fsi: Add IBM I2C Responder virtual FSI master

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>
Link: https://lore.kernel.org/r/20230612195657.245125-14-eajames@linux.ibm.com
Signed-off-by: Joel Stanley <joel@jms.id.au>

4 files changed, 359 insertions, 0 deletions

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..61659c27a973
--- /dev/null
+++ b/drivers/fsi/fsi-master-i2cr.c
@@ -0,0 +1,316 @@
+// 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-i2cr.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/fsi_master_i2cr.h>
+
+#define I2CR_ADDRESS_CFAM(a)	((a) >> 2)
+#define I2CR_INITIAL_PARITY	true
+
+#define I2CR_STATUS_CMD		0x60002
+#define  I2CR_STATUS_ERR	 BIT_ULL(61)
+#define I2CR_ERROR_CMD		0x60004
+#define I2CR_LOG_CMD		0x60008
+
+static const u8 i2cr_cfam[] = {
+	0xc0, 0x02, 0x0d, 0xa6,
+	0x80, 0x01, 0x10, 0x02,
+	0x80, 0x01, 0x10, 0x02,
+	0x80, 0x01, 0x10, 0x02,
+	0x80, 0x01, 0x80, 0x52,
+	0x80, 0x01, 0x10, 0x02,
+	0x80, 0x01, 0x10, 0x02,
+	0x80, 0x01, 0x10, 0x02,
+	0x80, 0x01, 0x10, 0x02,
+	0x80, 0x01, 0x22, 0x2d,
+	0x00, 0x00, 0x00, 0x00,
+	0xde, 0xad, 0xc0, 0xde
+};
+
+static bool i2cr_check_parity32(u32 v, bool parity)
+{
+	u32 i;
+
+	for (i = 0; i < 32; ++i) {
+		if (v & (1u << i))
+			parity = !parity;
+	}
+
+	return parity;
+}
+
+static bool i2cr_check_parity64(u64 v)
+{
+	u32 i;
+	bool parity = I2CR_INITIAL_PARITY;
+
+	for (i = 0; i < 64; ++i) {
+		if (v & (1llu << i))
+			parity = !parity;
+	}
+
+	return parity;
+}
+
+static u32 i2cr_get_command(u32 address, bool parity)
+{
+	address <<= 1;
+
+	if (i2cr_check_parity32(address, parity))
+		address |= 1;
+
+	return address;
+}
+
+static int i2cr_transfer(struct i2c_client *client, u32 command, u64 *data)
+{
+	struct i2c_msg msgs[2];
+	int ret;
+
+	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(client, command, ret);
+
+	if (ret < 0)
+		return ret;
+
+	return -EIO;
+}
+
+static int i2cr_check_status(struct i2c_client *client)
+{
+	u64 status;
+	int ret;
+
+	ret = i2cr_transfer(client, I2CR_STATUS_CMD, &status);
+	if (ret)
+		return ret;
+
+	if (status & I2CR_STATUS_ERR) {
+		u32 buf[3] = { 0, 0, 0 };
+		u64 error;
+		u64 log;
+
+		i2cr_transfer(client, I2CR_ERROR_CMD, &error);
+		i2cr_transfer(client, I2CR_LOG_CMD, &log);
+
+		trace_i2cr_status_error(client, status, error, log);
+
+		buf[0] = I2CR_STATUS_CMD;
+		i2c_master_send(client, (const char *)buf, sizeof(buf));
+
+		buf[0] = I2CR_ERROR_CMD;
+		i2c_master_send(client, (const char *)buf, sizeof(buf));
+
+		buf[0] = I2CR_LOG_CMD;
+		i2c_master_send(client, (const char *)buf, sizeof(buf));
+
+		dev_err(&client->dev, "status:%016llx error:%016llx log:%016llx\n", status, error,
+			log);
+		return -EREMOTEIO;
+	}
+
+	trace_i2cr_status(client, status);
+	return 0;
+}
+
+int fsi_master_i2cr_read(struct fsi_master_i2cr *i2cr, u32 addr, u64 *data)
+{
+	u32 command = i2cr_get_command(addr, I2CR_INITIAL_PARITY);
+	int ret;
+
+	mutex_lock(&i2cr->lock);
+
+	ret = i2cr_transfer(i2cr->client, command, data);
+	if (ret)
+		goto unlock;
+
+	ret = i2cr_check_status(i2cr->client);
+	if (ret)
+		goto unlock;
+
+	trace_i2cr_read(i2cr->client, command, data);
+
+unlock:
+	mutex_unlock(&i2cr->lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(fsi_master_i2cr_read);
+
+int fsi_master_i2cr_write(struct fsi_master_i2cr *i2cr, u32 addr, u64 data)
+{
+	u32 buf[3] = { 0 };
+	int ret;
+
+	buf[0] = i2cr_get_command(addr, i2cr_check_parity64(data));
+	memcpy(&buf[1], &data, sizeof(data));
+
+	mutex_lock(&i2cr->lock);
+
+	ret = i2c_master_send(i2cr->client, (const char *)buf, sizeof(buf));
+	if (ret == sizeof(buf)) {
+		ret = i2cr_check_status(i2cr->client);
+		if (!ret)
+			trace_i2cr_write(i2cr->client, buf[0], data);
+	} else {
+		trace_i2cr_i2c_error(i2cr->client, buf[0], ret);
+
+		if (ret >= 0)
+			ret = -EIO;
+	}
+
+	mutex_unlock(&i2cr->lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(fsi_master_i2cr_write);
+
+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);
+	u64 data;
+	size_t i;
+	int ret;
+
+	if (link || id || (addr & 0xffff0000) || !(size == 1 || size == 2 || size == 4))
+		return -EINVAL;
+
+	/*
+	 * The I2CR doesn't have CFAM or FSI slave address space - only the
+	 * engines. In order for this to work with the FSI core, we need to
+	 * emulate at minimum the CFAM config table so that the appropriate
+	 * engines are discovered.
+	 */
+	if (addr < 0xc00) {
+		if (addr > sizeof(i2cr_cfam) - 4)
+			addr = (addr & 0x3) + (sizeof(i2cr_cfam) - 4);
+
+		memcpy(val, &i2cr_cfam[addr], size);
+		return 0;
+	}
+
+	ret = fsi_master_i2cr_read(i2cr, I2CR_ADDRESS_CFAM(addr), &data);
+	if (ret)
+		return ret;
+
+	/*
+	 * FSI core expects up to 4 bytes BE back, while I2CR replied with LE
+	 * bytes on the wire.
+	 */
+	for (i = 0; i < size; ++i)
+		((u8 *)val)[i] = ((u8 *)&data)[7 - i];
+
+	return 0;
+}
+
+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);
+	u64 data = 0;
+	size_t i;
+
+	if (link || id || (addr & 0xffff0000) || !(size == 1 || size == 2 || size == 4))
+		return -EINVAL;
+
+	/* I2CR writes to CFAM or FSI slave address are a successful no-op. */
+	if (addr < 0xc00)
+		return 0;
+
+	/*
+	 * FSI core passes up to 4 bytes BE, while the I2CR expects LE bytes on
+	 * the wire.
+	 */
+	for (i = 0; i < size; ++i)
+		((u8 *)&data)[7 - i] = ((u8 *)val)[i];
+
+	return fsi_master_i2cr_write(i2cr, I2CR_ADDRESS_CFAM(addr), data);
+}
+
+static void i2cr_release(struct device *dev)
+{
+	struct fsi_master_i2cr *i2cr = to_fsi_master_i2cr(to_fsi_master(dev));
+
+	of_node_put(dev->of_node);
+
+	kfree(i2cr);
+}
+
+static int i2cr_probe(struct i2c_client *client)
+{
+	struct fsi_master_i2cr *i2cr;
+	int ret;
+
+	i2cr = kzalloc(sizeof(*i2cr), GFP_KERNEL);
+	if (!i2cr)
+		return -ENOMEM;
+
+	/* Only one I2CR on any given I2C bus (fixed I2C device address) */
+	i2cr->master.idx = client->adapter->nr;
+	dev_set_name(&i2cr->master.dev, "i2cr%d", i2cr->master.idx);
+	i2cr->master.dev.parent = &client->dev;
+	i2cr->master.dev.of_node = of_node_get(dev_of_node(&client->dev));
+	i2cr->master.dev.release = i2cr_release;
+
+	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 void i2cr_remove(struct i2c_client *client)
+{
+	struct fsi_master_i2cr *i2cr = i2c_get_clientdata(client);
+
+	fsi_master_unregister(&i2cr->master);
+}
+
+static const struct of_device_id i2cr_ids[] = {
+	{ .compatible = "ibm,i2cr-fsi-master" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, i2cr_ids);
+
+static struct i2c_driver i2cr_driver = {
+	.probe_new = i2cr_probe,
+	.remove = i2cr_remove,
+	.driver = {
+		.name = "fsi-master-i2cr",
+		.of_match_table = i2cr_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/drivers/fsi/fsi-master-i2cr.h b/drivers/fsi/fsi-master-i2cr.h
new file mode 100644
index 000000000000..96636bf28cac
--- /dev/null
+++ b/drivers/fsi/fsi-master-i2cr.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (C) IBM Corporation 2023 */
+
+#ifndef DRIVERS_FSI_MASTER_I2CR_H
+#define DRIVERS_FSI_MASTER_I2CR_H
+
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+
+#include "fsi-master.h"
+
+struct i2c_client;
+
+struct fsi_master_i2cr {
+	struct fsi_master master;
+	struct mutex lock;	/* protect HW access */
+	struct i2c_client *client;
+};
+
+#define to_fsi_master_i2cr(m)	container_of(m, struct fsi_master_i2cr, master)
+
+int fsi_master_i2cr_read(struct fsi_master_i2cr *i2cr, u32 addr, u64 *data);
+int fsi_master_i2cr_write(struct fsi_master_i2cr *i2cr, u32 addr, u64 data);
+
+static inline bool is_fsi_master_i2cr(struct fsi_master *master)
+{
+	if (master->dev.parent && master->dev.parent->type == &i2c_client_type)
+		return true;
+
+	return false;
+}
+
+#endif /* DRIVERS_FSI_MASTER_I2CR_H */