/*
 * Copyright 2017 IBM Corp.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <asm/unaligned.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/cdev.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/fsi.h>
#include <linux/fsi-sbefifo.h>
#include <linux/fsi-occ.h>

#define OCC_SRAM_BYTES		4096
#define OCC_CMD_DATA_BYTES	4090
#define OCC_RESP_DATA_BYTES	4089

#define OCC_SRAM_CMD_ADDR	0xFFFBE000
#define OCC_SRAM_RSP_ADDR	0xFFFBF000

/*
 * Assume we don't have much FFDC, if we do we'll overflow and
 * fail the command. This needs to be big enough for simple
 * commands as well.
 */
#define OCC_SBE_STATUS_WORDS	32

#define OCC_TIMEOUT_MS		1000
#define OCC_CMD_IN_PRG_WAIT_MS	50

struct occ {
	struct platform_device *pdev;
	struct device *sbefifo;
	struct device dev;
	struct cdev cdev;
	struct mutex lock;
};

#define to_occ(x)	container_of((x), struct occ, mdev)

struct occ_response {
	u8 seq_no;
	u8 cmd_type;
	u8 return_status;
	__be16 data_length;
	u8 data[OCC_RESP_DATA_BYTES + 2];	/* two bytes checksum */
} __packed;

struct occ_client {
	struct occ *occ;
	struct mutex lock;
	size_t data_size;
	size_t read_offset;
	u8 *buffer;
};

#define to_client(x)	container_of((x), struct occ_client, xfr)

static int occ_open(struct inode *inode, struct file *file)
{
	struct occ_client *client = kzalloc(sizeof(*client), GFP_KERNEL);
	struct occ *occ = container_of(inode->i_cdev, struct occ, cdev);

	if (!client)
		return -ENOMEM;
	client->buffer = (u8 *)__get_free_page(GFP_KERNEL);
	if (!client->buffer) {
		kfree(client);
		return -ENOMEM;
	}
	client->occ = occ;
	mutex_init(&client->lock);
	file->private_data = client;

	/* We allocate a 1-page buffer, make sure it all fits */
	BUILD_BUG_ON((OCC_CMD_DATA_BYTES + 3) > PAGE_SIZE);
	BUILD_BUG_ON((OCC_RESP_DATA_BYTES + 7) > PAGE_SIZE);

	return 0;
}

static ssize_t occ_read(struct file *file, char __user *buf, size_t len,
			loff_t *offset)
{
	struct occ_client *client = file->private_data;
	ssize_t rc = 0;

	if (!client)
		return -ENODEV;
	if (len > OCC_SRAM_BYTES)
		return -EINVAL;

	mutex_lock(&client->lock);

	/* This should not be possible ... */
	if (WARN_ON_ONCE(client->read_offset > client->data_size)) {
		rc = -EIO;
		goto done;
	}

	/* Grab how much data we have to read */
	rc = min(len, client->data_size - client->read_offset);

	if (copy_to_user(buf, client->buffer + client->read_offset, rc))
		rc = -EFAULT;
	else
		client->read_offset += rc;
 done:
	mutex_unlock(&client->lock);

	return rc;
}

static ssize_t occ_write(struct file *file, const char __user *buf,
			 size_t len, loff_t *offset)
{
	struct occ_client *client = file->private_data;
	size_t rlen, data_length;
	u16 checksum = 0;
	ssize_t rc, i;
	u8 *cmd;

	if (!client)
		return -ENODEV;

	if (len > (OCC_CMD_DATA_BYTES + 3) || len < 3)
		return -EINVAL;

	mutex_lock(&client->lock);

	/* Construct the command */
	cmd = client->buffer;

	/* Sequence number (we could increment it and compare with the response) */
	cmd[0] = 1;

	/*
	 * Copy the user command (assume user data follows the occ command format)
	 *  byte 0  : command type
	 * bytes 1-2: data length (msb first)
	 * bytes 3-n: data
	 */
	if (copy_from_user(&cmd[1], buf, len)) {
		rc = -EFAULT;
		goto done;
	}

	/* Extract data length */
	data_length = (cmd[2] << 8) + cmd[3];
	if (data_length > OCC_CMD_DATA_BYTES) {
		rc = -EINVAL;
		goto done;
	}

	/* Calculate checksum */
	for (i = 0; i < data_length + 4; ++i)
		checksum += cmd[i];
	cmd[data_length + 4] = checksum >> 8;
	cmd[data_length + 5] = checksum & 0xFF;

	/* Submit command */
	rlen = PAGE_SIZE;
	rc = fsi_occ_submit(&client->occ->pdev->dev, cmd, data_length + 6, cmd, &rlen);
	if (rc)
		goto done;

	/* Set read tracking data */
	client->data_size = rlen;
	client->read_offset = 0;

	/* Done */
	rc = len;
 done:
	mutex_unlock(&client->lock);

	return rc;
}

static int occ_release(struct inode *inode, struct file *file)
{
	struct occ_client *client = file->private_data;

	free_page((unsigned long)client->buffer);
	kfree(client);

	return 0;
}

static const struct file_operations occ_fops = {
	.owner = THIS_MODULE,
	.open = occ_open,
	.read = occ_read,
	.write = occ_write,
	.release = occ_release,
};

static int occ_verify_checksum(struct occ_response *resp, u16 data_length)
{
	u16 checksum;
	/* Fetch the two bytes after the data for the checksum. */
	u16 checksum_resp = get_unaligned_be16(&resp->data[data_length]);
	u16 i;

	checksum = resp->seq_no;
	checksum += resp->cmd_type;
	checksum += resp->return_status;
	checksum += (data_length >> 8) + (data_length & 0xFF);

	for (i = 0; i < data_length; ++i)
		checksum += resp->data[i];

	if (checksum != checksum_resp)
		return -EBADMSG;

	return 0;
}

static int occ_getsram(struct device *sbefifo, u32 address, void *data,
		       ssize_t len)
{
	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
	size_t resp_len, resp_data_len;
	__be32 *resp, cmd[5];
	int rc;

	/*
	 * Magic sequence to do SBE getsram command. SBE will fetch data from
	 * specified SRAM address.
	 */
	cmd[0] = cpu_to_be32(0x5);
	cmd[1] = cpu_to_be32(SBEFIFO_CMD_GET_OCC_SRAM);
	cmd[2] = cpu_to_be32(1);
	cmd[3] = cpu_to_be32(address);
	cmd[4] = cpu_to_be32(data_len);

	resp_len = (data_len >> 2) + OCC_SBE_STATUS_WORDS;
	resp = kzalloc(resp_len << 2 , GFP_KERNEL);
	if (!resp)
		return -ENOMEM;

	rc = sbefifo_submit(sbefifo, cmd, 5, resp, &resp_len);
	if (rc)
		goto free;
	rc = sbefifo_parse_status(sbefifo, SBEFIFO_CMD_GET_OCC_SRAM,
				  resp, resp_len, &resp_len);
	if (rc)
		goto free;

	resp_data_len = be32_to_cpu(resp[resp_len - 1]);
	if (resp_data_len != data_len) {
		pr_err("occ: SRAM read expected %d bytes got %zd\n",
		       data_len, resp_data_len);
		rc = -EBADMSG;
	} else {
		memcpy(data, resp, len);
	}

free:
	/* Convert positive SBEI status */
	if (rc > 0) {
		pr_err("occ: SRAM read returned failure status: %08x\n", rc);
		rc = -EBADMSG;
	}
	kfree(resp);
	return rc;
}

static int occ_putsram(struct device *sbefifo, u32 address, const void *data,
		       ssize_t len)
{
	size_t cmd_len, buf_len, resp_len, resp_data_len;
	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
	__be32 *buf;
	int rc;

	/*
	 * We use the same buffer for command and response, make
	 * sure it's big enough
	 */
	resp_len = OCC_SBE_STATUS_WORDS;
	cmd_len = (data_len >> 2) + 5;
	buf_len = max(cmd_len, resp_len);
	buf = kzalloc(buf_len << 2, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	/*
	 * Magic sequence to do SBE putsram command. SBE will transfer
	 * data to specified SRAM address.
	 */
	buf[0] = cpu_to_be32(cmd_len);
	buf[1] = cpu_to_be32(SBEFIFO_CMD_PUT_OCC_SRAM);
	buf[2] = cpu_to_be32(1);
	buf[3] = cpu_to_be32(address);
	buf[4] = cpu_to_be32(data_len);

	memcpy(&buf[5], data, len);

	rc = sbefifo_submit(sbefifo, buf, cmd_len, buf, &resp_len);
	if (rc)
		goto free;
	rc = sbefifo_parse_status(sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
				  buf, resp_len, &resp_len);
	if (rc)
		goto free;

	if (resp_len != 1) {
		pr_err("occ: SRAM write response lenght invalid: %zd\n",
		       resp_len);
		rc = -EBADMSG;
	} else {
		resp_data_len = be32_to_cpu(buf[0]);
		if (resp_data_len != data_len) {
			pr_err("occ: SRAM write expected %d bytes got %zd\n",
			       data_len, resp_data_len);
			rc = -EBADMSG;
		}
	}
free:
	/* Convert positive SBEI status */
	if (rc > 0) {
		pr_err("occ: SRAM write returned failure status: %08x\n", rc);
		rc = -EBADMSG;
	}
	kfree(buf);
	return rc;
}

static int occ_trigger_attn(struct device *sbefifo)
{
	__be32 buf[OCC_SBE_STATUS_WORDS];
	size_t resp_len, resp_data_len;
	int rc;

	BUILD_BUG_ON(OCC_SBE_STATUS_WORDS < 7);
	resp_len = OCC_SBE_STATUS_WORDS;

	buf[0] = cpu_to_be32(0x5 + 0x2);        /* Chip-op length in words */
	buf[1] = cpu_to_be32(SBEFIFO_CMD_PUT_OCC_SRAM);
	buf[2] = cpu_to_be32(0x3);              /* Mode: Circular */
	buf[3] = cpu_to_be32(0x0);              /* Address: ignored in mode 3 */
	buf[4] = cpu_to_be32(0x8);              /* Data length in bytes */
	buf[5] = cpu_to_be32(0x20010000);       /* Trigger OCC attention */
	buf[6] = 0;

	rc = sbefifo_submit(sbefifo, buf, 7, buf, &resp_len);
	if (rc)
		goto error;
	rc = sbefifo_parse_status(sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
				  buf, resp_len, &resp_len);
	if (rc)
		goto error;

	if (resp_len != 1) {
		pr_err("occ: SRAM attn response lenght invalid: %zd\n",
		       resp_len);
		rc = -EBADMSG;
	} else {
		resp_data_len = be32_to_cpu(buf[0]);
		if (resp_data_len != 8) {
			pr_err("occ: SRAM attn expected 8 bytes got %zd\n",
			       resp_data_len);
			rc = -EBADMSG;
		}
	}
 error:
	/* Convert positive SBEI status */
	if (rc > 0) {
		pr_err("occ: SRAM attn returned failure status: %08x\n", rc);
		rc = -EBADMSG;
	}


	return rc;
}

int fsi_occ_submit(struct device *dev, const void *request, size_t req_len,
		   void *response, size_t *resp_len)
{
	const unsigned long timeout = msecs_to_jiffies(OCC_TIMEOUT_MS);
	const unsigned long wait_time = msecs_to_jiffies(OCC_CMD_IN_PRG_WAIT_MS);
	struct occ *occ = dev_get_drvdata(dev);
	struct occ_response *resp = response;
	struct device *sbefifo = occ->sbefifo;
	u16 resp_data_length;
	unsigned long start;
	int rc;

	if (!occ)
		return -ENODEV;
	if (*resp_len < 7) {
		dev_dbg(dev, "Bad resplen %zd\n", *resp_len);
		return -EINVAL;
	}

	mutex_lock(&occ->lock);
	if (!sbefifo)
		rc = -ENODEV;
	else
		rc = occ_putsram(sbefifo, OCC_SRAM_CMD_ADDR, request, req_len);
	if (rc)
		goto done;

	rc = occ_trigger_attn(sbefifo);
	if (rc)
		goto done;

	/* Read occ response header */
	start = jiffies;
	do {
		rc = occ_getsram(sbefifo, OCC_SRAM_RSP_ADDR, resp, 8);
		if (rc)
			goto done;

		if (resp->return_status == OCC_RESP_CMD_IN_PRG) {
			rc = -ETIMEDOUT;

			if (time_after(jiffies, start + timeout))
				break;

			set_current_state(TASK_UNINTERRUPTIBLE);
			schedule_timeout(wait_time);
		}
	} while (rc);

	/* Extract size of response data */
	resp_data_length = get_unaligned_be16(&resp->data_length);

	/* Message size is data length + 5 bytes header + 2 bytes checksum */
	if ((resp_data_length + 7) > *resp_len) {
		rc = -EMSGSIZE;
		goto done;
	}

	dev_dbg(dev, "resp_status=%02x resp_data_len=%d\n",
		resp->return_status, resp_data_length);

	/* Grab the rest */
	if (resp_data_length > 1) {
		/* already got 3 bytes resp, also need 2 bytes checksum */
		rc = occ_getsram(sbefifo, OCC_SRAM_RSP_ADDR + 8,
				 &resp->data[3], resp_data_length - 1);
		if (rc)
			goto done;
	}

	*resp_len = resp_data_length + 7;

	rc = occ_verify_checksum(resp, resp_data_length);
 done:
	mutex_unlock(&occ->lock);

	return rc;
}
EXPORT_SYMBOL_GPL(fsi_occ_submit);

static int occ_unregister_child(struct device *dev, void *data)
{
	struct platform_device *hwmon_dev = to_platform_device(dev);

	platform_device_unregister(hwmon_dev);

	return 0;
}

static void occ_free(struct device *dev)
{
	struct occ *occ = container_of(dev, struct occ, dev);

	put_device(&occ->pdev->dev);
	kfree(occ);
}

static int occ_probe(struct platform_device *pdev)
{
	int rc, didx;
	struct occ *occ;
	struct platform_device *hwmon_dev;
	struct platform_device_info hwmon_dev_info = {
		.parent = &pdev->dev,
		.name = "occ-hwmon",
	};

	occ = kzalloc(sizeof(*occ), GFP_KERNEL);
	if (!occ)
		return -ENOMEM;

	/* Grab a reference to the device (parent of our cdev), we'll drop it later */
	if (!get_device(&pdev->dev)) {
		kfree(occ);
		return -ENODEV;
	}

	occ->pdev = pdev;
	occ->sbefifo = pdev->dev.parent;
	platform_set_drvdata(pdev, occ);
	mutex_init(&occ->lock);

	/* Create chardev for userspace access */
	occ->dev.type = &fsi_cdev_type;
	occ->dev.parent = &pdev->dev;
	occ->dev.release = occ_free;
	device_initialize(&occ->dev);

	/* Allocate a minor in the FSI space */
	rc = fsi_get_new_minor(sbefifo_get_fsidev(occ->sbefifo),
			       fsi_dev_occ, &occ->dev.devt, &didx);
	if (rc)
		goto err;

	/*
	 * If we have a device node, try to use the "reg" property as our
	 * device index, otherwise use didx which is our chip-id on simple
	 * platforms.
	 */
	if (dev_of_node(&pdev->dev)) {
		u32 reg;
		rc = of_property_read_u32(dev_of_node(&pdev->dev), "reg", &reg);
		if (!rc)
			didx = reg;
	}

	dev_set_name(&occ->dev, "occ%d", didx);
	cdev_init(&occ->cdev, &occ_fops);
	rc = cdev_device_add(&occ->cdev, &occ->dev);
	if (rc) {
		dev_err(&pdev->dev, "Error %d creating char device %s\n",
			rc, dev_name(&occ->dev));
		goto err_free_minor;
	}

	hwmon_dev_info.id = didx;
	hwmon_dev = platform_device_register_full(&hwmon_dev_info);
	if (!hwmon_dev)
		dev_warn(&pdev->dev, "failed to create hwmon device\n");

	return 0;
 err_free_minor:
	fsi_free_minor(occ->dev.devt);
 err:
	put_device(&occ->dev);
	return rc;
}

static int occ_remove(struct platform_device *pdev)
{
	struct occ *occ = platform_get_drvdata(pdev);

	/* The parent is potentially going away, so we must not reference it anymore */
	mutex_lock(&occ->lock);
	occ->sbefifo = NULL;
	mutex_unlock(&occ->lock);

	cdev_device_del(&occ->cdev, &occ->dev);
	fsi_free_minor(occ->dev.devt);

	device_for_each_child(&pdev->dev, NULL, occ_unregister_child);

	put_device(&occ->dev);

	return 0;
}

static const struct of_device_id occ_match[] = {
	{ .compatible = "ibm,p9-occ" },
	{ },
};

static struct platform_driver occ_driver = {
	.driver = {
		.name = "occ",
		.of_match_table	= occ_match,
	},
	.probe	= occ_probe,
	.remove = occ_remove,
};

static int occ_init(void)
{
	return platform_driver_register(&occ_driver);
}

static void occ_exit(void)
{
	platform_driver_unregister(&occ_driver);
}

module_init(occ_init);
module_exit(occ_exit);

MODULE_AUTHOR("Eddie James <eajames@us.ibm.com>");
MODULE_DESCRIPTION("BMC P9 OCC driver");
MODULE_LICENSE("GPL");