// SPDX-License-Identifier: GPL-2.0

#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/fsi-sbefifo.h>
#include <linux/gfp.h>
#include <linux/idr.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/miscdevice.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/fsi-occ.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <asm/unaligned.h>

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

#define OCC_P9_SRAM_CMD_ADDR	0xFFFBE000
#define OCC_P9_SRAM_RSP_ADDR	0xFFFBF000

#define OCC_P10_SRAM_CMD_ADDR	0xFFFFD000
#define OCC_P10_SRAM_RSP_ADDR	0xFFFFE000

#define OCC_P10_SRAM_MODE	0x58	/* Normal mode, OCB channel 2 */

#define OCC_TIMEOUT_MS		1000
#define OCC_CMD_IN_PRG_WAIT_MS	50

enum versions { occ_p9, occ_p10 };

struct occ {
	struct device *dev;
	struct device *sbefifo;
	char name[32];
	int idx;
	u8 sequence_number;
	void *buffer;
	void *client_buffer;
	size_t client_buffer_size;
	size_t client_response_size;
	enum versions version;
	struct miscdevice mdev;
	struct mutex occ_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 DEFINE_IDA(occ_ida);

static int occ_open(struct inode *inode, struct file *file)
{
	struct occ_client *client = kzalloc(sizeof(*client), GFP_KERNEL);
	struct miscdevice *mdev = file->private_data;
	struct occ *occ = to_occ(mdev);

	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;
	get_device(occ->dev);

	/* 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;
	ssize_t rc;
	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;

	/*
	 * 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;
	}

	/* Submit command; 4 bytes before the data and 2 bytes after */
	rlen = PAGE_SIZE;
	rc = fsi_occ_submit(client->occ->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;

	put_device(client->occ->dev);
	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 void occ_save_ffdc(struct occ *occ, __be32 *resp, size_t parsed_len,
			  size_t resp_len)
{
	if (resp_len > parsed_len) {
		size_t dh = resp_len - parsed_len;
		size_t ffdc_len = (dh - 1) * 4; /* SBE words are four bytes */
		__be32 *ffdc = &resp[parsed_len];

		if (ffdc_len > occ->client_buffer_size)
			ffdc_len = occ->client_buffer_size;

		memcpy(occ->client_buffer, ffdc, ffdc_len);
		occ->client_response_size = ffdc_len;
	}
}

static int occ_verify_checksum(struct occ *occ, struct occ_response *resp,
			       u16 data_length)
{
	/* Fetch the two bytes after the data for the checksum. */
	u16 checksum_resp = get_unaligned_be16(&resp->data[data_length]);
	u16 checksum;
	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) {
		dev_err(occ->dev, "Bad checksum: %04x!=%04x\n", checksum,
			checksum_resp);
		return -EBADMSG;
	}

	return 0;
}

static int occ_getsram(struct occ *occ, u32 offset, void *data, ssize_t len)
{
	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
	size_t cmd_len, parsed_len, resp_data_len;
	size_t resp_len = OCC_MAX_RESP_WORDS;
	__be32 *resp = occ->buffer;
	__be32 cmd[6];
	int idx = 0, rc;

	/*
	 * Magic sequence to do SBE getsram command. SBE will fetch data from
	 * specified SRAM address.
	 */
	switch (occ->version) {
	default:
	case occ_p9:
		cmd_len = 5;
		cmd[2] = cpu_to_be32(1);	/* Normal mode */
		cmd[3] = cpu_to_be32(OCC_P9_SRAM_RSP_ADDR + offset);
		break;
	case occ_p10:
		idx = 1;
		cmd_len = 6;
		cmd[2] = cpu_to_be32(OCC_P10_SRAM_MODE);
		cmd[3] = 0;
		cmd[4] = cpu_to_be32(OCC_P10_SRAM_RSP_ADDR + offset);
		break;
	}

	cmd[0] = cpu_to_be32(cmd_len);
	cmd[1] = cpu_to_be32(SBEFIFO_CMD_GET_OCC_SRAM);
	cmd[4 + idx] = cpu_to_be32(data_len);

	rc = sbefifo_submit(occ->sbefifo, cmd, cmd_len, resp, &resp_len);
	if (rc)
		return rc;

	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_GET_OCC_SRAM,
				  resp, resp_len, &parsed_len);
	if (rc > 0) {
		dev_err(occ->dev, "SRAM read returned failure status: %08x\n",
			rc);
		occ_save_ffdc(occ, resp, parsed_len, resp_len);
		return -ECOMM;
	} else if (rc) {
		return rc;
	}

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

	return rc;
}

static int occ_putsram(struct occ *occ, const void *data, ssize_t len,
		       u8 seq_no, u16 checksum)
{
	u32 data_len = ((len + 7) / 8) * 8;	/* must be multiples of 8 B */
	size_t cmd_len, parsed_len, resp_data_len;
	size_t resp_len = OCC_MAX_RESP_WORDS;
	__be32 *buf = occ->buffer;
	u8 *byte_buf;
	int idx = 0, rc;

	cmd_len = (occ->version == occ_p10) ? 6 : 5;
	cmd_len += data_len >> 2;

	/*
	 * 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);

	switch (occ->version) {
	default:
	case occ_p9:
		buf[2] = cpu_to_be32(1);	/* Normal mode */
		buf[3] = cpu_to_be32(OCC_P9_SRAM_CMD_ADDR);
		break;
	case occ_p10:
		idx = 1;
		buf[2] = cpu_to_be32(OCC_P10_SRAM_MODE);
		buf[3] = 0;
		buf[4] = cpu_to_be32(OCC_P10_SRAM_CMD_ADDR);
		break;
	}

	buf[4 + idx] = cpu_to_be32(data_len);
	memcpy(&buf[5 + idx], data, len);

	byte_buf = (u8 *)&buf[5 + idx];
	/*
	 * Overwrite the first byte with our sequence number and the last two
	 * bytes with the checksum.
	 */
	byte_buf[0] = seq_no;
	byte_buf[len - 2] = checksum >> 8;
	byte_buf[len - 1] = checksum & 0xff;

	rc = sbefifo_submit(occ->sbefifo, buf, cmd_len, buf, &resp_len);
	if (rc)
		return rc;

	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
				  buf, resp_len, &parsed_len);
	if (rc > 0) {
		dev_err(occ->dev, "SRAM write returned failure status: %08x\n",
			rc);
		occ_save_ffdc(occ, buf, parsed_len, resp_len);
		return -ECOMM;
	} else if (rc) {
		return rc;
	}

	if (parsed_len != 1) {
		dev_err(occ->dev, "SRAM write response length invalid: %zd\n",
			parsed_len);
		rc = -EBADMSG;
	} else {
		resp_data_len = be32_to_cpu(buf[0]);
		if (resp_data_len != data_len) {
			dev_err(occ->dev,
				"SRAM write expected %d bytes got %zd\n",
				data_len, resp_data_len);
			rc = -EBADMSG;
		}
	}

	return rc;
}

static int occ_trigger_attn(struct occ *occ)
{
	__be32 *buf = occ->buffer;
	size_t cmd_len, parsed_len, resp_data_len;
	size_t resp_len = OCC_MAX_RESP_WORDS;
	int idx = 0, rc;

	switch (occ->version) {
	default:
	case occ_p9:
		cmd_len = 7;
		buf[2] = cpu_to_be32(3); /* Circular mode */
		buf[3] = 0;
		break;
	case occ_p10:
		idx = 1;
		cmd_len = 8;
		buf[2] = cpu_to_be32(0xd0); /* Circular mode, OCB Channel 1 */
		buf[3] = 0;
		buf[4] = 0;
		break;
	}

	buf[0] = cpu_to_be32(cmd_len);		/* Chip-op length in words */
	buf[1] = cpu_to_be32(SBEFIFO_CMD_PUT_OCC_SRAM);
	buf[4 + idx] = cpu_to_be32(8);		/* Data length in bytes */
	buf[5 + idx] = cpu_to_be32(0x20010000);	/* Trigger OCC attention */
	buf[6 + idx] = 0;

	rc = sbefifo_submit(occ->sbefifo, buf, cmd_len, buf, &resp_len);
	if (rc)
		return rc;

	rc = sbefifo_parse_status(occ->sbefifo, SBEFIFO_CMD_PUT_OCC_SRAM,
				  buf, resp_len, &parsed_len);
	if (rc > 0) {
		dev_err(occ->dev, "SRAM attn returned failure status: %08x\n",
			rc);
		occ_save_ffdc(occ, buf, parsed_len, resp_len);
		return -ECOMM;
	} else if (rc) {
		return rc;
	}

	if (parsed_len != 1) {
		dev_err(occ->dev, "SRAM attn response length invalid: %zd\n",
			parsed_len);
		rc = -EBADMSG;
	} else {
		resp_data_len = be32_to_cpu(buf[0]);
		if (resp_data_len != 8) {
			dev_err(occ->dev,
				"SRAM attn expected 8 bytes got %zd\n",
				resp_data_len);
			rc = -EBADMSG;
		}
	}

	return rc;
}

static bool fsi_occ_response_not_ready(struct occ_response *resp, u8 seq_no,
				       u8 cmd_type)
{
	return resp->return_status == OCC_RESP_CMD_IN_PRG ||
		resp->return_status == OCC_RESP_CRIT_INIT ||
		resp->seq_no != seq_no || resp->cmd_type != cmd_type;
}

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;
	size_t user_resp_len = *resp_len;
	u8 seq_no;
	u8 cmd_type;
	u16 checksum = 0;
	u16 resp_data_length;
	const u8 *byte_request = (const u8 *)request;
	unsigned long end;
	int rc;
	size_t i;

	*resp_len = 0;

	if (!occ)
		return -ENODEV;

	if (user_resp_len < 7) {
		dev_dbg(dev, "Bad resplen %zd\n", user_resp_len);
		return -EINVAL;
	}

	cmd_type = byte_request[1];

	/* Checksum the request, ignoring first byte (sequence number). */
	for (i = 1; i < req_len - 2; ++i)
		checksum += byte_request[i];

	rc = mutex_lock_interruptible(&occ->occ_lock);
	if (rc)
		return rc;

	occ->client_buffer = response;
	occ->client_buffer_size = user_resp_len;
	occ->client_response_size = 0;

	if (!occ->buffer) {
		rc = -ENOENT;
		goto done;
	}

	/*
	 * Get a sequence number and update the counter. Avoid a sequence
	 * number of 0 which would pass the response check below even if the
	 * OCC response is uninitialized. Any sequence number the user is
	 * trying to send is overwritten since this function is the only common
	 * interface to the OCC and therefore the only place we can guarantee
	 * unique sequence numbers.
	 */
	seq_no = occ->sequence_number++;
	if (!occ->sequence_number)
		occ->sequence_number = 1;
	checksum += seq_no;

	rc = occ_putsram(occ, request, req_len, seq_no, checksum);
	if (rc)
		goto done;

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

	end = jiffies + timeout;
	while (true) {
		/* Read occ response header */
		rc = occ_getsram(occ, 0, resp, 8);
		if (rc)
			goto done;

		if (fsi_occ_response_not_ready(resp, seq_no, cmd_type)) {
			if (time_after(jiffies, end)) {
				dev_err(occ->dev,
					"resp timeout status=%02x seq=%d cmd=%d, our seq=%d cmd=%d\n",
					resp->return_status, resp->seq_no,
					resp->cmd_type, seq_no, cmd_type);
				rc = -ETIMEDOUT;
				goto done;
			}

			set_current_state(TASK_UNINTERRUPTIBLE);
			schedule_timeout(wait_time);
		} else {
			/* 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) > user_resp_len) {
				rc = -EMSGSIZE;
				goto done;
			}

			/*
			 * Get the entire response including the header again,
			 * in case it changed
			 */
			if (resp_data_length > 1) {
				rc = occ_getsram(occ, 0, resp,
						 resp_data_length + 7);
				if (rc)
					goto done;

				if (!fsi_occ_response_not_ready(resp, seq_no,
								cmd_type))
					break;
			} else {
				break;
			}
		}
	}

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

	occ->client_response_size = resp_data_length + 7;
	rc = occ_verify_checksum(occ, resp, resp_data_length);

 done:
	*resp_len = occ->client_response_size;
	mutex_unlock(&occ->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 int occ_probe(struct platform_device *pdev)
{
	int rc;
	u32 reg;
	struct occ *occ;
	struct platform_device *hwmon_dev;
	struct device *dev = &pdev->dev;
	struct platform_device_info hwmon_dev_info = {
		.parent = dev,
		.name = "occ-hwmon",
	};

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

	/* SBE words are always four bytes */
	occ->buffer = kvmalloc(OCC_MAX_RESP_WORDS * 4, GFP_KERNEL);
	if (!occ->buffer)
		return -ENOMEM;

	occ->version = (uintptr_t)of_device_get_match_data(dev);
	occ->dev = dev;
	occ->sbefifo = dev->parent;
	/*
	 * Quickly derive a pseudo-random number from jiffies so that
	 * re-probing the driver doesn't accidentally overlap sequence numbers.
	 */
	occ->sequence_number = (u8)((jiffies % 0xff) + 1);
	mutex_init(&occ->occ_lock);

	if (dev->of_node) {
		rc = of_property_read_u32(dev->of_node, "reg", &reg);
		if (!rc) {
			/* make sure we don't have a duplicate from dts */
			occ->idx = ida_simple_get(&occ_ida, reg, reg + 1,
						  GFP_KERNEL);
			if (occ->idx < 0)
				occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX,
							  GFP_KERNEL);
		} else {
			occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX,
						  GFP_KERNEL);
		}
	} else {
		occ->idx = ida_simple_get(&occ_ida, 1, INT_MAX, GFP_KERNEL);
	}

	platform_set_drvdata(pdev, occ);

	snprintf(occ->name, sizeof(occ->name), "occ%d", occ->idx);
	occ->mdev.fops = &occ_fops;
	occ->mdev.minor = MISC_DYNAMIC_MINOR;
	occ->mdev.name = occ->name;
	occ->mdev.parent = dev;

	rc = misc_register(&occ->mdev);
	if (rc) {
		dev_err(dev, "failed to register miscdevice: %d\n", rc);
		ida_simple_remove(&occ_ida, occ->idx);
		kvfree(occ->buffer);
		return rc;
	}

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

	return 0;
}

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

	misc_deregister(&occ->mdev);

	mutex_lock(&occ->occ_lock);
	kvfree(occ->buffer);
	occ->buffer = NULL;
	mutex_unlock(&occ->occ_lock);

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

	ida_simple_remove(&occ_ida, occ->idx);

	return 0;
}

static const struct of_device_id occ_match[] = {
	{
		.compatible = "ibm,p9-occ",
		.data = (void *)occ_p9
	},
	{
		.compatible = "ibm,p10-occ",
		.data = (void *)occ_p10
	},
	{ },
};
MODULE_DEVICE_TABLE(of, occ_match);

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);

	ida_destroy(&occ_ida);
}

module_init(occ_init);
module_exit(occ_exit);

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