diff --git a/drivers/fsi/Kconfig b/drivers/fsi/Kconfig
index af3a20d..ea2f4a1 100644
--- a/drivers/fsi/Kconfig
+++ b/drivers/fsi/Kconfig
@@ -64,4 +64,14 @@ config FSI_SBEFIFO
 	a pipe-like FSI device for communicating with the self boot engine
 	(SBE) on POWER processors.
 
+config FSI_OCC
+	tristate "OCC SBEFIFO client device driver"
+	depends on FSI_SBEFIFO
+	---help---
+	This option enables an SBEFIFO based On-Chip Controller (OCC) device
+	driver. The OCC is a device embedded on a POWER processor that collects
+	and aggregates sensor data from the processor and system. The OCC can
+	provide the raw sensor data as well as perform thermal and power
+	management on the system.
+
 endif
diff --git a/drivers/fsi/Makefile b/drivers/fsi/Makefile
index a50d6ce..62687ec 100644
--- a/drivers/fsi/Makefile
+++ b/drivers/fsi/Makefile
@@ -5,3 +5,4 @@ obj-$(CONFIG_FSI_MASTER_GPIO) += fsi-master-gpio.o
 obj-$(CONFIG_FSI_MASTER_AST_CF) += fsi-master-ast-cf.o
 obj-$(CONFIG_FSI_SCOM) += fsi-scom.o
 obj-$(CONFIG_FSI_SBEFIFO) += fsi-sbefifo.o
+obj-$(CONFIG_FSI_OCC) += fsi-occ.o
diff --git a/drivers/fsi/fsi-occ.c b/drivers/fsi/fsi-occ.c
new file mode 100644
index 0000000..2a2049d
--- /dev/null
+++ b/drivers/fsi/fsi-occ.c
@@ -0,0 +1,599 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/fsi-sbefifo.h>
+#include <linux/gfp.h>
+#include <linux/idr.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/fsi-occ.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <asm/unaligned.h>
+
+#define OCC_SRAM_BYTES		4096
+#define OCC_CMD_DATA_BYTES	4090
+#define OCC_RESP_DATA_BYTES	4089
+
+#define OCC_SRAM_CMD_ADDR	0xFFFBE000
+#define OCC_SRAM_RSP_ADDR	0xFFFBF000
+
+/*
+ * Assume we don't have much FFDC, if we do we'll overflow and
+ * fail the command. This needs to be big enough for simple
+ * commands as well.
+ */
+#define OCC_SBE_STATUS_WORDS	32
+
+#define OCC_TIMEOUT_MS		1000
+#define OCC_CMD_IN_PRG_WAIT_MS	50
+
+struct occ {
+	struct device *dev;
+	struct device *sbefifo;
+	char name[32];
+	int idx;
+	struct miscdevice mdev;
+	struct mutex occ_lock;
+};
+
+#define to_occ(x)	container_of((x), struct occ, mdev)
+
+struct occ_response {
+	u8 seq_no;
+	u8 cmd_type;
+	u8 return_status;
+	__be16 data_length;
+	u8 data[OCC_RESP_DATA_BYTES + 2];	/* two bytes checksum */
+} __packed;
+
+struct occ_client {
+	struct occ *occ;
+	struct mutex lock;
+	size_t data_size;
+	size_t read_offset;
+	u8 *buffer;
+};
+
+#define to_client(x)	container_of((x), struct occ_client, xfr)
+
+static DEFINE_IDA(occ_ida);
+
+static int occ_open(struct inode *inode, struct file *file)
+{
+	struct occ_client *client = kzalloc(sizeof(*client), GFP_KERNEL);
+	struct miscdevice *mdev = file->private_data;
+	struct occ *occ = to_occ(mdev);
+
+	if (!client)
+		return -ENOMEM;
+
+	client->buffer = (u8 *)__get_free_page(GFP_KERNEL);
+	if (!client->buffer) {
+		kfree(client);
+		return -ENOMEM;
+	}
+
+	client->occ = occ;
+	mutex_init(&client->lock);
+	file->private_data = client;
+
+	/* We allocate a 1-page buffer, make sure it all fits */
+	BUILD_BUG_ON((OCC_CMD_DATA_BYTES + 3) > PAGE_SIZE);
+	BUILD_BUG_ON((OCC_RESP_DATA_BYTES + 7) > PAGE_SIZE);
+
+	return 0;
+}
+
+static ssize_t occ_read(struct file *file, char __user *buf, size_t len,
+			loff_t *offset)
+{
+	struct occ_client *client = file->private_data;
+	ssize_t rc = 0;
+
+	if (!client)
+		return -ENODEV;
+
+	if (len > OCC_SRAM_BYTES)
+		return -EINVAL;
+
+	mutex_lock(&client->lock);
+
+	/* This should not be possible ... */
+	if (WARN_ON_ONCE(client->read_offset > client->data_size)) {
+		rc = -EIO;
+		goto done;
+	}
+
+	/* Grab how much data we have to read */
+	rc = min(len, client->data_size - client->read_offset);
+	if (copy_to_user(buf, client->buffer + client->read_offset, rc))
+		rc = -EFAULT;
+	else
+		client->read_offset += rc;
+
+ done:
+	mutex_unlock(&client->lock);
+
+	return rc;
+}
+
+static ssize_t occ_write(struct file *file, const char __user *buf,
+			 size_t len, loff_t *offset)
+{
+	struct occ_client *client = file->private_data;
+	size_t rlen, data_length;
+	u16 checksum = 0;
+	ssize_t rc, i;
+	u8 *cmd;
+
+	if (!client)
+		return -ENODEV;
+
+	if (len > (OCC_CMD_DATA_BYTES + 3) || len < 3)
+		return -EINVAL;
+
+	mutex_lock(&client->lock);
+
+	/* Construct the command */
+	cmd = client->buffer;
+
+	/* Sequence number (we could increment and compare with response) */
+	cmd[0] = 1;
+
+	/*
+	 * Copy the user command (assume user data follows the occ command
+	 * format)
+	 * byte 0: command type
+	 * bytes 1-2: data length (msb first)
+	 * bytes 3-n: data
+	 */
+	if (copy_from_user(&cmd[1], buf, len)) {
+		rc = -EFAULT;
+		goto done;
+	}
+
+	/* Extract data length */
+	data_length = (cmd[2] << 8) + cmd[3];
+	if (data_length > OCC_CMD_DATA_BYTES) {
+		rc = -EINVAL;
+		goto done;
+	}
+
+	/* Calculate checksum */
+	for (i = 0; i < data_length + 4; ++i)
+		checksum += cmd[i];
+
+	cmd[data_length + 4] = checksum >> 8;
+	cmd[data_length + 5] = checksum & 0xFF;
+
+	/* Submit command */
+	rlen = PAGE_SIZE;
+	rc = fsi_occ_submit(client->occ->dev, cmd, data_length + 6, cmd,
+			    &rlen);
+	if (rc)
+		goto done;
+
+	/* Set read tracking data */
+	client->data_size = rlen;
+	client->read_offset = 0;
+
+	/* Done */
+	rc = len;
+
+ done:
+	mutex_unlock(&client->lock);
+
+	return rc;
+}
+
+static int occ_release(struct inode *inode, struct file *file)
+{
+	struct occ_client *client = file->private_data;
+
+	free_page((unsigned long)client->buffer);
+	kfree(client);
+
+	return 0;
+}
+
+static const struct file_operations occ_fops = {
+	.owner = THIS_MODULE,
+	.open = occ_open,
+	.read = occ_read,
+	.write = occ_write,
+	.release = occ_release,
+};
+
+static int occ_verify_checksum(struct occ_response *resp, u16 data_length)
+{
+	/* Fetch the two bytes after the data for the checksum. */
+	u16 checksum_resp = get_unaligned_be16(&resp->data[data_length]);
+	u16 checksum;
+	u16 i;
+
+	checksum = resp->seq_no;
+	checksum += resp->cmd_type;
+	checksum += resp->return_status;
+	checksum += (data_length >> 8) + (data_length & 0xFF);
+
+	for (i = 0; i < data_length; ++i)
+		checksum += resp->data[i];
+
+	if (checksum != checksum_resp)
+		return -EBADMSG;
+
+	return 0;
+}
+
+static int occ_getsram(struct occ *occ, u32 address, void *data, ssize_t len)
+{
+	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
+	size_t resp_len, resp_data_len;
+	__be32 *resp, cmd[5];
+	int rc;
+
+	/*
+	 * Magic sequence to do SBE getsram command. SBE will fetch data from
+	 * specified SRAM address.
+	 */
+	cmd[0] = cpu_to_be32(0x5);
+	cmd[1] = cpu_to_be32(SBEFIFO_CMD_GET_OCC_SRAM);
+	cmd[2] = cpu_to_be32(1);
+	cmd[3] = cpu_to_be32(address);
+	cmd[4] = cpu_to_be32(data_len);
+
+	resp_len = (data_len >> 2) + OCC_SBE_STATUS_WORDS;
+	resp = kzalloc(resp_len << 2, GFP_KERNEL);
+	if (!resp)
+		return -ENOMEM;
+
+	rc = sbefifo_submit(occ->sbefifo, cmd, 5, resp, &resp_len);
+	if (rc)
+		goto free;
+
+	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_GET_OCC_SRAM,
+				  resp, resp_len, &resp_len);
+	if (rc)
+		goto free;
+
+	resp_data_len = be32_to_cpu(resp[resp_len - 1]);
+	if (resp_data_len != data_len) {
+		dev_err(occ->dev, "SRAM read expected %d bytes got %zd\n",
+			data_len, resp_data_len);
+		rc = -EBADMSG;
+	} else {
+		memcpy(data, resp, len);
+	}
+
+free:
+	/* Convert positive SBEI status */
+	if (rc > 0) {
+		dev_err(occ->dev, "SRAM read returned failure status: %08x\n",
+			rc);
+		rc = -EBADMSG;
+	}
+
+	kfree(resp);
+	return rc;
+}
+
+static int occ_putsram(struct occ *occ, u32 address, const void *data,
+		       ssize_t len)
+{
+	size_t cmd_len, buf_len, resp_len, resp_data_len;
+	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
+	__be32 *buf;
+	int rc;
+
+	/*
+	 * We use the same buffer for command and response, make
+	 * sure it's big enough
+	 */
+	resp_len = OCC_SBE_STATUS_WORDS;
+	cmd_len = (data_len >> 2) + 5;
+	buf_len = max(cmd_len, resp_len);
+	buf = kzalloc(buf_len << 2, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	/*
+	 * Magic sequence to do SBE putsram command. SBE will transfer
+	 * data to specified SRAM address.
+	 */
+	buf[0] = cpu_to_be32(cmd_len);
+	buf[1] = cpu_to_be32(SBEFIFO_CMD_PUT_OCC_SRAM);
+	buf[2] = cpu_to_be32(1);
+	buf[3] = cpu_to_be32(address);
+	buf[4] = cpu_to_be32(data_len);
+
+	memcpy(&buf[5], data, len);
+
+	rc = sbefifo_submit(occ->sbefifo, buf, cmd_len, buf, &resp_len);
+	if (rc)
+		goto free;
+
+	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
+				  buf, resp_len, &resp_len);
+	if (rc)
+		goto free;
+
+	if (resp_len != 1) {
+		dev_err(occ->dev, "SRAM write response length invalid: %zd\n",
+			resp_len);
+		rc = -EBADMSG;
+	} else {
+		resp_data_len = be32_to_cpu(buf[0]);
+		if (resp_data_len != data_len) {
+			dev_err(occ->dev,
+				"SRAM write expected %d bytes got %zd\n",
+				data_len, resp_data_len);
+			rc = -EBADMSG;
+		}
+	}
+
+free:
+	/* Convert positive SBEI status */
+	if (rc > 0) {
+		dev_err(occ->dev, "SRAM write returned failure status: %08x\n",
+			rc);
+		rc = -EBADMSG;
+	}
+
+	kfree(buf);
+	return rc;
+}
+
+static int occ_trigger_attn(struct occ *occ)
+{
+	__be32 buf[OCC_SBE_STATUS_WORDS];
+	size_t resp_len, resp_data_len;
+	int rc;
+
+	BUILD_BUG_ON(OCC_SBE_STATUS_WORDS < 7);
+	resp_len = OCC_SBE_STATUS_WORDS;
+
+	buf[0] = cpu_to_be32(0x5 + 0x2);        /* Chip-op length in words */
+	buf[1] = cpu_to_be32(SBEFIFO_CMD_PUT_OCC_SRAM);
+	buf[2] = cpu_to_be32(0x3);              /* Mode: Circular */
+	buf[3] = cpu_to_be32(0x0);              /* Address: ignore in mode 3 */
+	buf[4] = cpu_to_be32(0x8);              /* Data length in bytes */
+	buf[5] = cpu_to_be32(0x20010000);       /* Trigger OCC attention */
+	buf[6] = 0;
+
+	rc = sbefifo_submit(occ->sbefifo, buf, 7, buf, &resp_len);
+	if (rc)
+		goto error;
+
+	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
+				  buf, resp_len, &resp_len);
+	if (rc)
+		goto error;
+
+	if (resp_len != 1) {
+		dev_err(occ->dev, "SRAM attn response length invalid: %zd\n",
+			resp_len);
+		rc = -EBADMSG;
+	} else {
+		resp_data_len = be32_to_cpu(buf[0]);
+		if (resp_data_len != 8) {
+			dev_err(occ->dev,
+				"SRAM attn expected 8 bytes got %zd\n",
+				resp_data_len);
+			rc = -EBADMSG;
+		}
+	}
+
+ error:
+	/* Convert positive SBEI status */
+	if (rc > 0) {
+		dev_err(occ->dev, "SRAM attn returned failure status: %08x\n",
+			rc);
+		rc = -EBADMSG;
+	}
+
+	return rc;
+}
+
+int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
+		   void *response, size_t *resp_len)
+{
+	const unsigned long timeout = msecs_to_jiffies(OCC_TIMEOUT_MS);
+	const unsigned long wait_time =
+		msecs_to_jiffies(OCC_CMD_IN_PRG_WAIT_MS);
+	struct occ *occ = dev_get_drvdata(dev);
+	struct occ_response *resp = response;
+	u16 resp_data_length;
+	unsigned long start;
+	int rc;
+
+	if (!occ)
+		return -ENODEV;
+
+	if (*resp_len < 7) {
+		dev_dbg(dev, "Bad resplen %zd\n", *resp_len);
+		return -EINVAL;
+	}
+
+	mutex_lock(&occ->occ_lock);
+
+	rc = occ_putsram(occ, OCC_SRAM_CMD_ADDR, request, req_len);
+	if (rc)
+		goto done;
+
+	rc = occ_trigger_attn(occ);
+	if (rc)
+		goto done;
+
+	/* Read occ response header */
+	start = jiffies;
+	do {
+		rc = occ_getsram(occ, OCC_SRAM_RSP_ADDR, resp, 8);
+		if (rc)
+			goto done;
+
+		if (resp->return_status == OCC_RESP_CMD_IN_PRG) {
+			rc = -ETIMEDOUT;
+
+			if (time_after(jiffies, start + timeout))
+				break;
+
+			set_current_state(TASK_UNINTERRUPTIBLE);
+			schedule_timeout(wait_time);
+		}
+	} while (rc);
+
+	/* Extract size of response data */
+	resp_data_length = get_unaligned_be16(&resp->data_length);
+
+	/* Message size is data length + 5 bytes header + 2 bytes checksum */
+	if ((resp_data_length + 7) > *resp_len) {
+		rc = -EMSGSIZE;
+		goto done;
+	}
+
+	dev_dbg(dev, "resp_status=%02x resp_data_len=%d\n",
+		resp->return_status, resp_data_length);
+
+	/* Grab the rest */
+	if (resp_data_length > 1) {
+		/* already got 3 bytes resp, also need 2 bytes checksum */
+		rc = occ_getsram(occ, OCC_SRAM_RSP_ADDR + 8,
+				 &resp->data[3], resp_data_length - 1);
+		if (rc)
+			goto done;
+	}
+
+	*resp_len = resp_data_length + 7;
+	rc = occ_verify_checksum(resp, resp_data_length);
+
+ done:
+	mutex_unlock(&occ->occ_lock);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(fsi_occ_submit);
+
+static int occ_unregister_child(struct device *dev, void *data)
+{
+	struct platform_device *hwmon_dev = to_platform_device(dev);
+
+	platform_device_unregister(hwmon_dev);
+
+	return 0;
+}
+
+static int occ_probe(struct platform_device *pdev)
+{
+	int rc;
+	u32 reg;
+	struct occ *occ;
+	struct platform_device *hwmon_dev;
+	struct device *dev = &pdev->dev;
+	struct platform_device_info hwmon_dev_info = {
+		.parent = dev,
+		.name = "occ-hwmon",
+	};
+
+	occ = devm_kzalloc(dev, sizeof(*occ), GFP_KERNEL);
+	if (!occ)
+		return -ENOMEM;
+
+	occ->dev = dev;
+	occ->sbefifo = dev->parent;
+	mutex_init(&occ->occ_lock);
+
+	if (dev->of_node) {
+		rc = of_property_read_u32(dev->of_node, "reg", &reg);
+		if (!rc) {
+			/* make sure we don't have a duplicate from dts */
+			occ->idx = ida_simple_get(&occ_ida, reg, reg + 1,
+						  GFP_KERNEL);
+			if (occ->idx < 0)
+				occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX,
+							  GFP_KERNEL);
+		} else {
+			occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX,
+						  GFP_KERNEL);
+		}
+	} else {
+		occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX, GFP_KERNEL);
+	}
+
+	platform_set_drvdata(pdev, occ);
+
+	snprintf(occ->name, sizeof(occ->name), "occ%d", occ->idx);
+	occ->mdev.fops = &occ_fops;
+	occ->mdev.minor = MISC_DYNAMIC_MINOR;
+	occ->mdev.name = occ->name;
+	occ->mdev.parent = dev;
+
+	rc = misc_register(&occ->mdev);
+	if (rc) {
+		dev_err(dev, "failed to register miscdevice: %d\n", rc);
+		ida_simple_remove(&occ_ida, occ->idx);
+		return rc;
+	}
+
+	hwmon_dev_info.id = occ->idx;
+	hwmon_dev = platform_device_register_full(&hwmon_dev_info);
+	if (!hwmon_dev)
+		dev_warn(dev, "failed to create hwmon device\n");
+
+	return 0;
+}
+
+static int occ_remove(struct platform_device *pdev)
+{
+	struct occ *occ = platform_get_drvdata(pdev);
+
+	misc_deregister(&occ->mdev);
+
+	device_for_each_child(&pdev->dev, NULL, occ_unregister_child);
+
+	ida_simple_remove(&occ_ida, occ->idx);
+
+	return 0;
+}
+
+static const struct of_device_id occ_match[] = {
+	{ .compatible = "ibm,p9-occ" },
+	{ },
+};
+
+static struct platform_driver occ_driver = {
+	.driver = {
+		.name = "occ",
+		.of_match_table	= occ_match,
+	},
+	.probe	= occ_probe,
+	.remove = occ_remove,
+};
+
+static int occ_init(void)
+{
+	return platform_driver_register(&occ_driver);
+}
+
+static void occ_exit(void)
+{
+	platform_driver_unregister(&occ_driver);
+
+	ida_destroy(&occ_ida);
+}
+
+module_init(occ_init);
+module_exit(occ_exit);
+
+MODULE_AUTHOR("Eddie James <eajames@linux.vnet.ibm.com>");
+MODULE_DESCRIPTION("BMC P9 OCC driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/fsi-occ.h b/include/linux/fsi-occ.h
new file mode 100644
index 0000000..d4cdc2a
--- /dev/null
+++ b/include/linux/fsi-occ.h
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef LINUX_FSI_OCC_H
+#define LINUX_FSI_OCC_H
+
+struct device;
+
+#define OCC_RESP_CMD_IN_PRG		0xFF
+#define OCC_RESP_SUCCESS		0
+#define OCC_RESP_CMD_INVAL		0x11
+#define OCC_RESP_CMD_LEN_INVAL		0x12
+#define OCC_RESP_DATA_INVAL		0x13
+#define OCC_RESP_CHKSUM_ERR		0x14
+#define OCC_RESP_INT_ERR		0x15
+#define OCC_RESP_BAD_STATE		0x16
+#define OCC_RESP_CRIT_EXCEPT		0xE0
+#define OCC_RESP_CRIT_INIT		0xE1
+#define OCC_RESP_CRIT_WATCHDOG		0xE2
+#define OCC_RESP_CRIT_OCB		0xE3
+#define OCC_RESP_CRIT_HW		0xE4
+
+int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
+		   void *response, size_t *resp_len);
+
+#endif /* LINUX_FSI_OCC_H */
