Merge tag 'for-linus-6.2-1' of https://github.com/cminyard/linux-ipmi

Pull IPMI updates from Corey Minyard:
 "This includes a number of small fixes, as usual.

  It also includes a new driver for doing the i2c (SSIF) interface
  BMC-side, pretty much completing the BMC side interfaces"

* tag 'for-linus-6.2-1' of https://github.com/cminyard/linux-ipmi:
  ipmi/watchdog: use strscpy() to instead of strncpy()
  ipmi: ssif_bmc: Convert to i2c's .probe_new()
  ipmi: fix use after free in _ipmi_destroy_user()
  ipmi/watchdog: Include <linux/kstrtox.h> when appropriate
  ipmi:ssif: Increase the message retry time
  ipmi: Fix some kernel-doc warnings
  ipmi: ssif_bmc: Use EPOLLIN instead of POLLIN
  ipmi: fix msg stack when IPMI is disconnected
  ipmi: fix memleak when unload ipmi driver
  ipmi: fix long wait in unload when IPMI disconnect
  ipmi: kcs: Poll OBF briefly to reduce OBE latency
  bindings: ipmi: Add binding for SSIF BMC driver
  ipmi: ssif_bmc: Add SSIF BMC driver

9 files changed, 948 insertions, 23 deletions

diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
index 39565cf74b2c..b6c0d35fc1a5 100644
--- a/drivers/char/ipmi/Kconfig
+++ b/drivers/char/ipmi/Kconfig
@@ -169,6 +169,16 @@ config ASPEED_BT_IPMI_BMC
 	  found on Aspeed SOCs (AST2400 and AST2500). The driver
 	  implements the BMC side of the BT interface.
 
+config SSIF_IPMI_BMC
+	tristate "SSIF IPMI BMC driver"
+	depends on I2C && I2C_SLAVE
+	help
+	  This enables the IPMI SMBus system interface (SSIF) at the
+	  management (BMC) side.
+
+	  The driver implements the BMC side of the SMBus system
+	  interface (SSIF).
+
 config IPMB_DEVICE_INTERFACE
 	tristate 'IPMB Interface handler'
 	depends on I2C
diff --git a/drivers/char/ipmi/Makefile b/drivers/char/ipmi/Makefile
index 7ce790efad92..cb6138b8ded9 100644
--- a/drivers/char/ipmi/Makefile
+++ b/drivers/char/ipmi/Makefile
@@ -30,3 +30,4 @@ obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
 obj-$(CONFIG_ASPEED_KCS_IPMI_BMC) += kcs_bmc_aspeed.o
 obj-$(CONFIG_NPCM7XX_KCS_IPMI_BMC) += kcs_bmc_npcm7xx.o
 obj-$(CONFIG_IPMB_DEVICE_INTERFACE) += ipmb_dev_int.o
+obj-$(CONFIG_SSIF_IPMI_BMC) += ssif_bmc.o
diff --git a/drivers/char/ipmi/ipmi_kcs_sm.c b/drivers/char/ipmi/ipmi_kcs_sm.c
index efda90dcf5b3..ecfcb50302f6 100644
--- a/drivers/char/ipmi/ipmi_kcs_sm.c
+++ b/drivers/char/ipmi/ipmi_kcs_sm.c
@@ -122,10 +122,10 @@ struct si_sm_data {
 	unsigned long  error0_timeout;
 };
 
-static unsigned int init_kcs_data(struct si_sm_data *kcs,
-				  struct si_sm_io *io)
+static unsigned int init_kcs_data_with_state(struct si_sm_data *kcs,
+				  struct si_sm_io *io, enum kcs_states state)
 {
-	kcs->state = KCS_IDLE;
+	kcs->state = state;
 	kcs->io = io;
 	kcs->write_pos = 0;
 	kcs->write_count = 0;
@@ -140,6 +140,12 @@ static unsigned int init_kcs_data(struct si_sm_data *kcs,
 	return 2;
 }
 
+static unsigned int init_kcs_data(struct si_sm_data *kcs,
+				  struct si_sm_io *io)
+{
+	return init_kcs_data_with_state(kcs, io, KCS_IDLE);
+}
+
 static inline unsigned char read_status(struct si_sm_data *kcs)
 {
 	return kcs->io->inputb(kcs->io, 1);
@@ -270,7 +276,7 @@ static int start_kcs_transaction(struct si_sm_data *kcs, unsigned char *data,
 	if (size > MAX_KCS_WRITE_SIZE)
 		return IPMI_REQ_LEN_EXCEEDED_ERR;
 
-	if ((kcs->state != KCS_IDLE) && (kcs->state != KCS_HOSED)) {
+	if (kcs->state != KCS_IDLE) {
 		dev_warn(kcs->io->dev, "KCS in invalid state %d\n", kcs->state);
 		return IPMI_NOT_IN_MY_STATE_ERR;
 	}
@@ -495,7 +501,7 @@ static enum si_sm_result kcs_event(struct si_sm_data *kcs, long time)
 	}
 
 	if (kcs->state == KCS_HOSED) {
-		init_kcs_data(kcs, kcs->io);
+		init_kcs_data_with_state(kcs, kcs->io, KCS_ERROR0);
 		return SI_SM_HOSED;
 	}
 
diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 49a1707693c9..186f1fee7534 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -614,7 +614,7 @@ static int __ipmi_bmc_register(struct ipmi_smi *intf,
 static int __scan_channels(struct ipmi_smi *intf, struct ipmi_device_id *id);
 
 
-/**
+/*
  * The driver model view of the IPMI messaging driver.
  */
 static struct platform_driver ipmidriver = {
@@ -1330,6 +1330,7 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
 	unsigned long    flags;
 	struct cmd_rcvr  *rcvr;
 	struct cmd_rcvr  *rcvrs = NULL;
+	struct module    *owner;
 
 	if (!acquire_ipmi_user(user, &i)) {
 		/*
@@ -1392,8 +1393,9 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
 		kfree(rcvr);
 	}
 
+	owner = intf->owner;
 	kref_put(&intf->refcount, intf_free);
-	module_put(intf->owner);
+	module_put(owner);
 }
 
 int ipmi_destroy_user(struct ipmi_user *user)
@@ -3704,12 +3706,16 @@ static void deliver_smi_err_response(struct ipmi_smi *intf,
 				     struct ipmi_smi_msg *msg,
 				     unsigned char err)
 {
+	int rv;
 	msg->rsp[0] = msg->data[0] | 4;
 	msg->rsp[1] = msg->data[1];
 	msg->rsp[2] = err;
 	msg->rsp_size = 3;
-	/* It's an error, so it will never requeue, no need to check return. */
-	handle_one_recv_msg(intf, msg);
+
+	/* This will never requeue, but it may ask us to free the message. */
+	rv = handle_one_recv_msg(intf, msg);
+	if (rv == 0)
+		ipmi_free_smi_msg(msg);
 }
 
 static void cleanup_smi_msgs(struct ipmi_smi *intf)
diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index 6e357ad76f2e..abddd7e43a9a 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -2153,6 +2153,20 @@ skip_fallback_noirq:
 }
 module_init(init_ipmi_si);
 
+static void wait_msg_processed(struct smi_info *smi_info)
+{
+	unsigned long jiffies_now;
+	long time_diff;
+
+	while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) {
+		jiffies_now = jiffies;
+		time_diff = (((long)jiffies_now - (long)smi_info->last_timeout_jiffies)
+		     * SI_USEC_PER_JIFFY);
+		smi_event_handler(smi_info, time_diff);
+		schedule_timeout_uninterruptible(1);
+	}
+}
+
 static void shutdown_smi(void *send_info)
 {
 	struct smi_info *smi_info = send_info;
@@ -2187,16 +2201,13 @@ static void shutdown_smi(void *send_info)
 	 * in the BMC.  Note that timers and CPU interrupts are off,
 	 * so no need for locks.
 	 */
-	while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) {
-		poll(smi_info);
-		schedule_timeout_uninterruptible(1);
-	}
+	wait_msg_processed(smi_info);
+
 	if (smi_info->handlers)
 		disable_si_irq(smi_info);
-	while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) {
-		poll(smi_info);
-		schedule_timeout_uninterruptible(1);
-	}
+
+	wait_msg_processed(smi_info);
+
 	if (smi_info->handlers)
 		smi_info->handlers->cleanup(smi_info->si_sm);
 
diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
index e1072809fe31..4bfd1e306616 100644
--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -74,7 +74,7 @@
 /*
  * Timer values
  */
-#define SSIF_MSG_USEC		20000	/* 20ms between message tries. */
+#define SSIF_MSG_USEC		60000	/* 60ms between message tries. */
 #define SSIF_MSG_PART_USEC	5000	/* 5ms for a message part */
 
 /* How many times to we retry sending/receiving the message. */
diff --git a/drivers/char/ipmi/ipmi_watchdog.c b/drivers/char/ipmi/ipmi_watchdog.c
index 5b4e677929ca..0d4a8dcacfd4 100644
--- a/drivers/char/ipmi/ipmi_watchdog.c
+++ b/drivers/char/ipmi/ipmi_watchdog.c
@@ -23,6 +23,7 @@
 #include <linux/init.h>
 #include <linux/completion.h>
 #include <linux/kdebug.h>
+#include <linux/kstrtox.h>
 #include <linux/rwsem.h>
 #include <linux/errno.h>
 #include <linux/uaccess.h>
@@ -212,8 +213,7 @@ static int set_param_str(const char *val, const struct kernel_param *kp)
 	char       valcp[16];
 	char       *s;
 
-	strncpy(valcp, val, 15);
-	valcp[15] = '\0';
+	strscpy(valcp, val, 16);
 
 	s = strstrip(valcp);
 
diff --git a/drivers/char/ipmi/kcs_bmc_aspeed.c b/drivers/char/ipmi/kcs_bmc_aspeed.c
index 19c32bf50e0e..2dea8cd5a09a 100644
--- a/drivers/char/ipmi/kcs_bmc_aspeed.c
+++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
@@ -406,13 +406,31 @@ static void aspeed_kcs_check_obe(struct timer_list *timer)
 static void aspeed_kcs_irq_mask_update(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 state)
 {
 	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
+	int rc;
+	u8 str;
 
 	/* We don't have an OBE IRQ, emulate it */
 	if (mask & KCS_BMC_EVENT_TYPE_OBE) {
-		if (KCS_BMC_EVENT_TYPE_OBE & state)
-			mod_timer(&priv->obe.timer, jiffies + OBE_POLL_PERIOD);
-		else
+		if (KCS_BMC_EVENT_TYPE_OBE & state) {
+			/*
+			 * Given we don't have an OBE IRQ, delay by polling briefly to see if we can
+			 * observe such an event before returning to the caller. This is not
+			 * incorrect because OBF may have already become clear before enabling the
+			 * IRQ if we had one, under which circumstance no event will be propagated
+			 * anyway.
+			 *
+			 * The onus is on the client to perform a race-free check that it hasn't
+			 * missed the event.
+			 */
+			rc = read_poll_timeout_atomic(aspeed_kcs_inb, str,
+						      !(str & KCS_BMC_STR_OBF), 1, 100, false,
+						      &priv->kcs_bmc, priv->kcs_bmc.ioreg.str);
+			/* Time for the slow path? */
+			if (rc == -ETIMEDOUT)
+				mod_timer(&priv->obe.timer, jiffies + OBE_POLL_PERIOD);
+		} else {
 			del_timer(&priv->obe.timer);
+		}
 	}
 
 	if (mask & KCS_BMC_EVENT_TYPE_IBF) {
diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
new file mode 100644
index 000000000000..caee848261e9
--- /dev/null
+++ b/drivers/char/ipmi/ssif_bmc.c
@@ -0,0 +1,873 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * The driver for BMC side of SSIF interface
+ *
+ * Copyright (c) 2022, Ampere Computing LLC
+ *
+ */
+
+#include <linux/i2c.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+#include <linux/jiffies.h>
+#include <linux/ipmi_ssif_bmc.h>
+
+#define DEVICE_NAME                             "ipmi-ssif-host"
+
+#define GET_8BIT_ADDR(addr_7bit)                (((addr_7bit) << 1) & 0xff)
+
+/* A standard SMBus Transaction is limited to 32 data bytes */
+#define MAX_PAYLOAD_PER_TRANSACTION             32
+/* Transaction includes the address, the command, the length and the PEC byte */
+#define MAX_TRANSACTION                         (MAX_PAYLOAD_PER_TRANSACTION + 4)
+
+#define MAX_IPMI_DATA_PER_START_TRANSACTION     30
+#define MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION    31
+
+#define SSIF_IPMI_SINGLEPART_WRITE              0x2
+#define SSIF_IPMI_SINGLEPART_READ               0x3
+#define SSIF_IPMI_MULTIPART_WRITE_START         0x6
+#define SSIF_IPMI_MULTIPART_WRITE_MIDDLE        0x7
+#define SSIF_IPMI_MULTIPART_WRITE_END           0x8
+#define SSIF_IPMI_MULTIPART_READ_START          0x3
+#define SSIF_IPMI_MULTIPART_READ_MIDDLE         0x9
+
+/*
+ * IPMI 2.0 Spec, section 12.7 SSIF Timing,
+ * Request-to-Response Time is T6max(250ms) - T1max(20ms) - 3ms = 227ms
+ * Recover ssif_bmc from busy state if it takes up to 500ms
+ */
+#define RESPONSE_TIMEOUT                        500 /* ms */
+
+struct ssif_part_buffer {
+	u8 address;
+	u8 smbus_cmd;
+	u8 length;
+	u8 payload[MAX_PAYLOAD_PER_TRANSACTION];
+	u8 pec;
+	u8 index;
+};
+
+/*
+ * SSIF internal states:
+ *   SSIF_READY         0x00 : Ready state
+ *   SSIF_START         0x01 : Start smbus transaction
+ *   SSIF_SMBUS_CMD     0x02 : Received SMBus command
+ *   SSIF_REQ_RECVING   0x03 : Receiving request
+ *   SSIF_RES_SENDING   0x04 : Sending response
+ *   SSIF_ABORTING      0x05 : Aborting state
+ */
+enum ssif_state {
+	SSIF_READY,
+	SSIF_START,
+	SSIF_SMBUS_CMD,
+	SSIF_REQ_RECVING,
+	SSIF_RES_SENDING,
+	SSIF_ABORTING,
+	SSIF_STATE_MAX
+};
+
+struct ssif_bmc_ctx {
+	struct i2c_client       *client;
+	struct miscdevice       miscdev;
+	int                     msg_idx;
+	bool                    pec_support;
+	/* ssif bmc spinlock */
+	spinlock_t              lock;
+	wait_queue_head_t       wait_queue;
+	u8                      running;
+	enum ssif_state         state;
+	/* Timeout waiting for response */
+	struct timer_list       response_timer;
+	bool                    response_timer_inited;
+	/* Flag to identify a Multi-part Read Transaction */
+	bool                    is_singlepart_read;
+	u8                      nbytes_processed;
+	u8                      remain_len;
+	u8                      recv_len;
+	/* Block Number of a Multi-part Read Transaction */
+	u8                      block_num;
+	bool                    request_available;
+	bool                    response_in_progress;
+	bool                    busy;
+	bool                    aborting;
+	/* Buffer for SSIF Transaction part*/
+	struct ssif_part_buffer part_buf;
+	struct ipmi_ssif_msg    response;
+	struct ipmi_ssif_msg    request;
+};
+
+static inline struct ssif_bmc_ctx *to_ssif_bmc(struct file *file)
+{
+	return container_of(file->private_data, struct ssif_bmc_ctx, miscdev);
+}
+
+static const char *state_to_string(enum ssif_state state)
+{
+	switch (state) {
+	case SSIF_READY:
+		return "SSIF_READY";
+	case SSIF_START:
+		return "SSIF_START";
+	case SSIF_SMBUS_CMD:
+		return "SSIF_SMBUS_CMD";
+	case SSIF_REQ_RECVING:
+		return "SSIF_REQ_RECVING";
+	case SSIF_RES_SENDING:
+		return "SSIF_RES_SENDING";
+	case SSIF_ABORTING:
+		return "SSIF_ABORTING";
+	default:
+		return "SSIF_STATE_UNKNOWN";
+	}
+}
+
+/* Handle SSIF message that will be sent to user */
+static ssize_t ssif_bmc_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	struct ipmi_ssif_msg msg;
+	unsigned long flags;
+	ssize_t ret;
+
+	spin_lock_irqsave(&ssif_bmc->lock, flags);
+	while (!ssif_bmc->request_available) {
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		ret = wait_event_interruptible(ssif_bmc->wait_queue,
+					       ssif_bmc->request_available);
+		if (ret)
+			return ret;
+		spin_lock_irqsave(&ssif_bmc->lock, flags);
+	}
+
+	if (count < min_t(ssize_t,
+			  sizeof_field(struct ipmi_ssif_msg, len) + ssif_bmc->request.len,
+			  sizeof(struct ipmi_ssif_msg))) {
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+		ret = -EINVAL;
+	} else {
+		count = min_t(ssize_t,
+			      sizeof_field(struct ipmi_ssif_msg, len) + ssif_bmc->request.len,
+			      sizeof(struct ipmi_ssif_msg));
+		memcpy(&msg, &ssif_bmc->request, count);
+		ssif_bmc->request_available = false;
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+		ret = copy_to_user(buf, &msg, count);
+	}
+
+	return (ret < 0) ? ret : count;
+}
+
+/* Handle SSIF message that is written by user */
+static ssize_t ssif_bmc_write(struct file *file, const char __user *buf, size_t count,
+			      loff_t *ppos)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	struct ipmi_ssif_msg msg;
+	unsigned long flags;
+	ssize_t ret;
+
+	if (count > sizeof(struct ipmi_ssif_msg))
+		return -EINVAL;
+
+	if (copy_from_user(&msg, buf, count))
+		return -EFAULT;
+
+	if (!msg.len || count < sizeof_field(struct ipmi_ssif_msg, len) + msg.len)
+		return -EINVAL;
+
+	spin_lock_irqsave(&ssif_bmc->lock, flags);
+	while (ssif_bmc->response_in_progress) {
+		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		ret = wait_event_interruptible(ssif_bmc->wait_queue,
+					       !ssif_bmc->response_in_progress);
+		if (ret)
+			return ret;
+		spin_lock_irqsave(&ssif_bmc->lock, flags);
+	}
+
+	/*
+	 * The write must complete before the response timeout fired, otherwise
+	 * the response is aborted and wait for next request
+	 * Return -EINVAL if the response is aborted
+	 */
+	ret = (ssif_bmc->response_timer_inited) ? 0 : -EINVAL;
+	if (ret)
+		goto exit;
+
+	del_timer(&ssif_bmc->response_timer);
+	ssif_bmc->response_timer_inited = false;
+
+	memcpy(&ssif_bmc->response, &msg, count);
+	ssif_bmc->is_singlepart_read = (msg.len <= MAX_PAYLOAD_PER_TRANSACTION);
+
+	ssif_bmc->response_in_progress = true;
+
+	/* ssif_bmc not busy */
+	ssif_bmc->busy = false;
+
+	/* Clean old request buffer */
+	memset(&ssif_bmc->request, 0, sizeof(struct ipmi_ssif_msg));
+exit:
+	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+	return (ret < 0) ? ret : count;
+}
+
+static int ssif_bmc_open(struct inode *inode, struct file *file)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	int ret = 0;
+
+	spin_lock_irq(&ssif_bmc->lock);
+	if (!ssif_bmc->running)
+		ssif_bmc->running = 1;
+	else
+		ret = -EBUSY;
+	spin_unlock_irq(&ssif_bmc->lock);
+
+	return ret;
+}
+
+static __poll_t ssif_bmc_poll(struct file *file, poll_table *wait)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+	__poll_t mask = 0;
+
+	poll_wait(file, &ssif_bmc->wait_queue, wait);
+
+	spin_lock_irq(&ssif_bmc->lock);
+	/* The request is available, userspace application can get the request */
+	if (ssif_bmc->request_available)
+		mask |= EPOLLIN;
+
+	spin_unlock_irq(&ssif_bmc->lock);
+
+	return mask;
+}
+
+static int ssif_bmc_release(struct inode *inode, struct file *file)
+{
+	struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+
+	spin_lock_irq(&ssif_bmc->lock);
+	ssif_bmc->running = 0;
+	spin_unlock_irq(&ssif_bmc->lock);
+
+	return 0;
+}
+
+/*
+ * System calls to device interface for user apps
+ */
+static const struct file_operations ssif_bmc_fops = {
+	.owner		= THIS_MODULE,
+	.open		= ssif_bmc_open,
+	.read		= ssif_bmc_read,
+	.write		= ssif_bmc_write,
+	.release	= ssif_bmc_release,
+	.poll		= ssif_bmc_poll,
+};
+
+/* Called with ssif_bmc->lock held. */
+static void complete_response(struct ssif_bmc_ctx *ssif_bmc)
+{
+	/* Invalidate response in buffer to denote it having been sent. */
+	ssif_bmc->response.len = 0;
+	ssif_bmc->response_in_progress = false;
+	ssif_bmc->nbytes_processed = 0;
+	ssif_bmc->remain_len = 0;
+	ssif_bmc->busy = false;
+	memset(&ssif_bmc->part_buf, 0, sizeof(struct ssif_part_buffer));
+	wake_up_all(&ssif_bmc->wait_queue);
+}
+
+static void response_timeout(struct timer_list *t)
+{
+	struct ssif_bmc_ctx *ssif_bmc = from_timer(ssif_bmc, t, response_timer);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ssif_bmc->lock, flags);
+
+	/* Do nothing if the response is in progress */
+	if (!ssif_bmc->response_in_progress) {
+		/* Recover ssif_bmc from busy */
+		ssif_bmc->busy = false;
+		ssif_bmc->response_timer_inited = false;
+		/* Set aborting flag */
+		ssif_bmc->aborting = true;
+	}
+
+	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+}
+
+/* Called with ssif_bmc->lock held. */
+static void handle_request(struct ssif_bmc_ctx *ssif_bmc)
+{
+	/* set ssif_bmc to busy waiting for response */
+	ssif_bmc->busy = true;
+	/* Request message is available to process */
+	ssif_bmc->request_available = true;
+	/* Clean old response buffer */
+	memset(&ssif_bmc->response, 0, sizeof(struct ipmi_ssif_msg));
+	/* This is the new READ request.*/
+	wake_up_all(&ssif_bmc->wait_queue);
+
+	/* Armed timer to recover slave from busy state in case of no response */
+	if (!ssif_bmc->response_timer_inited) {
+		timer_setup(&ssif_bmc->response_timer, response_timeout, 0);
+		ssif_bmc->response_timer_inited = true;
+	}
+	mod_timer(&ssif_bmc->response_timer, jiffies + msecs_to_jiffies(RESPONSE_TIMEOUT));
+}
+
+static void calculate_response_part_pec(struct ssif_part_buffer *part)
+{
+	u8 addr = part->address;
+
+	/* PEC - Start Read Address */
+	part->pec = i2c_smbus_pec(0, &addr, 1);
+	/* PEC - SSIF Command */
+	part->pec = i2c_smbus_pec(part->pec, &part->smbus_cmd, 1);
+	/* PEC - Restart Write Address */
+	addr = addr | 0x01;
+	part->pec = i2c_smbus_pec(part->pec, &addr, 1);
+	part->pec = i2c_smbus_pec(part->pec, &part->length, 1);
+	if (part->length)
+		part->pec = i2c_smbus_pec(part->pec, part->payload, part->length);
+}
+
+static void set_singlepart_response_buffer(struct ssif_bmc_ctx *ssif_bmc)
+{
+	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
+
+	part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
+	part->length = (u8)ssif_bmc->response.len;
+
+	/* Clear the rest to 0 */
+	memset(part->payload + part->length, 0, MAX_PAYLOAD_PER_TRANSACTION - part->length);
+	memcpy(&part->payload[0], &ssif_bmc->response.payload[0], part->length);
+}
+
+static void set_multipart_response_buffer(struct ssif_bmc_ctx *ssif_bmc)
+{
+	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
+	u8 part_len = 0;
+
+	part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
+	switch (part->smbus_cmd) {
+	case SSIF_IPMI_MULTIPART_READ_START:
+		/*
+		 * Read Start length is 32 bytes.
+		 * Read Start transfer first 30 bytes of IPMI response
+		 * and 2 special code 0x00, 0x01.
+		 */
+		ssif_bmc->nbytes_processed = 0;
+		ssif_bmc->block_num = 0;
+		part->length = MAX_PAYLOAD_PER_TRANSACTION;
+		part_len = MAX_IPMI_DATA_PER_START_TRANSACTION;
+		ssif_bmc->remain_len = ssif_bmc->response.len - part_len;
+
+		part->payload[0] = 0x00; /* Start Flag */
+		part->payload[1] = 0x01; /* Start Flag */
+
+		memcpy(&part->payload[2], &ssif_bmc->response.payload[0], part_len);
+		break;
+
+	case SSIF_IPMI_MULTIPART_READ_MIDDLE:
+		/*
+		 * IPMI READ Middle or READ End messages can carry up to 31 bytes
+		 * IPMI data plus block number byte.
+		 */
+		if (ssif_bmc->remain_len <= MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION) {
+			/*
+			 * This is READ End message
+			 *  Return length is the remaining response data length
+			 *  plus block number
+			 *  Block number 0xFF is to indicate this is last message
+			 *
+			 */
+			/* Clean the buffer */
+			memset(&part->payload[0], 0, MAX_PAYLOAD_PER_TRANSACTION);
+			part->length = ssif_bmc->remain_len + 1;
+			part_len = ssif_bmc->remain_len;
+			ssif_bmc->block_num = 0xFF;
+			part->payload[0] = ssif_bmc->block_num;
+		} else {
+			/*
+			 * This is READ Middle message
+			 *  Response length is the maximum SMBUS transfer length
+			 *  Block number byte is incremented
+			 * Return length is maximum SMBUS transfer length
+			 */
+			part->length = MAX_PAYLOAD_PER_TRANSACTION;
+			part_len = MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
+			part->payload[0] = ssif_bmc->block_num;
+			ssif_bmc->block_num++;
+		}
+
+		ssif_bmc->remain_len -= part_len;
+		memcpy(&part->payload[1], ssif_bmc->response.payload + ssif_bmc->nbytes_processed,
+		       part_len);
+		break;
+
+	default:
+		/* Do not expect to go to this case */
+		dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x\n",
+			__func__, part->smbus_cmd);
+		break;
+	}
+
+	ssif_bmc->nbytes_processed += part_len;
+}
+
+static bool supported_read_cmd(u8 cmd)
+{
+	if (cmd == SSIF_IPMI_SINGLEPART_READ ||
+	    cmd == SSIF_IPMI_MULTIPART_READ_START ||
+	    cmd == SSIF_IPMI_MULTIPART_READ_MIDDLE)
+		return true;
+
+	return false;
+}
+
+static bool supported_write_cmd(u8 cmd)
+{
+	if (cmd == SSIF_IPMI_SINGLEPART_WRITE ||
+	    cmd == SSIF_IPMI_MULTIPART_WRITE_START ||
+	    cmd == SSIF_IPMI_MULTIPART_WRITE_MIDDLE ||
+	    cmd == SSIF_IPMI_MULTIPART_WRITE_END)
+		return true;
+
+	return false;
+}
+
+/* Process the IPMI response that will be read by master */
+static void handle_read_processed(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
+
+	/* msg_idx start from 0 */
+	if (part->index < part->length)
+		*val = part->payload[part->index];
+	else if (part->index == part->length && ssif_bmc->pec_support)
+		*val = part->pec;
+	else
+		*val = 0;
+
+	part->index++;
+}
+
+static void handle_write_received(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	/*
+	 * The msg_idx must be 1 when first enter SSIF_REQ_RECVING state
+	 * And it would never exceeded 36 bytes included the 32 bytes max payload +
+	 * the address + the command + the len and the PEC.
+	 */
+	if (ssif_bmc->msg_idx < 1  || ssif_bmc->msg_idx > MAX_TRANSACTION)
+		return;
+
+	if (ssif_bmc->msg_idx == 1) {
+		ssif_bmc->part_buf.length = *val;
+		ssif_bmc->part_buf.index = 0;
+	} else {
+		ssif_bmc->part_buf.payload[ssif_bmc->part_buf.index++] = *val;
+	}
+
+	ssif_bmc->msg_idx++;
+}
+
+static bool validate_request_part(struct ssif_bmc_ctx *ssif_bmc)
+{
+	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
+	bool ret = true;
+	u8 cpec;
+	u8 addr;
+
+	if (part->index == part->length) {
+		/* PEC is not included */
+		ssif_bmc->pec_support = false;
+		ret = true;
+		goto exit;
+	}
+
+	if (part->index != part->length + 1) {
+		ret = false;
+		goto exit;
+	}
+
+	/* PEC is included */
+	ssif_bmc->pec_support = true;
+	part->pec = part->payload[part->length];
+	addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
+	cpec = i2c_smbus_pec(0, &addr, 1);
+	cpec = i2c_smbus_pec(cpec, &part->smbus_cmd, 1);
+	cpec = i2c_smbus_pec(cpec, &part->length, 1);
+	/*
+	 * As SMBus specification does not allow the length
+	 * (byte count) in the Write-Block protocol to be zero.
+	 * Therefore, it is illegal to have the last Middle
+	 * transaction in the sequence carry 32-byte and have
+	 * a length of ‘0’ in the End transaction.
+	 * But some users may try to use this way and we should
+	 * prevent ssif_bmc driver broken in this case.
+	 */
+	if (part->length)
+		cpec = i2c_smbus_pec(cpec, part->payload, part->length);
+
+	if (cpec != part->pec)
+		ret = false;
+
+exit:
+	return ret;
+}
+
+static void process_request_part(struct ssif_bmc_ctx *ssif_bmc)
+{
+	struct ssif_part_buffer *part = &ssif_bmc->part_buf;
+	unsigned int len;
+
+	switch (part->smbus_cmd) {
+	case SSIF_IPMI_SINGLEPART_WRITE:
+		/* save the whole part to request*/
+		ssif_bmc->request.len = part->length;
+		memcpy(ssif_bmc->request.payload, part->payload, part->length);
+
+		break;
+	case SSIF_IPMI_MULTIPART_WRITE_START:
+		ssif_bmc->request.len = 0;
+
+		fallthrough;
+	case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
+	case SSIF_IPMI_MULTIPART_WRITE_END:
+		len = ssif_bmc->request.len + part->length;
+		/* Do the bound check here, not allow the request len exceed 254 bytes */
+		if (len > IPMI_SSIF_PAYLOAD_MAX) {
+			dev_warn(&ssif_bmc->client->dev,
+				 "Warn: Request exceeded 254 bytes, aborting");
+			/* Request too long, aborting */
+			ssif_bmc->aborting =  true;
+		} else {
+			memcpy(ssif_bmc->request.payload + ssif_bmc->request.len,
+			       part->payload, part->length);
+			ssif_bmc->request.len += part->length;
+		}
+		break;
+	default:
+		/* Do not expect to go to this case */
+		dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x\n",
+			__func__, part->smbus_cmd);
+		break;
+	}
+}
+
+static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	/* SMBUS command can vary (single or multi-part) */
+	ssif_bmc->part_buf.smbus_cmd = *val;
+	ssif_bmc->msg_idx = 1;
+	memset(&ssif_bmc->part_buf.payload[0], 0, MAX_PAYLOAD_PER_TRANSACTION);
+
+	if (*val == SSIF_IPMI_SINGLEPART_WRITE || *val == SSIF_IPMI_MULTIPART_WRITE_START) {
+		/*
+		 * The response maybe not come in-time, causing host SSIF driver
+		 * to timeout and resend a new request. In such case check for
+		 * pending response and clear it
+		 */
+		if (ssif_bmc->response_in_progress)
+			complete_response(ssif_bmc);
+
+		/* This is new request, flip aborting flag if set */
+		if (ssif_bmc->aborting)
+			ssif_bmc->aborting = false;
+	}
+}
+
+static void on_read_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY ||
+	    ssif_bmc->state == SSIF_START ||
+	    ssif_bmc->state == SSIF_REQ_RECVING ||
+	    ssif_bmc->state == SSIF_RES_SENDING) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected READ REQUESTED in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_ABORTING;
+		*val = 0;
+		return;
+
+	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
+		if (!supported_read_cmd(ssif_bmc->part_buf.smbus_cmd)) {
+			dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus read command=0x%x",
+				 ssif_bmc->part_buf.smbus_cmd);
+			ssif_bmc->aborting = true;
+		}
+
+		if (ssif_bmc->aborting)
+			ssif_bmc->state = SSIF_ABORTING;
+		else
+			ssif_bmc->state = SSIF_RES_SENDING;
+	}
+
+	ssif_bmc->msg_idx = 0;
+
+	/* Send 0 if there is nothing to send */
+	if (!ssif_bmc->response_in_progress || ssif_bmc->state == SSIF_ABORTING) {
+		*val = 0;
+		return;
+	}
+
+	if (ssif_bmc->is_singlepart_read)
+		set_singlepart_response_buffer(ssif_bmc);
+	else
+		set_multipart_response_buffer(ssif_bmc);
+
+	calculate_response_part_pec(&ssif_bmc->part_buf);
+	ssif_bmc->part_buf.index = 0;
+	*val = ssif_bmc->part_buf.length;
+}
+
+static void on_read_processed_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY ||
+	    ssif_bmc->state == SSIF_START ||
+	    ssif_bmc->state == SSIF_REQ_RECVING ||
+	    ssif_bmc->state == SSIF_SMBUS_CMD) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected READ PROCESSED in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_ABORTING;
+		*val = 0;
+		return;
+	}
+
+	/* Send 0 if there is nothing to send */
+	if (!ssif_bmc->response_in_progress || ssif_bmc->state == SSIF_ABORTING) {
+		*val = 0;
+		return;
+	}
+
+	handle_read_processed(ssif_bmc, val);
+}
+
+static void on_write_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY || ssif_bmc->state == SSIF_SMBUS_CMD) {
+		ssif_bmc->state = SSIF_START;
+
+	} else if (ssif_bmc->state == SSIF_START ||
+		   ssif_bmc->state == SSIF_REQ_RECVING ||
+		   ssif_bmc->state == SSIF_RES_SENDING) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected WRITE REQUEST in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_ABORTING;
+		return;
+	}
+
+	ssif_bmc->msg_idx = 0;
+	ssif_bmc->part_buf.address = *val;
+}
+
+static void on_write_received_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY ||
+	    ssif_bmc->state == SSIF_RES_SENDING) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected WRITE RECEIVED in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_ABORTING;
+
+	} else if (ssif_bmc->state == SSIF_START) {
+		ssif_bmc->state = SSIF_SMBUS_CMD;
+
+	} else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
+		if (!supported_write_cmd(ssif_bmc->part_buf.smbus_cmd)) {
+			dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus write command=0x%x",
+				 ssif_bmc->part_buf.smbus_cmd);
+			ssif_bmc->aborting = true;
+		}
+
+		if (ssif_bmc->aborting)
+			ssif_bmc->state = SSIF_ABORTING;
+		else
+			ssif_bmc->state = SSIF_REQ_RECVING;
+	}
+
+	/* This is response sending state */
+	if (ssif_bmc->state == SSIF_REQ_RECVING)
+		handle_write_received(ssif_bmc, val);
+	else if (ssif_bmc->state == SSIF_SMBUS_CMD)
+		process_smbus_cmd(ssif_bmc, val);
+}
+
+static void on_stop_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+	if (ssif_bmc->state == SSIF_READY ||
+	    ssif_bmc->state == SSIF_START ||
+	    ssif_bmc->state == SSIF_SMBUS_CMD ||
+	    ssif_bmc->state == SSIF_ABORTING) {
+		dev_warn(&ssif_bmc->client->dev,
+			 "Warn: %s unexpected SLAVE STOP in state=%s\n",
+			 __func__, state_to_string(ssif_bmc->state));
+		ssif_bmc->state = SSIF_READY;
+
+	} else if (ssif_bmc->state == SSIF_REQ_RECVING) {
+		if (validate_request_part(ssif_bmc)) {
+			process_request_part(ssif_bmc);
+			if (ssif_bmc->part_buf.smbus_cmd == SSIF_IPMI_SINGLEPART_WRITE ||
+			    ssif_bmc->part_buf.smbus_cmd == SSIF_IPMI_MULTIPART_WRITE_END)
+				handle_request(ssif_bmc);
+			ssif_bmc->state = SSIF_READY;
+		} else {
+			/*
+			 * A BMC that receives an invalid request drop the data for the write
+			 * transaction and any further transactions (read or write) until
+			 * the next valid read or write Start transaction is received
+			 */
+			dev_err(&ssif_bmc->client->dev, "Error: invalid pec\n");
+			ssif_bmc->aborting = true;
+		}
+	} else if (ssif_bmc->state == SSIF_RES_SENDING) {
+		if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num == 0xFF)
+			/* Invalidate response buffer to denote it is sent */
+			complete_response(ssif_bmc);
+		ssif_bmc->state = SSIF_READY;
+	}
+
+	/* Reset message index */
+	ssif_bmc->msg_idx = 0;
+}
+
+/*
+ * Callback function to handle I2C slave events
+ */
+static int ssif_bmc_cb(struct i2c_client *client, enum i2c_slave_event event, u8 *val)
+{
+	unsigned long flags;
+	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
+	int ret = 0;
+
+	spin_lock_irqsave(&ssif_bmc->lock, flags);
+
+	switch (event) {
+	case I2C_SLAVE_READ_REQUESTED:
+		on_read_requested_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_WRITE_REQUESTED:
+		on_write_requested_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_READ_PROCESSED:
+		on_read_processed_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_WRITE_RECEIVED:
+		on_write_received_event(ssif_bmc, val);
+		break;
+
+	case I2C_SLAVE_STOP:
+		on_stop_event(ssif_bmc, val);
+		break;
+
+	default:
+		dev_warn(&ssif_bmc->client->dev, "Warn: Unknown i2c slave event\n");
+		break;
+	}
+
+	if (!ssif_bmc->aborting && ssif_bmc->busy)
+		ret = -EBUSY;
+
+	spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+	return ret;
+}
+
+static int ssif_bmc_probe(struct i2c_client *client)
+{
+	struct ssif_bmc_ctx *ssif_bmc;
+	int ret;
+
+	ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc), GFP_KERNEL);
+	if (!ssif_bmc)
+		return -ENOMEM;
+
+	spin_lock_init(&ssif_bmc->lock);
+
+	init_waitqueue_head(&ssif_bmc->wait_queue);
+	ssif_bmc->request_available = false;
+	ssif_bmc->response_in_progress = false;
+	ssif_bmc->busy = false;
+	ssif_bmc->response_timer_inited = false;
+
+	/* Register misc device interface */
+	ssif_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
+	ssif_bmc->miscdev.name = DEVICE_NAME;
+	ssif_bmc->miscdev.fops = &ssif_bmc_fops;
+	ssif_bmc->miscdev.parent = &client->dev;
+	ret = misc_register(&ssif_bmc->miscdev);
+	if (ret)
+		return ret;
+
+	ssif_bmc->client = client;
+	ssif_bmc->client->flags |= I2C_CLIENT_SLAVE;
+
+	/* Register I2C slave */
+	i2c_set_clientdata(client, ssif_bmc);
+	ret = i2c_slave_register(client, ssif_bmc_cb);
+	if (ret)
+		misc_deregister(&ssif_bmc->miscdev);
+
+	return ret;
+}
+
+static void ssif_bmc_remove(struct i2c_client *client)
+{
+	struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
+
+	i2c_slave_unregister(client);
+	misc_deregister(&ssif_bmc->miscdev);
+}
+
+static const struct of_device_id ssif_bmc_match[] = {
+	{ .compatible = "ssif-bmc" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ssif_bmc_match);
+
+static const struct i2c_device_id ssif_bmc_id[] = {
+	{ DEVICE_NAME, 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, ssif_bmc_id);
+
+static struct i2c_driver ssif_bmc_driver = {
+	.driver         = {
+		.name           = DEVICE_NAME,
+		.of_match_table = ssif_bmc_match,
+	},
+	.probe_new      = ssif_bmc_probe,
+	.remove         = ssif_bmc_remove,
+	.id_table       = ssif_bmc_id,
+};
+
+module_i2c_driver(ssif_bmc_driver);
+
+MODULE_AUTHOR("Quan Nguyen <quan@os.amperecomputing.com>");
+MODULE_AUTHOR("Chuong Tran <chuong@os.amperecomputing.com>");
+MODULE_DESCRIPTION("Linux device driver of the BMC IPMI SSIF interface.");
+MODULE_LICENSE("GPL");