Support IPMB in OpenBMC
Haiyue Wang
haiyue.wang at linux.intel.com
Wed Mar 14 16:15:43 AEDT 2018
According to the document of https://goo.gl/WgvPFi
IPMI is embedded within IPMB
...
- We need a kernel interface for handling a multi-master slave
- Brendan suggests we need a kernel driver for doing both MCTP and IPMB
- Slave mode is not yet exposed to the user
- As we don’t have a userspace interface, it makes sense to add a new one
We developed a driver based on linux dev-4.10 branch tree, called it as mqueue
(message queue) I2C slave backend.
Just for sharing.
If people have more ideas, welcome to discussing. :-)
BR,
Haiyue
---
Documentation/i2c/slave-mqueue-backend.rst | 125 ++++++++++++++++++
drivers/i2c/Kconfig | 13 ++
drivers/i2c/Makefile | 1 +
drivers/i2c/i2c-slave-mqueue.c | 202 +++++++++++++++++++++++++++++
4 files changed, 341 insertions(+)
create mode 100644 Documentation/i2c/slave-mqueue-backend.rst
create mode 100644 drivers/i2c/i2c-slave-mqueue.c
diff --git a/Documentation/i2c/slave-mqueue-backend.rst b/Documentation/i2c/slave-mqueue-backend.rst
new file mode 100644
index 0000000..69d6437
--- /dev/null
+++ b/Documentation/i2c/slave-mqueue-backend.rst
@@ -0,0 +1,125 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+Linux I2C slave message queue backend
+=====================================
+
+:Author: Haiyue Wang <haiyue.wang at linux.intel.com>
+
+Some protocols over I2C/SMBus are designed for bi-directional transferring
+messages by using I2C Master Write protocol. This requires that both sides
+of the communication have slave addresses.
+
+Like MCTP (Management Component Transport Protocol) and IPMB (Intelligent
+Platform Management Bus), they both require that the userspace can receive
+messages from i2c dirvers under slave mode.
+
+This I2C slave mqueue (message queue) backend is used to receive and queue
+messages from the remote i2c intelligent device; and it will add the target
+slave address (with R/W# bit is always 0) into the message at the first byte,
+so that userspace can use this byte to dispatch the messages into different
+handling modules. Also, like IPMB, the address byte is in its message format,
+it needs it to do checksum.
+
+For messages are time related, so this backend will flush the oldest message
+to queue the newest one.
+
+Link
+----
+`Intelligent Platform Management Bus
+Communications Protocol Specification
+<https://www.intel.com/content/dam/www/public/us/en/documents/product-briefs/ipmp-spec-v1.0.pdf>`_
+
+`Management Component Transport Protocol (MCTP)
+SMBus/I2C Transport Binding Specification
+<https://www.dmtf.org/sites/default/files/standards/documents/DSP0237_1.1.0.pdf>`_
+
+How to use
+----------
+For example, the I2C5 bus has slave address 0x10, bellowing command will create
+the related message queue interface:
+
+ echo slave-mqueue 0x1010 > /sys/bus/i2c/devices/i2c-5/new_device
+
+Then you can dump the messages like this:
+
+ hexdump -C /sys/bus/i2c/devices/5-1010/slave-mqueue
+
+Code Example
+------------
+*Note: call 'lseek' before 'read', this is a requirement from kernfs' design.*
+
+::
+
+ #include <sys/types.h>
+ #include <sys/stat.h>
+ #include <unistd.h>
+ #include <poll.h>
+ #include <time.h>
+ #include <fcntl.h>
+ #include <stdio.h>
+
+ int main(int argc, char *argv[])
+ {
+ int i, r;
+ struct pollfd pfd;
+ struct timespec ts;
+ unsigned char data[256];
+
+ pfd.fd = open(argv[1], O_RDONLY | O_NONBLOCK);
+ if (pfd.fd < 0)
+ return -1;
+
+ pfd.events = POLLPRI;
+
+ while (1) {
+ r = poll(&pfd, 1, 5000);
+
+ if (r < 0)
+ break;
+
+ if (r == 0 || !(pfd.revents & POLLPRI))
+ continue;
+
+ lseek(pfd.fd, 0, SEEK_SET);
+ r = read(pfd.fd, data, sizeof(data));
+ if (r <= 0)
+ continue;
+
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+ printf("[%ld.%.9ld] :", ts.tv_sec, ts.tv_nsec);
+ for (i = 0; i < r; i++)
+ printf(" %02x", data[i]);
+ printf("\n");
+ }
+
+ close(pfd.fd);
+
+ return 0;
+ }
+
+Result
+------
+*./a.out "/sys/bus/i2c/devices/5-1010/slave-mqueue"*
+
+::
+
+ [10183.232500449] : 20 18 c8 2c 78 01 5b
+ [10183.479358348] : 20 18 c8 2c 78 01 5b
+ [10183.726556812] : 20 18 c8 2c 78 01 5b
+ [10183.972605863] : 20 18 c8 2c 78 01 5b
+ [10184.220124772] : 20 18 c8 2c 78 01 5b
+ [10184.467764166] : 20 18 c8 2c 78 01 5b
+ [10193.233421784] : 20 18 c8 2c 7c 01 57
+ [10193.480273460] : 20 18 c8 2c 7c 01 57
+ [10193.726788733] : 20 18 c8 2c 7c 01 57
+ [10193.972781945] : 20 18 c8 2c 7c 01 57
+ [10194.220487360] : 20 18 c8 2c 7c 01 57
+ [10194.468089259] : 20 18 c8 2c 7c 01 57
+ [10203.233433099] : 20 18 c8 2c 80 01 53
+ [10203.481058715] : 20 18 c8 2c 80 01 53
+ [10203.727610472] : 20 18 c8 2c 80 01 53
+ [10203.974044856] : 20 18 c8 2c 80 01 53
+ [10204.220734634] : 20 18 c8 2c 80 01 53
+ [10204.468461664] : 20 18 c8 2c 80 01 53
+
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index efc3354..7053b5b 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -118,6 +118,19 @@ if I2C_SLAVE
config I2C_SLAVE_EEPROM
tristate "I2C eeprom slave driver"
+config I2C_SLAVE_MQUEUE
+ tristate "I2C mqueue (message queue) slave driver"
+ help
+ Some protocols over I2C are designed for bi-directional transferring
+ messages by using I2C Master Write protocol. This driver is used to
+ receive and queue messages from the remote I2C device.
+
+ Userspace can get the messages by reading sysfs file that this driver
+ exposes.
+
+ This support is also available as a module. If so, the module will be
+ called i2c-slave-mqueue.
+
endif
config I2C_DEBUG_CORE
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index 45095b3..e94442f 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_I2C_MUX) += i2c-mux.o
obj-y += algos/ busses/ muxes/
obj-$(CONFIG_I2C_STUB) += i2c-stub.o
obj-$(CONFIG_I2C_SLAVE_EEPROM) += i2c-slave-eeprom.o
+obj-$(CONFIG_I2C_SLAVE_MQUEUE) += i2c-slave-mqueue.o
ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
CFLAGS_i2c-core.o := -Wno-deprecated-declarations
diff --git a/drivers/i2c/i2c-slave-mqueue.c b/drivers/i2c/i2c-slave-mqueue.c
new file mode 100644
index 0000000..a486e85
--- /dev/null
+++ b/drivers/i2c/i2c-slave-mqueue.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 - 2018, Intel Corporation.
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+
+#define MQ_MSGBUF_SIZE 128
+#define MQ_QUEUE_SIZE 32
+#define MQ_QUEUE_NEXT(x) (((x) + 1) & (MQ_QUEUE_SIZE - 1))
+
+struct mq_msg {
+ int len;
+ u8 *buf;
+};
+
+struct mq_queue {
+ struct bin_attribute bin;
+ struct kernfs_node *kn;
+
+ spinlock_t lock; /* spinlock for queue index handling */
+ int in;
+ int out;
+
+ struct mq_msg *curr;
+ int truncated; /* drop current if truncated */
+ struct mq_msg queue[MQ_QUEUE_SIZE];
+};
+
+static int i2c_slave_mqueue_callback(struct i2c_client *client,
+ enum i2c_slave_event event, u8 *val)
+{
+ struct mq_queue *mq = i2c_get_clientdata(client);
+ struct mq_msg *msg = mq->curr;
+ int ret = 0;
+
+ switch (event) {
+ case I2C_SLAVE_WRITE_REQUESTED:
+ mq->truncated = 0;
+
+ msg->len = 1;
+ msg->buf[0] = client->addr << 1;
+ break;
+
+ case I2C_SLAVE_WRITE_RECEIVED:
+ if (msg->len < MQ_MSGBUF_SIZE) {
+ msg->buf[msg->len++] = *val;
+ } else {
+ dev_err(&client->dev, "message is truncated!\n");
+ mq->truncated = 1;
+ ret = -EINVAL;
+ }
+ break;
+
+ case I2C_SLAVE_STOP:
+ if (unlikely(mq->truncated))
+ break;
+
+ spin_lock(&mq->lock);
+ mq->in = MQ_QUEUE_NEXT(mq->in);
+ mq->curr = &mq->queue[mq->in];
+
+ /* Flush the oldest message */
+ if (mq->out == mq->in)
+ mq->out = MQ_QUEUE_NEXT(mq->out);
+ spin_unlock(&mq->lock);
+
+ kernfs_notify(mq->kn);
+ break;
+
+ default:
+ *val = 0xFF;
+ break;
+ }
+
+ return ret;
+}
+
+static ssize_t i2c_slave_mqueue_bin_read(struct file *filp,
+ struct kobject *kobj,
+ struct bin_attribute *attr,
+ char *buf, loff_t pos, size_t count)
+{
+ struct mq_queue *mq;
+ struct mq_msg *msg;
+ unsigned long flags;
+ bool more = false;
+ ssize_t ret = 0;
+
+ mq = dev_get_drvdata(container_of(kobj, struct device, kobj));
+
+ spin_lock_irqsave(&mq->lock, flags);
+ if (mq->out != mq->in) {
+ msg = &mq->queue[mq->out];
+
+ if (msg->len <= count) {
+ ret = msg->len;
+ memcpy(buf, msg->buf, ret);
+ } else {
+ ret = -EOVERFLOW; /* Drop this HUGE one. */
+ }
+
+ mq->out = MQ_QUEUE_NEXT(mq->out);
+ if (mq->out != mq->in)
+ more = true;
+ }
+ spin_unlock_irqrestore(&mq->lock, flags);
+
+ if (more)
+ kernfs_notify(mq->kn);
+
+ return ret;
+}
+
+static int i2c_slave_mqueue_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct device *dev = &client->dev;
+ struct mq_queue *mq;
+ int ret, i;
+ void *buf;
+
+ mq = devm_kzalloc(dev, sizeof(*mq), GFP_KERNEL);
+ if (!mq)
+ return -ENOMEM;
+
+ BUILD_BUG_ON(!is_power_of_2(MQ_QUEUE_SIZE));
+
+ buf = devm_kmalloc_array(dev, MQ_QUEUE_SIZE, MQ_MSGBUF_SIZE,
+ GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ for (i = 0; i < MQ_QUEUE_SIZE; i++)
+ mq->queue[i].buf = buf + i * MQ_MSGBUF_SIZE;
+
+ i2c_set_clientdata(client, mq);
+
+ spin_lock_init(&mq->lock);
+ mq->curr = &mq->queue[0];
+
+ sysfs_bin_attr_init(&mq->bin);
+ mq->bin.attr.name = "slave-mqueue";
+ mq->bin.attr.mode = 0400;
+ mq->bin.read = i2c_slave_mqueue_bin_read;
+ mq->bin.size = MQ_MSGBUF_SIZE * MQ_QUEUE_SIZE;
+
+ ret = sysfs_create_bin_file(&dev->kobj, &mq->bin);
+ if (ret)
+ return ret;
+
+ mq->kn = kernfs_find_and_get(dev->kobj.sd, mq->bin.attr.name);
+ if (!mq->kn) {
+ sysfs_remove_bin_file(&dev->kobj, &mq->bin);
+ return -EFAULT;
+ }
+
+ ret = i2c_slave_register(client, i2c_slave_mqueue_callback);
+ if (ret) {
+ kernfs_put(mq->kn);
+ sysfs_remove_bin_file(&dev->kobj, &mq->bin);
+ return ret;
+ }
+
+ return 0;
+};
+
+static int i2c_slave_mqueue_remove(struct i2c_client *client)
+{
+ struct mq_queue *mq = i2c_get_clientdata(client);
+
+ i2c_slave_unregister(client);
+
+ kernfs_put(mq->kn);
+ sysfs_remove_bin_file(&client->dev.kobj, &mq->bin);
+
+ return 0;
+}
+
+static const struct i2c_device_id i2c_slave_mqueue_id[] = {
+ { "slave-mqueue", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, i2c_slave_mqueue_id);
+
+static struct i2c_driver i2c_slave_mqueue_driver = {
+ .driver = {
+ .name = "i2c-slave-mqueue",
+ },
+ .probe = i2c_slave_mqueue_probe,
+ .remove = i2c_slave_mqueue_remove,
+ .id_table = i2c_slave_mqueue_id,
+};
+module_i2c_driver(i2c_slave_mqueue_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Haiyue Wang <haiyue.wang at linux.intel.com>");
+MODULE_DESCRIPTION("I2C slave mode for receiving and queuing messages");
--
2.7.4
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