drivers/fsi: Add SCOM FSI client device driver

Create a simple SCOM engine device driver that reads and writes
its control registers via an FSI bus.

Includes changes from Edward A. James <[e-mail]>.

Signed-off-by: Christopher Bostic <[e-mail]>
Signed-off-by: Joel Stanley <[e-mail]>
Signed-off-by: Edward A. James <[e-mail]>
Signed-off-by: Jeremy Kerr <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/fsi/Kconfig

···
 	---help---
 	This option enables a FSI master driver using GPIO lines.
 
+config FSI_SCOM
+	tristate "SCOM FSI client device driver"
+	---help---
+	This option enables an FSI based SCOM device driver.
+
 endif
 
 endmenu

drivers/fsi/Makefile

···
 
 obj-$(CONFIG_FSI) += fsi-core.o
 obj-$(CONFIG_FSI_MASTER_GPIO) += fsi-master-gpio.o
+obj-$(CONFIG_FSI_SCOM) += fsi-scom.o

drivers/fsi/fsi-scom.c

···
+/*
+ * SCOM FSI Client device driver
+ *
+ * Copyright (C) IBM Corporation 2016
+ *
+ * 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
+ * MERGCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/fsi.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
+#include <linux/delay.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+#include <linux/miscdevice.h>
+#include <linux/list.h>
+#include <linux/idr.h>
+
+#define FSI_ENGID_SCOM		0x5
+
+#define SCOM_FSI2PIB_DELAY	50
+
+/* SCOM engine register set */
+#define SCOM_DATA0_REG		0x00
+#define SCOM_DATA1_REG		0x04
+#define SCOM_CMD_REG		0x08
+#define SCOM_RESET_REG		0x1C
+
+#define SCOM_RESET_CMD		0x80000000
+#define SCOM_WRITE_CMD		0x80000000
+
+struct scom_device {
+	struct list_head link;
+	struct fsi_device *fsi_dev;
+	struct miscdevice mdev;
+	char	name[32];
+	int idx;
+};
+
+#define to_scom_dev(x)		container_of((x), struct scom_device, mdev)
+
+static struct list_head scom_devices;
+
+static DEFINE_IDA(scom_ida);
+
+static int put_scom(struct scom_device *scom_dev, uint64_t value,
+			uint32_t addr)
+{
+	int rc;
+	uint32_t data;
+
+	data = cpu_to_be32(SCOM_RESET_CMD);
+	rc = fsi_device_write(scom_dev->fsi_dev, SCOM_RESET_REG, &data,
+				sizeof(uint32_t));
+	if (rc)
+		return rc;
+
+	data = cpu_to_be32((value >> 32) & 0xffffffff);
+	rc = fsi_device_write(scom_dev->fsi_dev, SCOM_DATA0_REG, &data,
+				sizeof(uint32_t));
+	if (rc)
+		return rc;
+
+	data = cpu_to_be32(value & 0xffffffff);
+	rc = fsi_device_write(scom_dev->fsi_dev, SCOM_DATA1_REG, &data,
+				sizeof(uint32_t));
+	if (rc)
+		return rc;
+
+	data = cpu_to_be32(SCOM_WRITE_CMD | addr);
+	return fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
+				sizeof(uint32_t));
+}
+
+static int get_scom(struct scom_device *scom_dev, uint64_t *value,
+			uint32_t addr)
+{
+	uint32_t result, data;
+	int rc;
+
+	*value = 0ULL;
+	data = cpu_to_be32(addr);
+	rc = fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
+				sizeof(uint32_t));
+	if (rc)
+		return rc;
+
+	rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA0_REG, &result,
+				sizeof(uint32_t));
+	if (rc)
+		return rc;
+
+	*value |= (uint64_t)cpu_to_be32(result) << 32;
+	rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA1_REG, &result,
+				sizeof(uint32_t));
+	if (rc)
+		return rc;
+
+	*value |= cpu_to_be32(result);
+
+	return 0;
+}
+
+static ssize_t scom_read(struct file *filep, char __user *buf, size_t len,
+			loff_t *offset)
+{
+	int rc;
+	struct miscdevice *mdev =
+				(struct miscdevice *)filep->private_data;
+	struct scom_device *scom = to_scom_dev(mdev);
+	struct device *dev = &scom->fsi_dev->dev;
+	uint64_t val;
+
+	if (len != sizeof(uint64_t))
+		return -EINVAL;
+
+	rc = get_scom(scom, &val, *offset);
+	if (rc) {
+		dev_dbg(dev, "get_scom fail:%d\n", rc);
+		return rc;
+	}
+
+	rc = copy_to_user(buf, &val, len);
+	if (rc)
+		dev_dbg(dev, "copy to user failed:%d\n", rc);
+
+	return rc ? rc : len;
+}
+
+static ssize_t scom_write(struct file *filep, const char __user *buf,
+			size_t len, loff_t *offset)
+{
+	int rc;
+	struct miscdevice *mdev = filep->private_data;
+	struct scom_device *scom = to_scom_dev(mdev);
+	struct device *dev = &scom->fsi_dev->dev;
+	uint64_t val;
+
+	if (len != sizeof(uint64_t))
+		return -EINVAL;
+
+	rc = copy_from_user(&val, buf, len);
+	if (rc) {
+		dev_dbg(dev, "copy from user failed:%d\n", rc);
+		return -EINVAL;
+	}
+
+	rc = put_scom(scom, val, *offset);
+	if (rc) {
+		dev_dbg(dev, "put_scom failed with:%d\n", rc);
+		return rc;
+	}
+
+	return len;
+}
+
+static loff_t 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 const struct file_operations scom_fops = {
+	.owner	= THIS_MODULE,
+	.llseek	= scom_llseek,
+	.read	= scom_read,
+	.write	= scom_write,
+};
+
+static int scom_probe(struct device *dev)
+{
+	struct fsi_device *fsi_dev = to_fsi_dev(dev);
+	struct scom_device *scom;
+
+	scom = devm_kzalloc(dev, sizeof(*scom), GFP_KERNEL);
+	if (!scom)
+		return -ENOMEM;
+
+	scom->idx = ida_simple_get(&scom_ida, 1, INT_MAX, GFP_KERNEL);
+	snprintf(scom->name, sizeof(scom->name), "scom%d", scom->idx);
+	scom->fsi_dev = fsi_dev;
+	scom->mdev.minor = MISC_DYNAMIC_MINOR;
+	scom->mdev.fops = &scom_fops;
+	scom->mdev.name = scom->name;
+	scom->mdev.parent = dev;
+	list_add(&scom->link, &scom_devices);
+
+	return misc_register(&scom->mdev);
+}
+
+static int scom_remove(struct device *dev)
+{
+	struct scom_device *scom, *scom_tmp;
+	struct fsi_device *fsi_dev = to_fsi_dev(dev);
+
+	list_for_each_entry_safe(scom, scom_tmp, &scom_devices, link) {
+		if (scom->fsi_dev == fsi_dev) {
+			list_del(&scom->link);
+			ida_simple_remove(&scom_ida, scom->idx);
+			misc_deregister(&scom->mdev);
+		}
+	}
+
+	return 0;
+}
+
+static struct fsi_device_id scom_ids[] = {
+	{
+		.engine_type = FSI_ENGID_SCOM,
+		.version = FSI_VERSION_ANY,
+	},
+	{ 0 }
+};
+
+static struct fsi_driver scom_drv = {
+	.id_table = scom_ids,
+	.drv = {
+		.name = "scom",
+		.bus = &fsi_bus_type,
+		.probe = scom_probe,
+		.remove = scom_remove,
+	}
+};
+
+static int scom_init(void)
+{
+	INIT_LIST_HEAD(&scom_devices);
+	return fsi_driver_register(&scom_drv);
+}
+
+static void scom_exit(void)
+{
+	struct list_head *pos;
+	struct scom_device *scom;
+
+	list_for_each(pos, &scom_devices) {
+		scom = list_entry(pos, struct scom_device, link);
+		misc_deregister(&scom->mdev);
+		devm_kfree(&scom->fsi_dev->dev, scom);
+	}
+	fsi_driver_unregister(&scom_drv);
+}
+
+module_init(scom_init);
+module_exit(scom_exit);
+MODULE_LICENSE("GPL");