *uid, kgid_t *gid)
+{
+#ifdef CONFIG_FSI_NEW_DEV_NODE
+	return kasprintf(GFP_KERNEL, "fsi/%s", dev_name(dev));
+#else
+	return kasprintf(GFP_KERNEL, "%s", dev_name(dev));
+#endif
+}
+
+const struct device_type fsi_cdev_type = {
+	.name = "fsi-cdev",
+	.devnode = fsi_cdev_devnode,
+};
+EXPORT_SYMBOL_GPL(fsi_cdev_type);
+
+/* Backward compatible /dev/ numbering in "old style" mode */
+static int fsi_adjust_index(int index)
+{
+#ifdef CONFIG_FSI_NEW_DEV_NODE
+	return index;
+#else
+	return index + 1;
+#endif
+}
+
+static int __fsi_get_new_minor(struct fsi_slave *slave, enum fsi_dev_type type,
+			       dev_t *out_dev, int *out_index)
+{
+	int cid = slave->chip_id;
+	int id;
+
+	/* Check if we qualify for legacy numbering */
+	if (cid >= 0 && cid < 16 && type < 4) {
+		/* Try reserving the legacy number */
+		id = (cid << 4) | type;
+		id = ida_simple_get(&fsi_minor_ida, id, id + 1, GFP_KERNEL);
+		if (id >= 0) {
+			*out_index = fsi_adjust_index(cid);
+			*out_dev = fsi_base_dev + id;
+			return 0;
+		}
+		/* Other failure */
+		if (id != -ENOSPC)
+			return id;
+		/* Fallback to non-legacy allocation */
+	}
+	id = ida_simple_get(&fsi_minor_ida, FSI_CHAR_LEGACY_TOP,
+			    FSI_CHAR_MAX_DEVICES, GFP_KERNEL);
+	if (id < 0)
+		return id;
+	*out_index = fsi_adjust_index(id);
+	*out_dev = fsi_base_dev + id;
+	return 0;
+}
+
+int fsi_get_new_minor(struct fsi_device *fdev, enum fsi_dev_type type,
+		      dev_t *out_dev, int *out_index)
+{
+	return __fsi_get_new_minor(fdev->slave, type, out_dev, out_index);
+}
+EXPORT_SYMBOL_GPL(fsi_get_new_minor);
+
+void fsi_free_minor(dev_t dev)
+{
+	ida_simple_remove(&fsi_minor_ida, MINOR(dev));
+}
+EXPORT_SYMBOL_GPL(fsi_free_minor);
+
 static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 {
-	uint32_t chip_id, llmode;
+	uint32_t cfam_id;
 	struct fsi_slave *slave;
 	uint8_t crc;
+	__be32 data, llmode;
 	int rc;
 
 	/* Currently, we only support single slaves on a link, and use the
@@ -672,31 +975,23 @@ static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 	if (id != 0)
 		return -EINVAL;
 
-	rc = fsi_master_read(master, link, id, 0, &chip_id, sizeof(chip_id));
+	rc = fsi_master_read(master, link, id, 0, &data, sizeof(data));
 	if (rc) {
 		dev_dbg(&master->dev, "can't read slave %02x:%02x %d\n",
 				link, id, rc);
 		return -ENODEV;
 	}
-	chip_id = be32_to_cpu(chip_id);
+	cfam_id = be32_to_cpu(data);
 
-	crc = crc4(0, chip_id, 32);
+	crc = crc4(0, cfam_id, 32);
 	if (crc) {
-		dev_warn(&master->dev, "slave %02x:%02x invalid chip id CRC!\n",
+		dev_warn(&master->dev, "slave %02x:%02x invalid cfam id CRC!\n",
 				link, id);
 		return -EIO;
 	}
 
 	dev_dbg(&master->dev, "fsi: found chip %08x at %02x:%02x:%02x\n",
-			chip_id, master->idx, link, id);
-
-	rc = fsi_slave_set_smode(master, link, id);
-	if (rc) {
-		dev_warn(&master->dev,
-				"can't set smode on slave:%02x:%02x %d\n",
-				link, id, rc);
-		return -ENODEV;
-	}
+			cfam_id, master->idx, link, id);
 
 	/* If we're behind a master that doesn't provide a self-running bus
 	 * clock, put the slave into async mode
@@ -719,30 +1014,61 @@ static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 	if (!slave)
 		return -ENOMEM;
 
-	slave->master = master;
+	dev_set_name(&slave->dev, "slave@%02x:%02x", link, id);
+	slave->dev.type = &cfam_type;
 	slave->dev.parent = &master->dev;
 	slave->dev.of_node = fsi_slave_find_of_node(master, link, id);
 	slave->dev.release = fsi_slave_release;
+	device_initialize(&slave->dev);
+	slave->cfam_id = cfam_id;
+	slave->master = master;
 	slave->link = link;
 	slave->id = id;
 	slave->size = FSI_SLAVE_SIZE_23b;
+	slave->t_send_delay = 16;
+	slave->t_echo_delay = 16;
+
+	/* Get chip ID if any */
+	slave->chip_id = -1;
+	if (slave->dev.of_node) {
+		uint32_t prop;
+		if (!of_property_read_u32(slave->dev.of_node, "chip-id", &prop))
+			slave->chip_id = prop;
 
-	dev_set_name(&slave->dev, "slave@%02x:%02x", link, id);
-	rc = device_register(&slave->dev);
-	if (rc < 0) {
-		dev_warn(&master->dev, "failed to create slave device: %d\n",
-				rc);
-		put_device(&slave->dev);
-		return rc;
 	}
 
+	/* Allocate a minor in the FSI space */
+	rc = __fsi_get_new_minor(slave, fsi_dev_cfam, &slave->dev.devt,
+				 &slave->cdev_idx);
+	if (rc)
+		goto err_free;
+
+	/* Create chardev for userspace access */
+	cdev_init(&slave->cdev, &cfam_fops);
+	rc = cdev_device_add(&slave->cdev, &slave->dev);
+	if (rc) {
+		dev_err(&slave->dev, "Error %d creating slave device\n", rc);
+		goto err_free;
+	}
+
+	rc = fsi_slave_set_smode(slave);
+	if (rc) {
+		dev_warn(&master->dev,
+				"can't set smode on slave:%02x:%02x %d\n",
+				link, id, rc);
+		kfree(slave);
+		return -ENODEV;
+	}
+	if (master->link_config)
+		master->link_config(master, link,
+				    slave->t_send_delay,
+				    slave->t_echo_delay);
+
+	/* Legacy raw file -> to be removed */
 	rc = device_create_bin_file(&slave->dev, &fsi_slave_raw_attr);
 	if (rc)
 		dev_warn(&slave->dev, "failed to create raw attr: %d\n", rc);
 
-	rc = device_create_bin_file(&slave->dev, &fsi_slave_term_attr);
-	if (rc)
-		dev_warn(&slave->dev, "failed to create term attr: %d\n", rc);
 
 	rc = fsi_slave_scan(slave);
 	if (rc)
@@ -750,6 +1076,10 @@ static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
 				rc);
 
 	return rc;
+
+ err_free:
+	put_device(&slave->dev);
+	return rc;
 }
 
 /* FSI master support */
@@ -814,12 +1144,16 @@ static int fsi_master_link_enable(struct fsi_master *master, int link)
  */
 static int fsi_master_break(struct fsi_master *master, int link)
 {
+	int rc = 0;
+
 	trace_fsi_master_break(master, link);
 
 	if (master->send_break)
-		return master->send_break(master, link);
+		rc = master->send_break(master, link);
+	if (master->link_config)
+		master->link_config(master, link, 16, 16);
 
-	return 0;
+	return rc;
 }
 
 static int fsi_master_scan(struct fsi_master *master)
@@ -854,8 +1188,11 @@ static int fsi_slave_remove_device(struct device *dev, void *arg)
 
 static int fsi_master_remove_slave(struct device *dev, void *arg)
 {
+	struct fsi_slave *slave = to_fsi_slave(dev);
+
 	device_for_each_child(dev, NULL, fsi_slave_remove_device);
-	device_unregister(dev);
+	cdev_device_del(&slave->cdev, &slave->dev);
+	put_device(dev);
 	return 0;
 }
 
@@ -866,8 +1203,14 @@ static void fsi_master_unscan(struct fsi_master *master)
 
 int fsi_master_rescan(struct fsi_master *master)
 {
+	int rc;
+
+	mutex_lock(&master->scan_lock);
 	fsi_master_unscan(master);
-	return fsi_master_scan(master);
+	rc = fsi_master_scan(master);
+	mutex_unlock(&master->scan_lock);
+
+	return rc;
 }
 EXPORT_SYMBOL_GPL(fsi_master_rescan);
 
@@ -903,9 +1246,7 @@ int fsi_master_register(struct fsi_master *master)
 	int rc;
 	struct device_node *np;
 
-	if (!master)
-		return -EINVAL;
-
+	mutex_init(&master->scan_lock);
 	master->idx = ida_simple_get(&master_ida, 0, INT_MAX, GFP_KERNEL);
 	dev_set_name(&master->dev, "fsi%d", master->idx);
 
@@ -917,21 +1258,24 @@ int fsi_master_register(struct fsi_master *master)
 
 	rc = device_create_file(&master->dev, &dev_attr_rescan);
 	if (rc) {
-		device_unregister(&master->dev);
+		device_del(&master->dev);
 		ida_simple_remove(&master_ida, master->idx);
 		return rc;
 	}
 
 	rc = device_create_file(&master->dev, &dev_attr_break);
 	if (rc) {
-		device_unregister(&master->dev);
+		device_del(&master->dev);
 		ida_simple_remove(&master_ida, master->idx);
 		return rc;
 	}
 
 	np = dev_of_node(&master->dev);
-	if (!of_property_read_bool(np, "no-scan-on-init"))
+	if (!of_property_read_bool(np, "no-scan-on-init")) {
+		mutex_lock(&master->scan_lock);
 		fsi_master_scan(master);
+		mutex_unlock(&master->scan_lock);
+	}
 
 	return 0;
 }
@@ -944,7 +1288,9 @@ void fsi_master_unregister(struct fsi_master *master)
 		master->idx = -1;
 	}
 
+	mutex_lock(&master->scan_lock);
 	fsi_master_unscan(master);
+	mutex_unlock(&master->scan_lock);
 	device_unregister(&master->dev);
 }
 EXPORT_SYMBOL_GPL(fsi_master_unregister);
@@ -996,13 +1342,27 @@ EXPORT_SYMBOL_GPL(fsi_bus_type);
 
 static int __init fsi_init(void)
 {
-	return bus_register(&fsi_bus_type);
+	int rc;
+
+	rc = alloc_chrdev_region(&fsi_base_dev, 0, FSI_CHAR_MAX_DEVICES, "fsi");
+	if (rc)
+		return rc;
+	rc = bus_register(&fsi_bus_type);
+	if (rc)
+		goto fail_bus;
+	return 0;
+
+ fail_bus:
+	unregister_chrdev_region(fsi_base_dev, FSI_CHAR_MAX_DEVICES);
+	return rc;
 }
 postcore_initcall(fsi_init);
 
 static void fsi_exit(void)
 {
 	bus_unregister(&fsi_bus_type);
+	unregister_chrdev_region(fsi_base_dev, FSI_CHAR_MAX_DEVICES);
+	ida_destroy(&fsi_minor_ida);
 }
 module_exit(fsi_exit);
 module_param(discard_errors, int, 0664);