[PATCH v6 1/4] ipmi: ssif_bmc: Add SSIF BMC driver

Quan Nguyen
2022-03-10T11:42:03Z

The SMBus system interface (SSIF) IPMI BMC driver can be used to perform
in-band IPMI communication with their host in management (BMC) side.

Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
---
v6:
+ Drop the use of slave_enable() [Wolfram]
+ Make i2c-aspeed to issue RxCmdLast command on all
I2C_SLAVE_WRITE_REQUESTED event to assert NAK when slave busy [Quan]
+ Make i2c slave to return -EBUSY when it's busy [Quan]
+ Drop the aborting feature as return Completion Code 0xFF may stop
host to retry and make ipmi_ssif.so fails to load [Quan]
+ Add timer to recover slave from busy state when no response [Quan]
+ Clean request/response buffer appropriately [Quan]
+ Add some minor change on error and warning messages [Quan]

v5:
+ None

v4:
+ Send response with Completion code 0xFF when aborting [Quan]
+ Added bounding check on SMBus writes and the whole request [Dan]
+ Moved buffer to end of struct ssif_bmc_ctx to avoid context
corruption if somehow buffer is written past the end [Dan]
+ Return -EINVAL if userspace buffer too small, dont
silence truncate [Corey, Joel]
+ Not necessary to check NONBLOCK in lock [Corey]
+ Enforce one user at a time [Joel]
+ Reject write with invalid response length from userspace [Corey]
+ Add state machines for better ssif bmc state handling [Quan]
+ Drop ssif_bmc_aspeed.c and make ssif_bmc.c is generic
SSIF BMC driver [Quan]
+ Change compatible string "aspeed,ast2500-ssif-bmc" to
"ampere,ssif-bmc" [Quan]
+ Abort current request with invalid SMBus write or
invalid command [Quan]
+ Abort all request if there is pending response [Quan]
+ Changed validate_pec() to validate_request() [Quan]
+ Add unsupported_smbus_cmd() to handle unknown SMBus command [Quan]
+ Print internal state string for ease investigating issue [Quan]
+ Move to READY state on SLAVE_STOP event [Quan]
+ Change initilize_transfer() to process_smbus_cmd() [Quan]
+ Introduce functions for each slave event [Quan]

v3:
+ Removed redundant license info [Joel]
+ Switched to use traditional if-else [Joel]
+ Removed unused ssif_bmc_ioctl() [Joel]
+ Made handle_request()/complete_response() to return void [Joel]
+ Refactored send_ssif_bmc_response() and
receive_ssif_bmc_request() [Corey]
+ Removed mutex [Corey]
+ Use spin_lock/unlock_irqsave/restore in callback [Corey]
+ Removed the unnecessary memset [Corey]
+ Switch to use dev_err() [Corey]

v2:
+ Fixed compiling error with COMPILE_TEST for arc

drivers/char/ipmi/Kconfig | 11 +
drivers/char/ipmi/Makefile | 1 +
drivers/char/ipmi/ssif_bmc.c | 791 +++++++++++++++++++++++++++++++++++
drivers/char/ipmi/ssif_bmc.h | 102 +++++
4 files changed, 905 insertions(+)
create mode 100644 drivers/char/ipmi/ssif_bmc.c
create mode 100644 drivers/char/ipmi/ssif_bmc.h

diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
index b061e6b513ed..18a89093d64e 100644
--- a/drivers/char/ipmi/Kconfig
+++ b/drivers/char/ipmi/Kconfig
@@ -169,6 +169,17 @@ 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"
+ select I2C
+ select 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/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
new file mode 100644
index 000000000000..62db97773654
--- /dev/null
+++ b/drivers/char/ipmi/ssif_bmc.c
@@ -0,0 +1,791 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * 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 "ssif_bmc.h"
+
+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_BAD_SMBUS:
+ return "SSIF_BAD_SMBUS";
+ 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 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, ssif_msg_len(&ssif_bmc->request), sizeof(struct ssif_msg))) {
+ spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+ ret = -EINVAL;
+ } else {
+ count = min_t(ssize_t, ssif_msg_len(&ssif_bmc->request), sizeof(struct 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 ssif_msg msg;
+ unsigned long flags;
+ ssize_t ret;
+
+ if (count > sizeof(struct ssif_msg))
+ return -EINVAL;
+
+ ret = copy_from_user(&msg, buf, count);
+ if (ret)
+ return ret;
+
+ if (!msg.len || count < ssif_msg_len(&msg))
+ 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);
+ }
+
+ memcpy(&ssif_bmc->response, &msg, count);
+ ssif_bmc->is_singlepart_read = (ssif_msg_len(&msg) <= MAX_PAYLOAD_PER_TRANSACTION + 1);
+
+ ssif_bmc->response_in_progress = true;
+
+ /* ssif_bmc not busy */
+ ssif_bmc->busy = false;
+
+ if (ssif_bmc->response_timer_inited) {
+ del_timer(&ssif_bmc->response_timer);
+ ssif_bmc->response_timer_inited = false;
+ }
+ /* Clean old request buffer */
+ memset(&ssif_bmc->request, 0, sizeof(struct ssif_msg));
+
+ spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+ return 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 unsigned int ssif_bmc_poll(struct file *file, poll_table *wait)
+{
+ struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
+ unsigned int 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 |= POLLIN;
+
+ 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->response_buf, 0, MAX_PAYLOAD_PER_TRANSACTION);
+ 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);
+
+ /* Recover ssif_bmc from busy */
+ ssif_bmc->busy = false;
+ del_timer(&ssif_bmc->response_timer);
+ ssif_bmc->response_timer_inited = false;
+
+ 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 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 set_multipart_response_buffer(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+ u8 response_len = 0;
+ int idx = 0;
+ u8 data_len;
+
+ data_len = ssif_bmc->response.len;
+ switch (ssif_bmc->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.
+ */
+ *val = MAX_PAYLOAD_PER_TRANSACTION;
+ ssif_bmc->remain_len = data_len - MAX_IPMI_DATA_PER_START_TRANSACTION;
+ ssif_bmc->block_num = 0;
+
+ ssif_bmc->response_buf[idx++] = 0x00; /* Start Flag */
+ ssif_bmc->response_buf[idx++] = 0x01; /* Start Flag */
+ ssif_bmc->response_buf[idx++] = ssif_bmc->response.netfn_lun;
+ ssif_bmc->response_buf[idx++] = ssif_bmc->response.cmd;
+ ssif_bmc->response_buf[idx++] = ssif_bmc->response.payload[0];
+
+ response_len = MAX_PAYLOAD_PER_TRANSACTION - idx;
+
+ memcpy(&ssif_bmc->response_buf[idx], &ssif_bmc->response.payload[1],
+ response_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
+ *
+ */
+ *val = ssif_bmc->remain_len + 1;
+ ssif_bmc->block_num = 0xFF;
+ ssif_bmc->response_buf[idx++] = ssif_bmc->block_num;
+ response_len = ssif_bmc->remain_len;
+ /* Clean the buffer */
+ memset(&ssif_bmc->response_buf[idx], 0, MAX_PAYLOAD_PER_TRANSACTION - idx);
+ } 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
+ */
+ *val = MAX_PAYLOAD_PER_TRANSACTION;
+ ssif_bmc->remain_len -= MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
+ response_len = MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
+ ssif_bmc->response_buf[idx++] = ssif_bmc->block_num;
+ ssif_bmc->block_num++;
+ }
+
+ memcpy(&ssif_bmc->response_buf[idx],
+ ssif_bmc->response.payload + 1 + ssif_bmc->nbytes_processed,
+ response_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__, ssif_bmc->smbus_cmd);
+ break;
+ }
+
+ ssif_bmc->nbytes_processed += response_len;
+}
+
+/* Process the IPMI response that will be read by master */
+static void handle_read_processed(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+ u8 *buf;
+ u8 pec_len, addr, len;
+ u8 pec = 0;
+
+ pec_len = ssif_bmc->pec_support ? 1 : 0;
+ /* PEC - Start Read Address */
+ addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
+ pec = i2c_smbus_pec(pec, &addr, 1);
+ /* PEC - SSIF Command */
+ pec = i2c_smbus_pec(pec, &ssif_bmc->smbus_cmd, 1);
+ /* PEC - Restart Write Address */
+ addr = addr | 0x01;
+ pec = i2c_smbus_pec(pec, &addr, 1);
+
+ if (ssif_bmc->is_singlepart_read) {
+ /* Single-part Read processing */
+ buf = (u8 *)&ssif_bmc->response;
+
+ if (ssif_bmc->response.len && ssif_bmc->msg_idx < ssif_bmc->response.len) {
+ ssif_bmc->msg_idx++;
+ *val = buf[ssif_bmc->msg_idx];
+ } else if (ssif_bmc->response.len && ssif_bmc->msg_idx == ssif_bmc->response.len) {
+ ssif_bmc->msg_idx++;
+ *val = i2c_smbus_pec(pec, buf, ssif_msg_len(&ssif_bmc->response));
+ } else {
+ *val = 0;
+ }
+ /* Invalidate response buffer to denote it is sent */
+ if (ssif_bmc->msg_idx + 1 >= (ssif_msg_len(&ssif_bmc->response) + pec_len))
+ complete_response(ssif_bmc);
+ } else {
+ /* Multi-part Read processing */
+ switch (ssif_bmc->smbus_cmd) {
+ case SSIF_IPMI_MULTIPART_READ_START:
+ case SSIF_IPMI_MULTIPART_READ_MIDDLE:
+ buf = (u8 *)&ssif_bmc->response_buf;
+ *val = buf[ssif_bmc->msg_idx];
+ ssif_bmc->msg_idx++;
+ break;
+ default:
+ /* Do not expect to go to this case */
+ dev_err(&ssif_bmc->client->dev,
+ "%s: Unexpected SMBus command 0x%x\n",
+ __func__, ssif_bmc->smbus_cmd);
+ break;
+ }
+
+ len = (ssif_bmc->block_num == 0xFF) ?
+ ssif_bmc->remain_len + 1 : MAX_PAYLOAD_PER_TRANSACTION;
+ if (ssif_bmc->msg_idx == (len + 1)) {
+ pec = i2c_smbus_pec(pec, &len, 1);
+ *val = i2c_smbus_pec(pec, ssif_bmc->response_buf, len);
+ }
+ /* Invalidate response buffer to denote last response is sent */
+ if (ssif_bmc->block_num == 0xFF &&
+ ssif_bmc->msg_idx > (ssif_bmc->remain_len + pec_len)) {
+ complete_response(ssif_bmc);
+ }
+ }
+}
+
+static void handle_write_received(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+ u8 *buf = (u8 *)&ssif_bmc->request;
+
+ if (ssif_bmc->msg_idx >= sizeof(struct ssif_msg))
+ return;
+
+ switch (ssif_bmc->smbus_cmd) {
+ case SSIF_IPMI_SINGLEPART_WRITE:
+ buf[ssif_bmc->msg_idx - 1] = *val;
+ ssif_bmc->msg_idx++;
+
+ break;
+ case SSIF_IPMI_MULTIPART_WRITE_START:
+ if (ssif_bmc->msg_idx == 1)
+ ssif_bmc->request.len = 0;
+
+ fallthrough;
+ case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
+ /* The len should always be 32 */
+ if (ssif_bmc->msg_idx == 1 && *val != MAX_PAYLOAD_PER_TRANSACTION)
+ dev_warn(&ssif_bmc->client->dev,
+ "Warn: Invalid Multipart Write len");
+
+ fallthrough;
+ case SSIF_IPMI_MULTIPART_WRITE_END:
+ /* Multi-part write, 2nd byte received is length */
+ if (ssif_bmc->msg_idx == 1) {
+ if (*val > MAX_PAYLOAD_PER_TRANSACTION)
+ dev_warn(&ssif_bmc->client->dev,
+ "Warn: Invalid Multipart Write End len");
+
+ ssif_bmc->request.len += *val;
+ ssif_bmc->recv_len = *val;
+
+ /* request len should never exceeded 255 bytes */
+ if (ssif_bmc->request.len > 255)
+ dev_warn(&ssif_bmc->client->dev,
+ "Warn: Invalid request len");
+
+ } else {
+ buf[ssif_bmc->msg_idx - 1 +
+ ssif_bmc->request.len - ssif_bmc->recv_len] = *val;
+ }
+
+ ssif_bmc->msg_idx++;
+
+ break;
+ default:
+ /* Do not expect to go to this case */
+ dev_err(&ssif_bmc->client->dev,
+ "%s: Unexpected SMBus command 0x%x\n",
+ __func__, ssif_bmc->smbus_cmd);
+ break;
+ }
+}
+
+static bool validate_request(struct ssif_bmc_ctx *ssif_bmc)
+{
+ u8 rpec = 0, cpec = 0;
+ bool ret = true;
+ u8 addr, index;
+ u8 *buf;
+
+ buf = (u8 *)&ssif_bmc->request;
+ switch (ssif_bmc->smbus_cmd) {
+ case SSIF_IPMI_SINGLEPART_WRITE:
+ if ((ssif_bmc->msg_idx - 1) == ssif_msg_len(&ssif_bmc->request)) {
+ /* PEC is not included */
+ ssif_bmc->pec_support = false;
+ ret = true;
+ goto exit;
+ }
+
+ if ((ssif_bmc->msg_idx - 1) != (ssif_msg_len(&ssif_bmc->request) + 1)) {
+ dev_err(&ssif_bmc->client->dev, "Error: Unexpected length received %d\n",
+ ssif_msg_len(&ssif_bmc->request));
+ ret = false;
+ goto exit;
+ }
+
+ /* PEC is included */
+ ssif_bmc->pec_support = true;
+ rpec = buf[ssif_bmc->msg_idx - 2];
+ addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
+ cpec = i2c_smbus_pec(cpec, &addr, 1);
+ cpec = i2c_smbus_pec(cpec, &ssif_bmc->smbus_cmd, 1);
+ cpec = i2c_smbus_pec(cpec, buf, ssif_msg_len(&ssif_bmc->request));
+ if (rpec != cpec) {
+ dev_err(&ssif_bmc->client->dev, "Bad PEC 0x%02x vs. 0x%02x\n", rpec, cpec);
+ ret = false;
+ }
+
+ break;
+ case SSIF_IPMI_MULTIPART_WRITE_START:
+ case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
+ case SSIF_IPMI_MULTIPART_WRITE_END:
+ index = ssif_bmc->request.len - ssif_bmc->recv_len;
+ if ((ssif_bmc->msg_idx - 1 + index) == ssif_msg_len(&ssif_bmc->request)) {
+ /* PEC is not included */
+ ssif_bmc->pec_support = false;
+ ret = true;
+ goto exit;
+ }
+
+ if ((ssif_bmc->msg_idx - 1 + index) != (ssif_msg_len(&ssif_bmc->request) + 1)) {
+ dev_err(&ssif_bmc->client->dev, "Error: Unexpected length received %d\n",
+ ssif_msg_len(&ssif_bmc->request));
+ ret = false;
+ goto exit;
+ }
+
+ /* PEC is included */
+ ssif_bmc->pec_support = true;
+ rpec = buf[ssif_bmc->msg_idx - 2 + index];
+ addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
+ cpec = i2c_smbus_pec(cpec, &addr, 1);
+ cpec = i2c_smbus_pec(cpec, &ssif_bmc->smbus_cmd, 1);
+ cpec = i2c_smbus_pec(cpec, &ssif_bmc->recv_len, 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 (ssif_bmc->recv_len != 0)
+ cpec = i2c_smbus_pec(cpec, buf + 1 + index, ssif_bmc->recv_len);
+
+ if (rpec != cpec) {
+ dev_err(&ssif_bmc->client->dev, "Bad PEC 0x%02x vs. 0x%02x\n", rpec, cpec);
+ ret = false;
+ }
+
+ break;
+ default:
+ /* Do not expect to go to this case */
+ dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus command 0x%x\n",
+ __func__, ssif_bmc->smbus_cmd);
+ ret = false;
+ break;
+ }
+
+exit:
+ return ret;
+}
+
+static bool unsupported_smbus_cmd(u8 cmd)
+{
+ if (cmd == SSIF_IPMI_SINGLEPART_READ ||
+ cmd == SSIF_IPMI_SINGLEPART_WRITE ||
+ cmd == SSIF_IPMI_MULTIPART_WRITE_START ||
+ cmd == SSIF_IPMI_MULTIPART_WRITE_MIDDLE ||
+ cmd == SSIF_IPMI_MULTIPART_WRITE_END ||
+ cmd == SSIF_IPMI_MULTIPART_READ_START ||
+ cmd == SSIF_IPMI_MULTIPART_READ_MIDDLE)
+ return false;
+
+ return true;
+}
+
+static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+ /* SMBUS command can vary (single or multi-part) */
+ ssif_bmc->smbus_cmd = *val;
+ ssif_bmc->msg_idx++;
+
+ if (unsupported_smbus_cmd(*val))
+ dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus command");
+
+ 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);
+ }
+}
+
+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) {
+ ssif_bmc->state = SSIF_BAD_SMBUS;
+ dev_warn(&ssif_bmc->client->dev,
+ "Warn: %s unexpected READ REQUESTED in state=%s\n",
+ __func__, state_to_string(ssif_bmc->state));
+
+ } else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
+ ssif_bmc->state = SSIF_RES_SENDING;
+ }
+
+ ssif_bmc->msg_idx = 0;
+ if (ssif_bmc->is_singlepart_read)
+ *val = ssif_bmc->response.len;
+ else
+ set_multipart_response_buffer(ssif_bmc, val);
+}
+
+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_BAD_SMBUS;
+ }
+
+ handle_read_processed(ssif_bmc, val);
+}
+
+static void on_write_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
+{
+ ssif_bmc->msg_idx = 0;
+
+ 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_BAD_SMBUS;
+ }
+}
+
+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_BAD_SMBUS;
+ } else if (ssif_bmc->state == SSIF_START) {
+ ssif_bmc->state = SSIF_SMBUS_CMD;
+ } else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
+ 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) {
+ dev_warn(&ssif_bmc->client->dev,
+ "Warn: %s unexpected SLAVE STOP in state=%s\n",
+ __func__, state_to_string(ssif_bmc->state));
+
+ } else if (ssif_bmc->state == SSIF_BAD_SMBUS) {
+ dev_warn(&ssif_bmc->client->dev,
+ "Warn: %s received SLAVE STOP from bad state=%s\n",
+ __func__, state_to_string(ssif_bmc->state));
+
+ } else if (ssif_bmc->state == SSIF_REQ_RECVING) {
+ /* 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
+ */
+ if (!validate_request(ssif_bmc))
+ dev_err(&ssif_bmc->client->dev, "Error: invalid pec\n");
+ else if (ssif_bmc->smbus_cmd == SSIF_IPMI_SINGLEPART_WRITE ||
+ ssif_bmc->smbus_cmd == SSIF_IPMI_MULTIPART_WRITE_END)
+ handle_request(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->busy)
+ ret = -EBUSY;
+
+ spin_unlock_irqrestore(&ssif_bmc->lock, flags);
+
+ return ret;
+}
+
+static int ssif_bmc_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+ 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)
+ goto out;
+
+ 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);
+ goto out;
+ }
+
+ return 0;
+out:
+ devm_kfree(&client->dev, ssif_bmc);
+ return ret;
+}
+
+static int 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);
+
+ return 0;
+}
+
+static const struct of_device_id ssif_bmc_match[] = {
+ { .compatible = "ampere,ssif-bmc" },
+ { },
+};
+
+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 = 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");
diff --git a/drivers/char/ipmi/ssif_bmc.h b/drivers/char/ipmi/ssif_bmc.h
new file mode 100644
index 000000000000..9a26f3c252cc
--- /dev/null
+++ b/drivers/char/ipmi/ssif_bmc.h
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * The driver for BMC side of SSIF interface
+ *
+ * Copyright (c) 2022, Ampere Computing LLC
+ *
+ */
+#ifndef __SSIF_BMC_H__
+#define __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
+
+#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
+
+#define MSG_PAYLOAD_LEN_MAX 252
+/*
+ * 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 upto 500ms
+ */
+#define RESPONSE_TIMEOUT 500 /* ms */
+
+struct ssif_msg {
+ u8 len;
+ u8 netfn_lun;
+ u8 cmd;
+ u8 payload[MSG_PAYLOAD_LEN_MAX];
+} __packed;
+
+static inline u32 ssif_msg_len(struct ssif_msg *ssif_msg)
+{
+ return ssif_msg->len + 1;
+}
+
+/*
+ * 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_BAD_SMBUS 0x05 : Bad SMbus transaction
+ */
+enum ssif_state {
+ SSIF_READY,
+ SSIF_START,
+ SSIF_SMBUS_CMD,
+ SSIF_REQ_RECVING,
+ SSIF_RES_SENDING,
+ SSIF_BAD_SMBUS,
+ SSIF_STATE_MAX
+};
+
+struct ssif_bmc_ctx {
+ struct i2c_client *client;
+ struct miscdevice miscdev;
+ size_t msg_idx;
+ bool pec_support;
+ /* ssif bmc spinlock */
+ spinlock_t lock;
+ wait_queue_head_t wait_queue;
+ u8 running;
+ enum ssif_state state;
+ u8 smbus_cmd;
+ /* 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;
+ /* Response buffer for Multi-part Read Transaction */
+ u8 response_buf[MAX_PAYLOAD_PER_TRANSACTION];
+ struct ssif_msg response;
+ struct 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);
+}
+#endif /* __SSIF_BMC_H__ */
--
2.35.1