// SPDX-License-Identifier: GPL-2.0
/*
 * I2C driver for stand-alone PCF8584 style adapters on Zorro cards
 *
 * Original ICY documentation can be found on Aminet:
 * https://aminet.net/package/docs/hard/icy
 *
 * There has been a modern community re-print of this design in 2019:
 * https://www.a1k.org/forum/index.php?threads/70106/
 *
 * The card is basically a Philips PCF8584 connected straight to the
 * beginning of the AutoConfig'd address space (register S1 on base+2),
 * with /INT on /INT2 on the Zorro bus.
 *
 * Copyright (c) 2019 Max Staudt <max@enpas.org>
 *
 * This started as a fork of i2c-elektor.c and has evolved since.
 * Thanks go to its authors for providing a base to grow on.
 *
 *
 * IRQ support is currently not implemented.
 *
 * As it turns out, i2c-algo-pcf is really written with i2c-elektor's
 * edge-triggered ISA interrupts in mind, while the Amiga's Zorro bus has
 * level-triggered interrupts. This means that once an interrupt occurs, we
 * have to tell the PCF8584 to shut up immediately, or it will keep the
 * interrupt line busy and cause an IRQ storm.

 * However, because of the PCF8584's host-side protocol, there is no good
 * way to just quieten it without side effects. Rather, we have to perform
 * the next read/write operation straight away, which will reset the /INT
 * pin. This entails re-designing the core of i2c-algo-pcf in the future.
 * For now, we never request an IRQ from the PCF8584, and poll it instead.
 */

#include <linux/delay.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/i2c-algo-pcf.h>

#include <asm/amigaints.h>
#include <linux/zorro.h>

#include "../algos/i2c-algo-pcf.h"

struct icy_i2c {
	struct i2c_adapter adapter;

	void __iomem *reg_s0;
	void __iomem *reg_s1;
};

/*
 * Functions called by i2c-algo-pcf
 */
static void icy_pcf_setpcf(void *data, int ctl, int val)
{
	struct icy_i2c *i2c = (struct icy_i2c *)data;

	u8 __iomem *address = ctl ? i2c->reg_s1 : i2c->reg_s0;

	z_writeb(val, address);
}

static int icy_pcf_getpcf(void *data, int ctl)
{
	struct icy_i2c *i2c = (struct icy_i2c *)data;

	u8 __iomem *address = ctl ? i2c->reg_s1 : i2c->reg_s0;

	return z_readb(address);
}

static int icy_pcf_getown(void *data)
{
	return 0x55;
}

static int icy_pcf_getclock(void *data)
{
	return 0x1c;
}

static void icy_pcf_waitforpin(void *data)
{
	usleep_range(50, 150);
}

/*
 * Main i2c-icy part
 */
static int icy_probe(struct zorro_dev *z,
		     const struct zorro_device_id *ent)
{
	struct icy_i2c *i2c;
	struct i2c_algo_pcf_data *algo_data;

	i2c = devm_kzalloc(&z->dev, sizeof(*i2c), GFP_KERNEL);
	if (!i2c)
		return -ENOMEM;

	algo_data = devm_kzalloc(&z->dev, sizeof(*algo_data), GFP_KERNEL);
	if (!algo_data)
		return -ENOMEM;

	dev_set_drvdata(&z->dev, i2c);
	i2c->adapter.dev.parent = &z->dev;
	i2c->adapter.owner = THIS_MODULE;
	/* i2c->adapter.algo assigned by i2c_pcf_add_bus() */
	i2c->adapter.algo_data = algo_data;
	strlcpy(i2c->adapter.name, "ICY I2C Zorro adapter",
		sizeof(i2c->adapter.name));

	if (!devm_request_mem_region(&z->dev,
				     z->resource.start,
				     4, i2c->adapter.name))
		return -ENXIO;

	/* Driver private data */
	i2c->reg_s0 = ZTWO_VADDR(z->resource.start);
	i2c->reg_s1 = ZTWO_VADDR(z->resource.start + 2);

	algo_data->data = i2c;
	algo_data->setpcf     = icy_pcf_setpcf;
	algo_data->getpcf     = icy_pcf_getpcf;
	algo_data->getown     = icy_pcf_getown;
	algo_data->getclock   = icy_pcf_getclock;
	algo_data->waitforpin = icy_pcf_waitforpin;

	if (i2c_pcf_add_bus(&i2c->adapter)) {
		dev_err(&z->dev, "i2c_pcf_add_bus() failed\n");
		return -ENXIO;
	}

	dev_info(&z->dev, "ICY I2C controller at %pa, IRQ not implemented\n",
		 &z->resource.start);

	return 0;
}

static void icy_remove(struct zorro_dev *z)
{
	struct icy_i2c *i2c = dev_get_drvdata(&z->dev);

	i2c_del_adapter(&i2c->adapter);
}

static const struct zorro_device_id icy_zorro_tbl[] = {
	{ ZORRO_ID(VMC, 15, 0), },
	{ 0 }
};

MODULE_DEVICE_TABLE(zorro, icy_zorro_tbl);

static struct zorro_driver icy_driver = {
	.name           = "i2c-icy",
	.id_table       = icy_zorro_tbl,
	.probe          = icy_probe,
	.remove         = icy_remove,
};

module_driver(icy_driver,
	      zorro_register_driver,
	      zorro_unregister_driver);

MODULE_AUTHOR("Max Staudt <max@enpas.org>");
MODULE_DESCRIPTION("I2C bus via PCF8584 on ICY Zorro card");
MODULE_LICENSE("GPL v2");