[PATCH 2/2] fsi: Add IBM I2C Responder virtual FSI master

[Eddie James <eajames@linux.ibm.com>]

The I2C Responder (I2CR) is an I2C device that translates I2C commands
to CFAM or SCOM operations, effectively implementing an FSI master and
bus.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/fsi/Kconfig                    |   9 +
 drivers/fsi/Makefile                   |   1 +
 drivers/fsi/fsi-master-i2cr.c          | 225 +++++++++++++++++++++++++
 include/trace/events/fsi_master_i2cr.h |  96 +++++++++++
 4 files changed, 331 insertions(+)
 create mode 100644 drivers/fsi/fsi-master-i2cr.c
 create mode 100644 include/trace/events/fsi_master_i2cr.h

diff --git a/drivers/fsi/Kconfig b/drivers/fsi/Kconfig
index e6668a869913..999be82720c5 100644
--- a/drivers/fsi/Kconfig
+++ b/drivers/fsi/Kconfig
@@ -62,6 +62,15 @@ config FSI_MASTER_ASPEED
 
 	 Enable it for your BMC kernel in an OpenPower or IBM Power system.
 
+config FSI_MASTER_I2CR
+	tristate "IBM I2C Responder virtual FSI master"
+	depends on I2C
+	help
+	  This option enables a virtual FSI master in order to access a CFAM
+	  behind an IBM I2C Responder (I2CR) chip. The I2CR is an I2C device
+	  that translates I2C commands to CFAM or SCOM operations, effectively
+	  implementing an FSI master and bus.
+
 config FSI_SCOM
 	tristate "SCOM FSI client device driver"
 	help
diff --git a/drivers/fsi/Makefile b/drivers/fsi/Makefile
index da218a1ad8e1..34dbaa1c452e 100644
--- a/drivers/fsi/Makefile
+++ b/drivers/fsi/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_FSI) += fsi-core.o
 obj-$(CONFIG_FSI_MASTER_HUB) += fsi-master-hub.o
 obj-$(CONFIG_FSI_MASTER_ASPEED) += fsi-master-aspeed.o
 obj-$(CONFIG_FSI_MASTER_GPIO) += fsi-master-gpio.o
+obj-$(CONFIG_FSI_MASTER_I2CR) += fsi-master-i2cr.o
 obj-$(CONFIG_FSI_MASTER_AST_CF) += fsi-master-ast-cf.o
 obj-$(CONFIG_FSI_SCOM) += fsi-scom.o
 obj-$(CONFIG_FSI_SBEFIFO) += fsi-sbefifo.o
diff --git a/drivers/fsi/fsi-master-i2cr.c b/drivers/fsi/fsi-master-i2cr.c
new file mode 100644
index 000000000000..d19ac96c0a83
--- /dev/null
+++ b/drivers/fsi/fsi-master-i2cr.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) IBM Corporation 2023 */
+
+#include <linux/device.h>
+#include <linux/fsi.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/mutex.h>
+
+#include "fsi-master.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/fsi_master_i2cr.h>
+
+#define I2CR_ADDRESS_CFAM(a)	((a) >> 2)
+#define I2CR_STATUS		0x30001
+#define  I2CR_STATUS_ERR	 BIT_ULL(61)
+#define I2CR_ERROR		0x30002
+
+struct fsi_master_i2cr {
+	struct fsi_master master;
+	struct mutex lock;	/* protect HW access */
+	struct i2c_client *client;
+};
+
+static bool i2cr_check_parity(u32 v, bool parity)
+{
+	u32 i;
+
+	for (i = 0; i < 32; ++i) {
+		if (v & (1 << i))
+			parity = !parity;
+	}
+
+	return parity;
+}
+
+static __be32 i2cr_get_command(u32 address, bool parity)
+{
+	__be32 command;
+
+	address <<= 1;
+
+	if (i2cr_check_parity(address, parity))
+		address |= 1;
+
+	command = cpu_to_be32(address);
+	trace_i2cr_command((__force uint32_t)command);
+
+	return command;
+}
+
+static int i2cr_transfer(struct i2c_client *client, u32 address, __be64 *data)
+{
+	struct i2c_msg msgs[2];
+	__be32 command;
+	int ret;
+
+	command = i2cr_get_command(address, true);
+	msgs[0].addr = client->addr;
+	msgs[0].flags = 0;
+	msgs[0].len = sizeof(command);
+	msgs[0].buf = (__u8 *)&command;
+	msgs[1].addr = client->addr;
+	msgs[1].flags = I2C_M_RD;
+	msgs[1].len = sizeof(*data);
+	msgs[1].buf = (__u8 *)data;
+
+	ret = i2c_transfer(client->adapter, msgs, 2);
+	if (ret == 2)
+		return 0;
+
+	trace_i2cr_i2c_error(ret);
+
+	if (ret < 0)
+		return ret;
+
+	return -EIO;
+}
+
+static int i2cr_check_status(struct i2c_client *client)
+{
+	__be64 status_be = 0;
+	u64 status;
+	int ret;
+
+	ret = i2cr_transfer(client, I2CR_STATUS, &status_be);
+	if (ret)
+		return ret;
+
+	status = be64_to_cpu(status_be);
+	if (status & I2CR_STATUS_ERR) {
+		__be64 error_be = 0;
+		u64 error;
+
+		i2cr_transfer(client, I2CR_ERROR, &error_be);
+		error = be64_to_cpu(error_be);
+		trace_i2cr_status_error(status, error);
+		dev_err(&client->dev, "status:%016llx error:%016llx\n", status, error);
+		return -EREMOTEIO;
+	}
+
+	trace_i2cr_status(status);
+	return 0;
+}
+
+static int i2cr_read(struct fsi_master *master, int link, uint8_t id, uint32_t addr, void *val,
+		     size_t size)
+{
+	struct fsi_master_i2cr *i2cr = container_of(master, struct fsi_master_i2cr, master);
+	__be64 data = 0;
+	int ret;
+
+	if (link || id || (addr & 0xffff0000) || !size || size > 4 || size == 3)
+		return -EINVAL;
+
+	mutex_lock(&i2cr->lock);
+
+	ret = i2cr_transfer(i2cr->client, I2CR_ADDRESS_CFAM(addr), &data);
+	if (ret)
+		goto unlock;
+
+	ret = i2cr_check_status(i2cr->client);
+	if (ret)
+		goto unlock;
+
+	trace_i2cr_read(addr, size, (__force uint32_t)data);
+	memcpy(val, &data, size);
+
+unlock:
+	mutex_unlock(&i2cr->lock);
+	return ret;
+}
+
+static int i2cr_write(struct fsi_master *master, int link, uint8_t id, uint32_t addr,
+		      const void *val, size_t size)
+{
+	struct fsi_master_i2cr *i2cr = container_of(master, struct fsi_master_i2cr, master);
+	__be32 data[3];
+	int ret;
+
+	if (link || id || (addr & 0xffff0000) || !size || size > 4 || size == 3)
+		return -EINVAL;
+
+	data[1] = 0;
+	memcpy(&data[1], val, size);
+	data[0] = i2cr_get_command(I2CR_ADDRESS_CFAM(addr),
+				   i2cr_check_parity((__force u32)data[1], true));
+	data[2] = 0;
+
+	mutex_lock(&i2cr->lock);
+
+	ret = i2c_master_send(i2cr->client, (const char *)data, sizeof(data));
+	if (ret == sizeof(data)) {
+		ret = i2cr_check_status(i2cr->client);
+		if (!ret)
+			trace_i2cr_write(addr, size, (__force uint32_t)data[1]);
+	} else {
+		trace_i2cr_i2c_error(ret);
+
+		if (ret >= 0)
+			ret = -EIO;
+	}
+
+	mutex_unlock(&i2cr->lock);
+	return ret;
+}
+
+static int i2cr_probe(struct i2c_client *client)
+{
+	struct fsi_master_i2cr *i2cr;
+	int ret;
+
+	i2cr = devm_kzalloc(&client->dev, sizeof(*i2cr), GFP_KERNEL);
+	if (!i2cr)
+		return -ENOMEM;
+
+	i2cr->master.dev.parent = &client->dev;
+	i2cr->master.dev.of_node = of_node_get(dev_of_node(&client->dev));
+
+	i2cr->master.n_links = 1;
+	i2cr->master.read = i2cr_read;
+	i2cr->master.write = i2cr_write;
+
+	mutex_init(&i2cr->lock);
+	i2cr->client = client;
+
+	ret = fsi_master_register(&i2cr->master);
+	if (ret)
+		return ret;
+
+	i2c_set_clientdata(client, i2cr);
+	return 0;
+}
+
+static int i2cr_remove(struct i2c_client *client)
+{
+	struct fsi_master_i2cr *i2cr = i2c_get_clientdata(client);
+
+	fsi_master_unregister(&i2cr->master);
+
+	return 0;
+}
+
+static const struct of_device_id i2cr_i2c_ids[] = {
+	{ .compatible = "ibm,i2cr", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, i2cr_i2c_ids);
+
+static struct i2c_driver i2cr_driver = {
+	.probe_new = i2cr_probe,
+	.remove = i2cr_remove,
+	.driver = {
+		.name = "i2cr",
+		.of_match_table = i2cr_i2c_ids,
+	},
+};
+
+module_i2c_driver(i2cr_driver)
+
+MODULE_AUTHOR("Eddie James <eajames@linux.ibm.com>");
+MODULE_DESCRIPTION("IBM I2C Responder virtual FSI master driver");
+MODULE_LICENSE("GPL");
diff --git a/include/trace/events/fsi_master_i2cr.h b/include/trace/events/fsi_master_i2cr.h
new file mode 100644
index 000000000000..7b53c6a35bc7
--- /dev/null
+++ b/include/trace/events/fsi_master_i2cr.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM fsi_master_i2cr
+
+#if !defined(_TRACE_FSI_MASTER_I2CR_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_FSI_MASTER_I2CR_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(i2cr_command,
+	TP_PROTO(uint32_t command),
+	TP_ARGS(command),
+	TP_STRUCT__entry(
+		__field(uint32_t,	command)
+	),
+	TP_fast_assign(
+		__entry->command = command;
+	),
+	TP_printk("command:%08x", __entry->command)
+);
+
+TRACE_EVENT(i2cr_i2c_error,
+	TP_PROTO(int rc),
+	TP_ARGS(rc),
+	TP_STRUCT__entry(
+		__field(int,	rc)
+	),
+	TP_fast_assign(
+		__entry->rc = rc;
+	),
+	TP_printk("rc:%d", __entry->rc)
+);
+
+TRACE_EVENT(i2cr_read,
+	TP_PROTO(uint32_t addr, size_t size, uint64_t result),
+	TP_ARGS(addr, size, result),
+	TP_STRUCT__entry(
+		__field(uint32_t,	addr)
+		__field(size_t,		size)
+		__field(uint64_t,	result)
+	),
+	TP_fast_assign(
+		__entry->addr = addr;
+		__entry->size = size;
+		__entry->result = result;
+	),
+	TP_printk("addr:%08x size:%zu result:%016llx", __entry->addr, __entry->size,
+		  __entry->result)
+);
+
+TRACE_EVENT(i2cr_status,
+	TP_PROTO(uint64_t status),
+	TP_ARGS(status),
+	TP_STRUCT__entry(
+		__field(uint32_t,	status)
+	),
+	TP_fast_assign(
+		__entry->status = status >> 32;
+	),
+	TP_printk("status:%08x", __entry->status)
+);
+
+TRACE_EVENT(i2cr_status_error,
+	TP_PROTO(uint64_t status, uint64_t error),
+	TP_ARGS(status, error),
+	TP_STRUCT__entry(
+		__field(uint64_t,	error)
+		__field(uint32_t,	status)
+	),
+	TP_fast_assign(
+		__entry->error = error;
+		__entry->status = status >> 32;
+	),
+	TP_printk("status:%08x error:%016llx", __entry->status, __entry->error)
+);
+
+TRACE_EVENT(i2cr_write,
+	TP_PROTO(uint32_t addr, uint32_t val, size_t size),
+	TP_ARGS(addr, val, size),
+	TP_STRUCT__entry(
+		__field(uint32_t,	addr)
+		__field(uint32_t,	val)
+		__field(size_t,		size)
+	),
+	TP_fast_assign(
+		__entry->addr = addr;
+		__entry->val = val;
+		__entry->size = size;
+	),
+	TP_printk("addr:%08x val:%08x size:%zu", __entry->addr, __entry->val, __entry->size)
+);
+
+#endif
+
+#include <trace/define_trace.h>
-- 
2.31.1