/*
 * drivers/i2c/busses/i2c-s6000.c
 *
 * Description: Driver for S6000 Family I2C Interface
 * Copyright (c) 2008 emlix GmbH
 * Author:	Oskar Schirmer <oskar@scara.com>
 *
 * Partially based on i2c-bfin-twi.c driver by <sonic.zhang@analog.com>
 * Copyright (c) 2005-2007 Analog Devices, Inc.
 *
 * 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.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/i2c/s6000.h>
#include <linux/timer.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/io.h>

#include "i2c-s6000.h"

#define DRV_NAME "i2c-s6000"

#define POLL_TIMEOUT	(2 * HZ)

struct s6i2c_if {
	u8 __iomem		*reg; /* memory mapped registers */
	int			irq;
	spinlock_t		lock;
	struct i2c_msg		*msgs; /* messages currently handled */
	int			msgs_num; /* nb of msgs to do */
	int			msgs_push; /* nb of msgs read/written */
	int			msgs_done; /* nb of msgs finally handled */
	unsigned		push; /* nb of bytes read/written in msg */
	unsigned		done; /* nb of bytes finally handled */
	int			timeout_count; /* timeout retries left */
	struct timer_list	timeout_timer;
	struct i2c_adapter	adap;
	struct completion	complete;
	struct clk		*clk;
	struct resource		*res;
};

static inline u16 i2c_rd16(struct s6i2c_if *iface, unsigned n)
{
	return readw(iface->reg + (n));
}

static inline void i2c_wr16(struct s6i2c_if *iface, unsigned n, u16 v)
{
	writew(v, iface->reg + (n));
}

static inline u32 i2c_rd32(struct s6i2c_if *iface, unsigned n)
{
	return readl(iface->reg + (n));
}

static inline void i2c_wr32(struct s6i2c_if *iface, unsigned n, u32 v)
{
	writel(v, iface->reg + (n));
}

static struct s6i2c_if s6i2c_if;

static void s6i2c_handle_interrupt(struct s6i2c_if *iface)
{
	if (i2c_rd16(iface, S6_I2C_INTRSTAT) & (1 << S6_I2C_INTR_TXABRT)) {
		i2c_rd16(iface, S6_I2C_CLRTXABRT);
		i2c_wr16(iface, S6_I2C_INTRMASK, 0);
		complete(&iface->complete);
		return;
	}
	if (iface->msgs_done >= iface->msgs_num) {
		dev_err(&iface->adap.dev, "s6i2c: spurious I2C irq: %04x\n",
			i2c_rd16(iface, S6_I2C_INTRSTAT));
		i2c_wr16(iface, S6_I2C_INTRMASK, 0);
		return;
	}
	while ((iface->msgs_push < iface->msgs_num)
	    && (i2c_rd16(iface, S6_I2C_STATUS) & (1 << S6_I2C_STATUS_TFNF))) {
		struct i2c_msg *m = &iface->msgs[iface->msgs_push];
		if (!(m->flags & I2C_M_RD))
			i2c_wr16(iface, S6_I2C_DATACMD, m->buf[iface->push]);
		else
			i2c_wr16(iface, S6_I2C_DATACMD,
				 1 << S6_I2C_DATACMD_READ);
		if (++iface->push >= m->len) {
			iface->push = 0;
			iface->msgs_push += 1;
		}
	}
	do {
		struct i2c_msg *m = &iface->msgs[iface->msgs_done];
		if (!(m->flags & I2C_M_RD)) {
			if (iface->msgs_done < iface->msgs_push)
				iface->msgs_done += 1;
			else
				break;
		} else if (i2c_rd16(iface, S6_I2C_STATUS)
				& (1 << S6_I2C_STATUS_RFNE)) {
			m->buf[iface->done] = i2c_rd16(iface, S6_I2C_DATACMD);
			if (++iface->done >= m->len) {
				iface->done = 0;
				iface->msgs_done += 1;
			}
		} else{
			break;
		}
	} while (iface->msgs_done < iface->msgs_num);
	if (iface->msgs_done >= iface->msgs_num) {
		i2c_wr16(iface, S6_I2C_INTRMASK, 1 << S6_I2C_INTR_TXABRT);
		complete(&iface->complete);
	} else if (iface->msgs_push >= iface->msgs_num) {
		i2c_wr16(iface, S6_I2C_INTRMASK, (1 << S6_I2C_INTR_TXABRT) |
						 (1 << S6_I2C_INTR_RXFULL));
	} else {
		i2c_wr16(iface, S6_I2C_INTRMASK, (1 << S6_I2C_INTR_TXABRT) |
						 (1 << S6_I2C_INTR_TXEMPTY) |
						 (1 << S6_I2C_INTR_RXFULL));
	}
}

static irqreturn_t s6i2c_interrupt_entry(int irq, void *dev_id)
{
	struct s6i2c_if *iface = dev_id;
	if (!(i2c_rd16(iface, S6_I2C_STATUS) & ((1 << S6_I2C_INTR_RXUNDER)
					      | (1 << S6_I2C_INTR_RXOVER)
					      | (1 << S6_I2C_INTR_RXFULL)
					      | (1 << S6_I2C_INTR_TXOVER)
					      | (1 << S6_I2C_INTR_TXEMPTY)
					      | (1 << S6_I2C_INTR_RDREQ)
					      | (1 << S6_I2C_INTR_TXABRT)
					      | (1 << S6_I2C_INTR_RXDONE)
					      | (1 << S6_I2C_INTR_ACTIVITY)
					      | (1 << S6_I2C_INTR_STOPDET)
					      | (1 << S6_I2C_INTR_STARTDET)
					      | (1 << S6_I2C_INTR_GENCALL))))
		return IRQ_NONE;

	spin_lock(&iface->lock);
	del_timer(&iface->timeout_timer);
	s6i2c_handle_interrupt(iface);
	spin_unlock(&iface->lock);
	return IRQ_HANDLED;
}

static void s6i2c_timeout(unsigned long data)
{
	struct s6i2c_if *iface = (struct s6i2c_if *)data;
	unsigned long flags;

	spin_lock_irqsave(&iface->lock, flags);
	s6i2c_handle_interrupt(iface);
	if (--iface->timeout_count > 0) {
		iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
		add_timer(&iface->timeout_timer);
	} else {
		complete(&iface->complete);
		i2c_wr16(iface, S6_I2C_INTRMASK, 0);
	}
	spin_unlock_irqrestore(&iface->lock, flags);
}

static int s6i2c_master_xfer(struct i2c_adapter *adap,
				struct i2c_msg *msgs, int num)
{
	struct s6i2c_if *iface = adap->algo_data;
	int i;
	if (num == 0)
		return 0;
	if (i2c_rd16(iface, S6_I2C_STATUS) & (1 << S6_I2C_STATUS_ACTIVITY))
		yield();
	i2c_wr16(iface, S6_I2C_INTRMASK, 0);
	i2c_rd16(iface, S6_I2C_CLRINTR);
	for (i = 0; i < num; i++) {
		if (msgs[i].flags & I2C_M_TEN) {
			dev_err(&adap->dev,
				"s6i2c: 10 bits addr not supported\n");
			return -EINVAL;
		}
		if (msgs[i].len == 0) {
			dev_err(&adap->dev,
				"s6i2c: zero length message not supported\n");
			return -EINVAL;
		}
		if (msgs[i].addr != msgs[0].addr) {
			dev_err(&adap->dev,
				"s6i2c: multiple xfer cannot change target\n");
			return -EINVAL;
		}
	}

	iface->msgs = msgs;
	iface->msgs_num = num;
	iface->msgs_push = 0;
	iface->msgs_done = 0;
	iface->push = 0;
	iface->done = 0;
	iface->timeout_count = 10;
	i2c_wr16(iface, S6_I2C_TAR, msgs[0].addr);
	i2c_wr16(iface, S6_I2C_ENABLE, 1);
	i2c_wr16(iface, S6_I2C_INTRMASK, (1 << S6_I2C_INTR_TXEMPTY) |
					 (1 << S6_I2C_INTR_TXABRT));

	iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
	add_timer(&iface->timeout_timer);
	wait_for_completion(&iface->complete);
	del_timer_sync(&iface->timeout_timer);
	while (i2c_rd32(iface, S6_I2C_TXFLR) > 0)
		schedule();
	while (i2c_rd16(iface, S6_I2C_STATUS) & (1 << S6_I2C_STATUS_ACTIVITY))
		schedule();

	i2c_wr16(iface, S6_I2C_INTRMASK, 0);
	i2c_wr16(iface, S6_I2C_ENABLE, 0);
	return iface->msgs_done;
}

static u32 s6i2c_functionality(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static struct i2c_algorithm s6i2c_algorithm = {
	.master_xfer   = s6i2c_master_xfer,
	.functionality = s6i2c_functionality,
};

static u16 nanoseconds_on_clk(struct s6i2c_if *iface, u32 ns)
{
	u32 dividend = ((clk_get_rate(iface->clk) / 1000) * ns) / 1000000;
	if (dividend > 0xffff)
		return 0xffff;
	return dividend;
}

static int s6i2c_probe(struct platform_device *dev)
{
	struct s6i2c_if *iface = &s6i2c_if;
	struct i2c_adapter *p_adap;
	const char *clock;
	int bus_num, rc;
	spin_lock_init(&iface->lock);
	init_completion(&iface->complete);
	iface->irq = platform_get_irq(dev, 0);
	if (iface->irq < 0) {
		rc = iface->irq;
		goto err_out;
	}
	iface->res = platform_get_resource(dev, IORESOURCE_MEM, 0);
	if (!iface->res) {
		rc = -ENXIO;
		goto err_out;
	}
	iface->res = request_mem_region(iface->res->start,
					resource_size(iface->res),
					dev->dev.bus_id);
	if (!iface->res) {
		rc = -EBUSY;
		goto err_out;
	}
	iface->reg = ioremap_nocache(iface->res->start,
				     resource_size(iface->res));
	if (!iface->reg) {
		rc = -ENOMEM;
		goto err_reg;
	}

	clock = 0;
	bus_num = -1;
	if (dev->dev.platform_data) {
		struct s6_i2c_platform_data *pdata = dev->dev.platform_data;
		bus_num = pdata->bus_num;
		clock = pdata->clock;
	}
	iface->clk = clk_get(&dev->dev, clock);
	if (IS_ERR(iface->clk)) {
		rc = PTR_ERR(iface->clk);
		goto err_map;
	}
	rc = clk_enable(iface->clk);
	if (rc < 0)
		goto err_clk_put;
	init_timer(&iface->timeout_timer);
	iface->timeout_timer.function = s6i2c_timeout;
	iface->timeout_timer.data = (unsigned long)iface;

	p_adap = &iface->adap;
	strlcpy(p_adap->name, dev->name, sizeof(p_adap->name));
	p_adap->algo = &s6i2c_algorithm;
	p_adap->algo_data = iface;
	p_adap->nr = bus_num;
	p_adap->class = 0;
	p_adap->dev.parent = &dev->dev;
	i2c_wr16(iface, S6_I2C_INTRMASK, 0);
	rc = request_irq(iface->irq, s6i2c_interrupt_entry,
			 IRQF_SHARED, dev->name, iface);
	if (rc) {
		dev_err(&p_adap->dev, "s6i2c: can't get IRQ %d\n", iface->irq);
		goto err_clk_dis;
	}

	i2c_wr16(iface, S6_I2C_ENABLE, 0);
	udelay(1);
	i2c_wr32(iface, S6_I2C_SRESET, 1 << S6_I2C_SRESET_IC_SRST);
	i2c_wr16(iface, S6_I2C_CLRTXABRT, 1);
	i2c_wr16(iface, S6_I2C_CON,
			(1 << S6_I2C_CON_MASTER) |
			(S6_I2C_CON_SPEED_NORMAL << S6_I2C_CON_SPEED) |
			(0 << S6_I2C_CON_10BITSLAVE) |
			(0 << S6_I2C_CON_10BITMASTER) |
			(1 << S6_I2C_CON_RESTARTENA) |
			(1 << S6_I2C_CON_SLAVEDISABLE));
	i2c_wr16(iface, S6_I2C_SSHCNT, nanoseconds_on_clk(iface, 4000));
	i2c_wr16(iface, S6_I2C_SSLCNT, nanoseconds_on_clk(iface, 4700));
	i2c_wr16(iface, S6_I2C_FSHCNT, nanoseconds_on_clk(iface, 600));
	i2c_wr16(iface, S6_I2C_FSLCNT, nanoseconds_on_clk(iface, 1300));
	i2c_wr16(iface, S6_I2C_RXTL, 0);
	i2c_wr16(iface, S6_I2C_TXTL, 0);

	platform_set_drvdata(dev, iface);
	rc = i2c_add_numbered_adapter(p_adap);
	if (rc)
		goto err_irq_free;
	return 0;

err_irq_free:
	free_irq(iface->irq, iface);
err_clk_dis:
	clk_disable(iface->clk);
err_clk_put:
	clk_put(iface->clk);
err_map:
	iounmap(iface->reg);
err_reg:
	release_mem_region(iface->res->start,
			   resource_size(iface->res));
err_out:
	return rc;
}

static int s6i2c_remove(struct platform_device *pdev)
{
	struct s6i2c_if *iface = platform_get_drvdata(pdev);
	i2c_wr16(iface, S6_I2C_ENABLE, 0);
	i2c_del_adapter(&iface->adap);
	free_irq(iface->irq, iface);
	clk_disable(iface->clk);
	clk_put(iface->clk);
	iounmap(iface->reg);
	release_mem_region(iface->res->start,
			   resource_size(iface->res));
	return 0;
}

static struct platform_driver s6i2c_driver = {
	.probe		= s6i2c_probe,
	.remove		= s6i2c_remove,
	.driver		= {
		.name	= DRV_NAME,
		.owner	= THIS_MODULE,
	},
};

static int __init s6i2c_init(void)
{
	pr_info("I2C: S6000 I2C driver\n");
	return platform_driver_register(&s6i2c_driver);
}

static void __exit s6i2c_exit(void)
{
	platform_driver_unregister(&s6i2c_driver);
}

MODULE_DESCRIPTION("I2C-Bus adapter routines for S6000 I2C");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRV_NAME);

subsys_initcall(s6i2c_init);
module_exit(s6i2c_exit);