Date:   Fri,  4 Aug 2017 18:18:53 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     corbet@....net, robh+dt@...nel.org, mark.rutland@....com,
        arnd@...db.de, gregkh@...uxfoundation.org, minyard@....org,
        joel@....id.au, benh@...nel.crashing.org, benjaminfair@...gle.com
Cc:     linux-doc@...r.kernel.org, devicetree@...r.kernel.org,
        openipmi-developer@...ts.sourceforge.net, openbmc@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Brendan Higgins <brendanhiggins@...gle.com>
Subject: [PATCH v2 2/4] ipmi: bt-i2c: added IPMI Block Transfer over I2C host side

The IPMI definition of the Block Transfer protocol defines the hardware
registers and behavior in addition to the message format and messaging
semantics. This implements a new protocol that uses IPMI Block Transfer
messages and semantics on top of a standard I2C interface.

Signed-off-by: Brendan Higgins <brendanhiggins@...gle.com>
---
Changes for v2:
  - None
---
 drivers/char/ipmi/Kconfig       |   4 +
 drivers/char/ipmi/Makefile      |   1 +
 drivers/char/ipmi/ipmi_bt_i2c.c | 452 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 457 insertions(+)
 create mode 100644 drivers/char/ipmi/ipmi_bt_i2c.c

diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
index f6fa056a52fc..a8734a369cb0 100644
--- a/drivers/char/ipmi/Kconfig
+++ b/drivers/char/ipmi/Kconfig
@@ -79,6 +79,10 @@ config IPMI_POWEROFF
          This enables a function to power off the system with IPMI if
 	 the IPMI management controller is capable of this.
 
+config IPMI_BT_I2C
+	select I2C
+	tristate 'BT IPMI bmc driver over I2c'
+
 endif # IPMI_HANDLER
 
 config ASPEED_BT_IPMI_BMC
diff --git a/drivers/char/ipmi/Makefile b/drivers/char/ipmi/Makefile
index eefb0b301e83..323de0b0b8b5 100644
--- a/drivers/char/ipmi/Makefile
+++ b/drivers/char/ipmi/Makefile
@@ -12,4 +12,5 @@ obj-$(CONFIG_IPMI_SSIF) += ipmi_ssif.o
 obj-$(CONFIG_IPMI_POWERNV) += ipmi_powernv.o
 obj-$(CONFIG_IPMI_WATCHDOG) += ipmi_watchdog.o
 obj-$(CONFIG_IPMI_POWEROFF) += ipmi_poweroff.o
+obj-$(CONFIG_IPMI_BT_I2C) += ipmi_bt_i2c.o
 obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
diff --git a/drivers/char/ipmi/ipmi_bt_i2c.c b/drivers/char/ipmi/ipmi_bt_i2c.c
new file mode 100644
index 000000000000..94b5c11d23cd
--- /dev/null
+++ b/drivers/char/ipmi/ipmi_bt_i2c.c
@@ -0,0 +1,452 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * 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.
+ */
+
+#define pr_fmt(fmt)        "ipmi-bt-i2c: " fmt
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/ipmi_smi.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/timer.h>
+#include <linux/jiffies.h>
+#include <linux/types.h>
+
+#define IPMI_BT_I2C_TIMEOUT (msecs_to_jiffies(1000))
+
+/* If we don't have netfn_lun, seq, and cmd, we might as well have nothing. */
+#define IPMI_BT_I2C_LEN_MIN 3
+/* We need at least netfn_lun, seq, cmd, and completion. */
+#define IPMI_BT_I2C_RESPONSE_LEN_MIN 4
+#define IPMI_BT_I2C_MSG_MAX_PAYLOAD_SIZE 252
+
+struct ipmi_bt_i2c_msg {
+	u8 len;
+	u8 netfn_lun;
+	u8 seq;
+	u8 cmd;
+	u8 payload[IPMI_BT_I2C_MSG_MAX_PAYLOAD_SIZE];
+} __packed;
+
+#define IPMI_BT_I2C_MAX_SMI_SIZE 254 /* Need extra byte for seq. */
+#define IPMI_BT_I2C_SMI_MSG_HEADER_SIZE 2
+
+struct ipmi_bt_i2c_smi_msg {
+	u8 netfn_lun;
+	u8 cmd;
+	u8 payload[IPMI_MAX_MSG_LENGTH - 2];
+} __packed;
+
+static inline u32 bt_msg_len(struct ipmi_bt_i2c_msg *bt_request)
+{
+	return bt_request->len + 1;
+}
+
+#define IPMI_BT_I2C_SEQ_MAX 256
+
+struct ipmi_bt_i2c_seq_entry {
+	struct ipmi_smi_msg		*msg;
+	unsigned long			send_time;
+};
+
+struct ipmi_bt_i2c_master {
+	struct ipmi_device_id		ipmi_id;
+	struct i2c_client		*client;
+	ipmi_smi_t			intf;
+	spinlock_t			lock;
+	struct ipmi_bt_i2c_seq_entry	seq_msg_map[IPMI_BT_I2C_SEQ_MAX];
+	struct work_struct		ipmi_bt_i2c_recv_work;
+	struct work_struct		ipmi_bt_i2c_send_work;
+	struct ipmi_smi_msg		*msg_to_send;
+};
+
+static const unsigned long write_timeout = 25;
+
+static int ipmi_bt_i2c_send_request(struct ipmi_bt_i2c_master *master,
+				    struct ipmi_bt_i2c_msg *request)
+{
+	struct i2c_client *client = master->client;
+	unsigned long timeout, read_time;
+	u8 *buf = (u8 *) request;
+	int ret;
+
+	timeout = jiffies + msecs_to_jiffies(write_timeout);
+	do {
+		read_time = jiffies;
+		ret = i2c_master_send(client, buf, bt_msg_len(request));
+		if (ret >= 0)
+			return 0;
+		usleep_range(1000, 1500);
+	} while (time_before(read_time, timeout));
+	return ret;
+}
+
+static int ipmi_bt_i2c_receive_response(struct ipmi_bt_i2c_master *master,
+					struct ipmi_bt_i2c_msg *response)
+{
+	struct i2c_client *client = master->client;
+	unsigned long timeout, read_time;
+	u8 *buf = (u8 *) response;
+	u8 len = 0;
+	int ret;
+
+	/*
+	 * Slave may not NACK when not ready, so we peek at the first byte to
+	 * see if it is a valid length.
+	 */
+	ret = i2c_master_recv(client, &len, 1);
+	while (ret != 1 || len == 0) {
+		if (ret < 0)
+			return ret;
+
+		usleep_range(1000, 1500);
+
+		/* Signal received: quit syscall. */
+		if (signal_pending(current))
+			return -ERESTARTSYS;
+
+		ret = i2c_master_recv(client, &len, 1);
+	}
+
+	timeout = jiffies + msecs_to_jiffies(write_timeout);
+	do {
+		read_time = jiffies;
+		ret = i2c_master_recv(client, buf, len + 1);
+		if (ret >= 0)
+			return 0;
+		usleep_range(1000, 1500);
+	} while (time_before(read_time, timeout));
+	return ret;
+}
+
+static int ipmi_bt_i2c_start_processing(void *data, ipmi_smi_t intf)
+{
+	struct ipmi_bt_i2c_master *master = data;
+
+	master->intf = intf;
+
+	return 0;
+}
+
+static void __ipmi_bt_i2c_error_reply(struct ipmi_bt_i2c_master *master,
+				      struct ipmi_smi_msg *msg,
+				      u8 completion_code)
+{
+	struct ipmi_bt_i2c_smi_msg *response;
+	struct ipmi_bt_i2c_smi_msg *request;
+
+	response = (struct ipmi_bt_i2c_smi_msg *) msg->rsp;
+	request = (struct ipmi_bt_i2c_smi_msg *) msg->data;
+
+	response->netfn_lun = request->netfn_lun | 0x4;
+	response->cmd = request->cmd;
+	response->payload[0] = completion_code;
+	msg->rsp_size = 3;
+	ipmi_smi_msg_received(master->intf, msg);
+}
+
+static void ipmi_bt_i2c_error_reply(struct ipmi_bt_i2c_master *master,
+				    struct ipmi_smi_msg *msg,
+				    u8 completion_code)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&master->lock, flags);
+	__ipmi_bt_i2c_error_reply(master, msg, completion_code);
+	spin_unlock_irqrestore(&master->lock, flags);
+}
+
+/*
+ * ipmi_bt_i2c_smi_msg contains a payload and 2 header fields, each 1 byte:
+ * netfn_lun and cmd. They're passed to OpenIPMI within an ipmi_smi_msg struct
+ * along with their length.
+ *
+ * ipmi_bt_i2c_msg contains a payload and 4 header fields: the two above in
+ * addition to seq and len. However, len is not included in the length count so
+ * this message encapsulation is considered 1 byte longer than the other.
+ */
+static u8 ipmi_bt_i2c_smi_to_bt_len(u8 smi_msg_len)
+{
+	/* Only field that BT adds to the header is seq. */
+	return smi_msg_len + 1;
+}
+
+static u8 ipmi_bt_i2c_bt_to_smi_len(struct ipmi_bt_i2c_msg *bt_msg)
+{
+	/* Subtract one byte for seq (opposite of above) */
+	return bt_msg->len - 1;
+}
+
+static size_t ipmi_bt_i2c_payload_len(struct ipmi_bt_i2c_msg *bt_msg)
+{
+	/* Subtract one byte for each: netfn_lun, seq, cmd. */
+	return bt_msg->len - 3;
+}
+
+static bool ipmi_bt_i2c_assign_seq(struct ipmi_bt_i2c_master *master,
+				   struct ipmi_smi_msg *msg, u8 *ret_seq)
+{
+	struct ipmi_bt_i2c_seq_entry *entry;
+	bool did_cleanup = false;
+	unsigned long flags;
+	u8 seq;
+
+	spin_lock_irqsave(&master->lock, flags);
+retry:
+	for (seq = 0; seq < IPMI_BT_I2C_SEQ_MAX; seq++) {
+		if (!master->seq_msg_map[seq].msg) {
+			master->seq_msg_map[seq].msg = msg;
+			master->seq_msg_map[seq].send_time = jiffies;
+			spin_unlock_irqrestore(&master->lock, flags);
+			*ret_seq = seq;
+			return true;
+		}
+	}
+
+	if (did_cleanup) {
+		spin_unlock_irqrestore(&master->lock, flags);
+		return false;
+	}
+
+	/*
+	 * TODO: we should do cleanup at times other than only when we run out
+	 * of sequence numbers.
+	 */
+	for (seq = 0; seq < IPMI_BT_I2C_SEQ_MAX; seq++) {
+		entry = &master->seq_msg_map[seq];
+		if (entry->msg &&
+		    time_after(entry->send_time + IPMI_BT_I2C_TIMEOUT,
+			       jiffies)) {
+			__ipmi_bt_i2c_error_reply(master, entry->msg,
+						  IPMI_TIMEOUT_ERR);
+			entry->msg = NULL;
+		}
+	}
+	did_cleanup = true;
+	goto retry;
+}
+
+static struct ipmi_smi_msg *ipmi_bt_i2c_find_msg(
+		struct ipmi_bt_i2c_master *master, u8 seq)
+{
+	struct ipmi_smi_msg *msg;
+	unsigned long flags;
+
+	spin_lock_irqsave(&master->lock, flags);
+	msg = master->seq_msg_map[seq].msg;
+	spin_unlock_irqrestore(&master->lock, flags);
+	return msg;
+}
+
+static void ipmi_bt_i2c_free_seq(struct ipmi_bt_i2c_master *master, u8 seq)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&master->lock, flags);
+	master->seq_msg_map[seq].msg = NULL;
+	spin_unlock_irqrestore(&master->lock, flags);
+}
+
+static void ipmi_bt_i2c_send_workfn(struct work_struct *work)
+{
+	struct ipmi_bt_i2c_smi_msg *smi_msg;
+	struct ipmi_bt_i2c_master *master;
+	struct ipmi_bt_i2c_msg bt_msg;
+	struct ipmi_smi_msg *msg;
+	size_t smi_msg_size;
+	unsigned long flags;
+
+	master = container_of(work, struct ipmi_bt_i2c_master,
+			      ipmi_bt_i2c_send_work);
+
+	msg = master->msg_to_send;
+	smi_msg_size = msg->data_size;
+	smi_msg = (struct ipmi_bt_i2c_smi_msg *) msg->data;
+
+	if (smi_msg_size > IPMI_BT_I2C_MAX_SMI_SIZE) {
+		ipmi_bt_i2c_error_reply(master, msg, IPMI_REQ_LEN_EXCEEDED_ERR);
+		return;
+	}
+
+	if (smi_msg_size < IPMI_BT_I2C_SMI_MSG_HEADER_SIZE) {
+		ipmi_bt_i2c_error_reply(master, msg, IPMI_REQ_LEN_INVALID_ERR);
+		return;
+	}
+
+	if (!ipmi_bt_i2c_assign_seq(master, msg, &bt_msg.seq)) {
+		ipmi_bt_i2c_error_reply(master, msg, IPMI_NODE_BUSY_ERR);
+		return;
+	}
+
+	bt_msg.len = ipmi_bt_i2c_smi_to_bt_len(smi_msg_size);
+	bt_msg.netfn_lun = smi_msg->netfn_lun;
+	bt_msg.cmd = smi_msg->cmd;
+	memcpy(bt_msg.payload, smi_msg->payload,
+	       ipmi_bt_i2c_payload_len(&bt_msg));
+
+	if (ipmi_bt_i2c_send_request(master, &bt_msg) < 0) {
+		ipmi_bt_i2c_free_seq(master, bt_msg.seq);
+		ipmi_bt_i2c_error_reply(master, msg, IPMI_BUS_ERR);
+	}
+
+	spin_lock_irqsave(&master->lock, flags);
+	master->msg_to_send = NULL;
+	spin_unlock_irqrestore(&master->lock, flags);
+}
+
+void ipmi_bt_i2c_recv_workfn(struct work_struct *work)
+{
+	struct ipmi_bt_i2c_smi_msg *smi_msg;
+	struct ipmi_bt_i2c_master *master;
+	struct ipmi_bt_i2c_msg bt_msg;
+	struct ipmi_smi_msg *msg;
+
+	master = container_of(work, struct ipmi_bt_i2c_master,
+			      ipmi_bt_i2c_recv_work);
+
+	if (ipmi_bt_i2c_receive_response(master, &bt_msg) < 0)
+		return;
+
+	if (bt_msg.len < IPMI_BT_I2C_LEN_MIN)
+		return;
+
+	msg = ipmi_bt_i2c_find_msg(master, bt_msg.seq);
+	if (!msg)
+		return;
+
+	ipmi_bt_i2c_free_seq(master, bt_msg.seq);
+
+	if (bt_msg.len < IPMI_BT_I2C_RESPONSE_LEN_MIN)
+		ipmi_bt_i2c_error_reply(master, msg, IPMI_ERR_MSG_TRUNCATED);
+
+	msg->rsp_size = ipmi_bt_i2c_bt_to_smi_len(&bt_msg);
+	smi_msg = (struct ipmi_bt_i2c_smi_msg *) msg->rsp;
+	smi_msg->netfn_lun = bt_msg.netfn_lun;
+	smi_msg->cmd = bt_msg.cmd;
+	memcpy(smi_msg->payload, bt_msg.payload,
+	       ipmi_bt_i2c_payload_len(&bt_msg));
+	ipmi_smi_msg_received(master->intf, msg);
+}
+
+static void ipmi_bt_i2c_sender(void *data, struct ipmi_smi_msg *msg)
+{
+	struct ipmi_bt_i2c_master *master = data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&master->lock, flags);
+	if (master->msg_to_send) {
+		/*
+		 * TODO(benjaminfair): Queue messages to send instead of only
+		 * keeping one.
+		 */
+		__ipmi_bt_i2c_error_reply(master, msg, IPMI_NODE_BUSY_ERR);
+	} else {
+		master->msg_to_send = msg;
+		schedule_work(&master->ipmi_bt_i2c_send_work);
+	}
+	spin_unlock_irqrestore(&master->lock, flags);
+}
+
+static void ipmi_bt_i2c_request_events(void *data)
+{
+	struct ipmi_bt_i2c_master *master = data;
+
+	schedule_work(&master->ipmi_bt_i2c_recv_work);
+}
+
+static void ipmi_bt_i2c_set_run_to_completion(void *data,
+					      bool run_to_completion)
+{
+}
+
+static void ipmi_bt_i2c_poll(void *data)
+{
+	struct ipmi_bt_i2c_master *master = data;
+
+	schedule_work(&master->ipmi_bt_i2c_recv_work);
+}
+
+static struct ipmi_smi_handlers ipmi_bt_i2c_smi_handlers = {
+	.owner			= THIS_MODULE,
+	.start_processing	= ipmi_bt_i2c_start_processing,
+	.sender			= ipmi_bt_i2c_sender,
+	.request_events		= ipmi_bt_i2c_request_events,
+	.set_run_to_completion	= ipmi_bt_i2c_set_run_to_completion,
+	.poll			= ipmi_bt_i2c_poll,
+};
+
+static int ipmi_bt_i2c_probe(struct i2c_client *client,
+			     const struct i2c_device_id *id)
+{
+	struct ipmi_bt_i2c_master *master;
+	int ret;
+
+	master = devm_kzalloc(&client->dev, sizeof(struct ipmi_bt_i2c_master),
+			      GFP_KERNEL);
+	if (!master)
+		return -ENOMEM;
+
+	spin_lock_init(&master->lock);
+	INIT_WORK(&master->ipmi_bt_i2c_recv_work, ipmi_bt_i2c_recv_workfn);
+	INIT_WORK(&master->ipmi_bt_i2c_send_work, ipmi_bt_i2c_send_workfn);
+	master->client = client;
+	i2c_set_clientdata(client, master);
+
+	/*
+	 * TODO(benjaminfair): read ipmi_device_id from BMC to determine version
+	 * information and be able to tell multiple BMCs apart
+	 */
+	ret = ipmi_register_smi(&ipmi_bt_i2c_smi_handlers, master,
+				&master->ipmi_id, &client->dev, 0);
+
+	return ret;
+}
+
+static int ipmi_bt_i2c_remove(struct i2c_client *client)
+{
+	struct ipmi_bt_i2c_master *master;
+
+	master = i2c_get_clientdata(client);
+	return ipmi_unregister_smi(master->intf);
+}
+
+static const struct acpi_device_id ipmi_bt_i2c_acpi_id[] = {
+	{"BTMA0001", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(acpi, ipmi_bt_i2c_acpi_id);
+
+static const struct i2c_device_id ipmi_bt_i2c_i2c_id[] = {
+	{"ipmi-bt-i2c", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, ipmi_bt_i2c_i2c_id);
+
+static struct i2c_driver ipmi_bt_i2c_driver = {
+	.driver = {
+		.name = "ipmi-bt-i2c",
+		.acpi_match_table = ipmi_bt_i2c_acpi_id,
+	},
+	.id_table = ipmi_bt_i2c_i2c_id,
+	.probe = ipmi_bt_i2c_probe,
+	.remove = ipmi_bt_i2c_remove,
+};
+module_i2c_driver(ipmi_bt_i2c_driver);
+
+MODULE_AUTHOR("Brendan Higgins <brendanhiggins@...gle.com>");
+MODULE_DESCRIPTION("IPMI Block Transfer over I2C.");
+MODULE_LICENSE("GPL v2");
-- 
2.14.0.rc1.383.gd1ce394fe2-goog

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