fsi: Add I2C Responder SCOM driver

The I2CR has the capability to directly perform SCOM operations,
circumventing the need to drive the FSI2PIB engine. Add a new
driver to perform SCOM operations through the I2CR.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20230612195657.245125-15-eajames@linux.ibm.com
Signed-off-by: Joel Stanley <joel@jms.id.au>

drivers/fsi/Kconfig

@@ -94,4 +94,12 @@ config FSI_OCC
 	provide the raw sensor data as well as perform thermal and power
 	management on the system.
 
+config I2CR_SCOM
+	tristate "IBM I2C Responder SCOM driver"
+	depends on FSI_MASTER_I2CR
+	help
+	  This option enables an I2C Responder based SCOM device driver. The
+	  I2CR has the capability to directly perform SCOM operations instead
+	  of using the FSI2PIB engine.
+
 endif

drivers/fsi/Makefile

@@ -9,3 +9,4 @@ obj-$(CONFIG_FSI_MASTER_AST_CF) += fsi-master-ast-cf.o
 obj-$(CONFIG_FSI_SCOM) += fsi-scom.o
 obj-$(CONFIG_FSI_SBEFIFO) += fsi-sbefifo.o
 obj-$(CONFIG_FSI_OCC) += fsi-occ.o
+obj-$(CONFIG_I2CR_SCOM) += i2cr-scom.o

drivers/fsi/i2cr-scom.c

@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) IBM Corporation 2023 */
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/fsi.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+
+#include "fsi-master-i2cr.h"
+#include "fsi-slave.h"
+
+struct i2cr_scom {
+	struct device dev;
+	struct cdev cdev;
+	struct fsi_master_i2cr *i2cr;
+};
+
+static loff_t i2cr_scom_llseek(struct file *file, loff_t offset, int whence)
+{
+	switch (whence) {
+	case SEEK_CUR:
+		break;
+	case SEEK_SET:
+		file->f_pos = offset;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return offset;
+}
+
+static ssize_t i2cr_scom_read(struct file *filep, char __user *buf, size_t len, loff_t *offset)
+{
+	struct i2cr_scom *scom = filep->private_data;
+	u64 data;
+	int ret;
+
+	if (len != sizeof(data))
+		return -EINVAL;
+
+	ret = fsi_master_i2cr_read(scom->i2cr, (u32)*offset, &data);
+	if (ret)
+		return ret;
+
+	ret = copy_to_user(buf, &data, len);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t i2cr_scom_write(struct file *filep, const char __user *buf, size_t len,
+			       loff_t *offset)
+{
+	struct i2cr_scom *scom = filep->private_data;
+	u64 data;
+	int ret;
+
+	if (len != sizeof(data))
+		return -EINVAL;
+
+	ret = copy_from_user(&data, buf, len);
+	if (ret)
+		return ret;
+
+	ret = fsi_master_i2cr_write(scom->i2cr, (u32)*offset, data);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static const struct file_operations i2cr_scom_fops = {
+	.owner		= THIS_MODULE,
+	.open		= simple_open,
+	.llseek		= i2cr_scom_llseek,
+	.read		= i2cr_scom_read,
+	.write		= i2cr_scom_write,
+};
+
+static int i2cr_scom_probe(struct device *dev)
+{
+	struct fsi_device *fsi_dev = to_fsi_dev(dev);
+	struct i2cr_scom *scom;
+	int didx;
+	int ret;
+
+	if (!is_fsi_master_i2cr(fsi_dev->slave->master))
+		return -ENODEV;
+
+	scom = devm_kzalloc(dev, sizeof(*scom), GFP_KERNEL);
+	if (!scom)
+		return -ENOMEM;
+
+	scom->i2cr = to_fsi_master_i2cr(fsi_dev->slave->master);
+	dev_set_drvdata(dev, scom);
+
+	scom->dev.type = &fsi_cdev_type;
+	scom->dev.parent = dev;
+	device_initialize(&scom->dev);
+
+	ret = fsi_get_new_minor(fsi_dev, fsi_dev_scom, &scom->dev.devt, &didx);
+	if (ret)
+		return ret;
+
+	dev_set_name(&scom->dev, "scom%d", didx);
+	cdev_init(&scom->cdev, &i2cr_scom_fops);
+	ret = cdev_device_add(&scom->cdev, &scom->dev);
+	if (ret)
+		fsi_free_minor(scom->dev.devt);
+
+	return ret;
+}
+
+static int i2cr_scom_remove(struct device *dev)
+{
+	struct i2cr_scom *scom = dev_get_drvdata(dev);
+
+	cdev_device_del(&scom->cdev, &scom->dev);
+	fsi_free_minor(scom->dev.devt);
+
+	return 0;
+}
+
+static const struct of_device_id i2cr_scom_of_ids[] = {
+	{ .compatible = "ibm,i2cr-scom" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, i2cr_scom_of_ids);
+
+static const struct fsi_device_id i2cr_scom_ids[] = {
+	{ 0x5, FSI_VERSION_ANY },
+	{ }
+};
+
+static struct fsi_driver i2cr_scom_driver = {
+	.id_table = i2cr_scom_ids,
+	.drv = {
+		.name = "i2cr_scom",
+		.bus = &fsi_bus_type,
+		.of_match_table = i2cr_scom_of_ids,
+		.probe = i2cr_scom_probe,
+		.remove = i2cr_scom_remove,
+	}
+};
+
+module_fsi_driver(i2cr_scom_driver);
+
+MODULE_AUTHOR("Eddie James <eajames@linux.ibm.com>");
+MODULE_DESCRIPTION("IBM I2C Responder SCOM driver");
+MODULE_LICENSE("GPL");