/*
 * FSI core 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
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/crc4.h>
#include <linux/device.h>
#include <linux/fsi.h>
#include <linux/idr.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "fsi-master.h"

#define FSI_SLAVE_BASE			0x800

/*
 * FSI slave engine control register offsets
 */
#define FSI_SMODE			0x0	/* R/W: Mode register */

/*
 * SMODE fields
 */
#define FSI_SMODE_WSC		0x80000000	/* Warm start done */
#define FSI_SMODE_ECRC		0x20000000	/* Hw CRC check */
#define FSI_SMODE_SID_SHIFT	24		/* ID shift */
#define FSI_SMODE_SID_MASK	3		/* ID Mask */
#define FSI_SMODE_ED_SHIFT	20		/* Echo delay shift */
#define FSI_SMODE_ED_MASK	0xf		/* Echo delay mask */
#define FSI_SMODE_SD_SHIFT	16		/* Send delay shift */
#define FSI_SMODE_SD_MASK	0xf		/* Send delay mask */
#define FSI_SMODE_LBCRR_SHIFT	8		/* Clk ratio shift */
#define FSI_SMODE_LBCRR_MASK	0xf		/* Clk ratio mask */

#define FSI_SLAVE_SIZE_23b		0x800000

static DEFINE_IDA(master_ida);

struct fsi_slave {
	struct device		dev;
	struct fsi_master	*master;
	int			id;
	int			link;
	uint32_t		size;	/* size of slave address space */
};

#define to_fsi_slave(d) container_of(d, struct fsi_slave, dev)

static int fsi_master_read(struct fsi_master *master, int link,
		uint8_t slave_id, uint32_t addr, void *val, size_t size);
static int fsi_master_write(struct fsi_master *master, int link,
		uint8_t slave_id, uint32_t addr, const void *val, size_t size);

/* FSI slave support */
static int fsi_slave_calc_addr(struct fsi_slave *slave, uint32_t *addrp,
		uint8_t *idp)
{
	uint32_t addr = *addrp;
	uint8_t id = *idp;

	if (addr > slave->size)
		return -EINVAL;

	/* For 23 bit addressing, we encode the extra two bits in the slave
	 * id (and the slave's actual ID needs to be 0).
	 */
	if (addr > 0x1fffff) {
		if (slave->id != 0)
			return -EINVAL;
		id = (addr >> 21) & 0x3;
		addr &= 0x1fffff;
	}

	*addrp = addr;
	*idp = id;
	return 0;
}

static int fsi_slave_read(struct fsi_slave *slave, uint32_t addr,
			void *val, size_t size)
{
	uint8_t id = slave->id;
	int rc;

	rc = fsi_slave_calc_addr(slave, &addr, &id);
	if (rc)
		return rc;

	return fsi_master_read(slave->master, slave->link, id,
			addr, val, size);
}

static int fsi_slave_write(struct fsi_slave *slave, uint32_t addr,
			const void *val, size_t size)
{
	uint8_t id = slave->id;
	int rc;

	rc = fsi_slave_calc_addr(slave, &addr, &id);
	if (rc)
		return rc;

	return fsi_master_write(slave->master, slave->link, id,
			addr, val, size);
}

/* Encode slave local bus echo delay */
static inline uint32_t fsi_smode_echodly(int x)
{
	return (x & FSI_SMODE_ED_MASK) << FSI_SMODE_ED_SHIFT;
}

/* Encode slave local bus send delay */
static inline uint32_t fsi_smode_senddly(int x)
{
	return (x & FSI_SMODE_SD_MASK) << FSI_SMODE_SD_SHIFT;
}

/* Encode slave local bus clock rate ratio */
static inline uint32_t fsi_smode_lbcrr(int x)
{
	return (x & FSI_SMODE_LBCRR_MASK) << FSI_SMODE_LBCRR_SHIFT;
}

/* Encode slave ID */
static inline uint32_t fsi_smode_sid(int x)
{
	return (x & FSI_SMODE_SID_MASK) << FSI_SMODE_SID_SHIFT;
}

static const uint32_t fsi_slave_smode(int id)
{
	return FSI_SMODE_WSC | FSI_SMODE_ECRC
		| fsi_smode_sid(id)
		| fsi_smode_echodly(0xf) | fsi_smode_senddly(0xf)
		| fsi_smode_lbcrr(0x8);
}

static int fsi_slave_set_smode(struct fsi_master *master, int link, int id)
{
	uint32_t smode;

	/* set our smode register with the slave ID field to 0; this enables
	 * extended slave addressing
	 */
	smode = fsi_slave_smode(id);
	smode = cpu_to_be32(smode);

	return fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SMODE,
			&smode, sizeof(smode));
}

static void fsi_slave_release(struct device *dev)
{
	struct fsi_slave *slave = to_fsi_slave(dev);

	kfree(slave);
}

static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
{
	struct fsi_slave *slave;
	uint32_t chip_id;
	uint8_t crc;
	int rc;

	/* Currently, we only support single slaves on a link, and use the
	 * full 23-bit address range
	 */
	if (id != 0)
		return -EINVAL;

	rc = fsi_master_read(master, link, id, 0, &chip_id, sizeof(chip_id));
	if (rc) {
		dev_dbg(&master->dev, "can't read slave %02x:%02x %d\n",
				link, id, rc);
		return -ENODEV;
	}
	chip_id = be32_to_cpu(chip_id);

	crc = crc4(0, chip_id, 32);
	if (crc) {
		dev_warn(&master->dev, "slave %02x:%02x invalid chip id CRC!\n",
				link, id);
		return -EIO;
	}

	dev_info(&master->dev, "fsi: found chip %08x at %02x:%02x:%02x\n",
			chip_id, master->idx, link, id);

	rc = fsi_slave_set_smode(master, link, id);
	if (rc) {
		dev_warn(&master->dev,
				"can't set smode on slave:%02x:%02x %d\n",
				link, id, rc);
		return -ENODEV;
	}

	/* We can communicate with a slave; create the slave device and
	 * register.
	 */
	slave = kzalloc(sizeof(*slave), GFP_KERNEL);
	if (!slave)
		return -ENOMEM;

	slave->master = master;
	slave->dev.parent = &master->dev;
	slave->dev.release = fsi_slave_release;
	slave->link = link;
	slave->id = id;
	slave->size = FSI_SLAVE_SIZE_23b;

	dev_set_name(&slave->dev, "slave@%02x:%02x", link, id);
	rc = device_register(&slave->dev);
	if (rc < 0) {
		dev_warn(&master->dev, "failed to create slave device: %d\n",
				rc);
		put_device(&slave->dev);
		return rc;
	}

	/* todo: perform engine scan */

	return rc;
}

/* FSI master support */
static int fsi_check_access(uint32_t addr, size_t size)
{
	if (size != 1 && size != 2 && size != 4)
		return -EINVAL;

	if ((addr & 0x3) != (size & 0x3))
		return -EINVAL;

	return 0;
}

static int fsi_master_read(struct fsi_master *master, int link,
		uint8_t slave_id, uint32_t addr, void *val, size_t size)
{
	int rc;

	rc = fsi_check_access(addr, size);
	if (rc)
		return rc;

	return master->read(master, link, slave_id, addr, val, size);
}

static int fsi_master_write(struct fsi_master *master, int link,
		uint8_t slave_id, uint32_t addr, const void *val, size_t size)
{
	int rc;

	rc = fsi_check_access(addr, size);
	if (rc)
		return rc;

	return master->write(master, link, slave_id, addr, val, size);
}

static int fsi_master_link_enable(struct fsi_master *master, int link)
{
	if (master->link_enable)
		return master->link_enable(master, link);

	return 0;
}

/*
 * Issue a break command on this link
 */
static int fsi_master_break(struct fsi_master *master, int link)
{
	if (master->send_break)
		return master->send_break(master, link);

	return 0;
}

static int fsi_master_scan(struct fsi_master *master)
{
	int link, rc;

	for (link = 0; link < master->n_links; link++) {
		rc = fsi_master_link_enable(master, link);
		if (rc) {
			dev_dbg(&master->dev,
				"enable link %d failed: %d\n", link, rc);
			continue;
		}
		rc = fsi_master_break(master, link);
		if (rc) {
			dev_dbg(&master->dev,
				"break to link %d failed: %d\n", link, rc);
			continue;
		}

		fsi_slave_init(master, link, 0);
	}

	return 0;
}

int fsi_master_register(struct fsi_master *master)
{
	int rc;

	if (!master)
		return -EINVAL;

	master->idx = ida_simple_get(&master_ida, 0, INT_MAX, GFP_KERNEL);
	dev_set_name(&master->dev, "fsi%d", master->idx);

	rc = device_register(&master->dev);
	if (rc) {
		ida_simple_remove(&master_ida, master->idx);
		return rc;
	}

	fsi_master_scan(master);
	return 0;
}
EXPORT_SYMBOL_GPL(fsi_master_register);

void fsi_master_unregister(struct fsi_master *master)
{
	if (master->idx >= 0) {
		ida_simple_remove(&master_ida, master->idx);
		master->idx = -1;
	}

	device_unregister(&master->dev);
}
EXPORT_SYMBOL_GPL(fsi_master_unregister);

/* FSI core & Linux bus type definitions */

static int fsi_bus_match(struct device *dev, struct device_driver *drv)
{
	struct fsi_device *fsi_dev = to_fsi_dev(dev);
	struct fsi_driver *fsi_drv = to_fsi_drv(drv);
	const struct fsi_device_id *id;

	if (!fsi_drv->id_table)
		return 0;

	for (id = fsi_drv->id_table; id->engine_type; id++) {
		if (id->engine_type != fsi_dev->engine_type)
			continue;
		if (id->version == FSI_VERSION_ANY ||
				id->version == fsi_dev->version)
			return 1;
	}

	return 0;
}

struct bus_type fsi_bus_type = {
	.name		= "fsi",
	.match		= fsi_bus_match,
};
EXPORT_SYMBOL_GPL(fsi_bus_type);

static int fsi_init(void)
{
	return bus_register(&fsi_bus_type);
}

static void fsi_exit(void)
{
	bus_unregister(&fsi_bus_type);
}

module_init(fsi_init);
module_exit(fsi_exit);