/*
 * AMD CS5535/CS5536 GPIO driver.
 * Allows a user space process to play with the GPIO pins.
 *
 * Copyright (c) 2005 Ben Gardner <bgardner@wabtec.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the smems of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 */

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <linux/ioport.h>
#include <linux/pci.h>
#include <asm/uaccess.h>
#include <asm/io.h>


#define NAME			"cs5535_gpio"

MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
MODULE_DESCRIPTION("AMD CS5535/CS5536 GPIO Pin Driver");
MODULE_LICENSE("GPL");

static int major;
module_param(major, int, 0);
MODULE_PARM_DESC(major, "Major device number");

static ulong mask;
module_param(mask, ulong, 0);
MODULE_PARM_DESC(mask, "GPIO channel mask");

#define MSR_LBAR_GPIO		0x5140000C

static u32 gpio_base;

static struct pci_device_id divil_pci[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_NS,  PCI_DEVICE_ID_NS_CS5535_ISA) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CS5536_ISA) },
	{ } /* NULL entry */
};

static struct cdev cs5535_gpio_cdev;

/* reserve 32 entries even though some aren't usable */
#define CS5535_GPIO_COUNT	32

/* IO block size */
#define CS5535_GPIO_SIZE	256

struct gpio_regmap {
	u32	rd_offset;
	u32	wr_offset;
	char	on;
	char	off;
};
static struct gpio_regmap rm[] =
{
	{ 0x30, 0x00, '1', '0' },	/* GPIOx_READ_BACK / GPIOx_OUT_VAL */
	{ 0x20, 0x20, 'I', 'i' },	/* GPIOx_IN_EN */
	{ 0x04, 0x04, 'O', 'o' },	/* GPIOx_OUT_EN */
	{ 0x08, 0x08, 't', 'T' },	/* GPIOx_OUT_OD_EN */
	{ 0x18, 0x18, 'P', 'p' },	/* GPIOx_OUT_PU_EN */
	{ 0x1c, 0x1c, 'D', 'd' },	/* GPIOx_OUT_PD_EN */
};


/**
 * Gets the register offset for the GPIO bank.
 * Low (0-15) starts at 0x00, high (16-31) starts at 0x80
 */
static inline u32 cs5535_lowhigh_base(int reg)
{
	return (reg & 0x10) << 3;
}

static ssize_t cs5535_gpio_write(struct file *file, const char __user *data,
				 size_t len, loff_t *ppos)
{
	u32	m = iminor(file->f_path.dentry->d_inode);
	int	i, j;
	u32	base = gpio_base + cs5535_lowhigh_base(m);
	u32	m0, m1;
	char	c;

	/**
	 * Creates the mask for atomic bit programming.
	 * The high 16 bits and the low 16 bits are used to set the mask.
	 * For example, GPIO 15 maps to 31,15: 0,1 => On; 1,0=> Off
	 */
	m1 = 1 << (m & 0x0F);
	m0 = m1 << 16;

	for (i = 0; i < len; ++i) {
		if (get_user(c, data+i))
			return -EFAULT;

		for (j = 0; j < ARRAY_SIZE(rm); j++) {
			if (c == rm[j].on) {
				outl(m1, base + rm[j].wr_offset);
				break;
			} else if (c == rm[j].off) {
				outl(m0, base + rm[j].wr_offset);
				break;
			}
		}
	}
	*ppos = 0;
	return len;
}

static ssize_t cs5535_gpio_read(struct file *file, char __user *buf,
				size_t len, loff_t *ppos)
{
	u32	m = iminor(file->f_path.dentry->d_inode);
	u32	base = gpio_base + cs5535_lowhigh_base(m);
	int	rd_bit = 1 << (m & 0x0f);
	int	i;
	char	ch;
	ssize_t	count = 0;

	if (*ppos >= ARRAY_SIZE(rm))
		return 0;

	for (i = *ppos; (i < (*ppos + len)) && (i < ARRAY_SIZE(rm)); i++) {
		ch = (inl(base + rm[i].rd_offset) & rd_bit) ?
		     rm[i].on : rm[i].off;

		if (put_user(ch, buf+count))
			return -EFAULT;

		count++;
	}

	/* add a line-feed if there is room */
	if ((i == ARRAY_SIZE(rm)) && (count < len)) {
		put_user('\n', buf + count);
		count++;
	}

	*ppos += count;
	return count;
}

static int cs5535_gpio_open(struct inode *inode, struct file *file)
{
	u32 m = iminor(inode);

	/* the mask says which pins are usable by this driver */
	if ((mask & (1 << m)) == 0)
		return -EINVAL;

	return nonseekable_open(inode, file);
}

static const struct file_operations cs5535_gpio_fops = {
	.owner	= THIS_MODULE,
	.write	= cs5535_gpio_write,
	.read	= cs5535_gpio_read,
	.open	= cs5535_gpio_open
};

static int __init cs5535_gpio_init(void)
{
	dev_t	dev_id;
	u32	low, hi;
	int	retval;

	if (pci_dev_present(divil_pci) == 0) {
		printk(KERN_WARNING NAME ": DIVIL not found\n");
		return -ENODEV;
	}

	/* Grab the GPIO I/O range */
	rdmsr(MSR_LBAR_GPIO, low, hi);

	/* Check the mask and whether GPIO is enabled (sanity check) */
	if (hi != 0x0000f001) {
		printk(KERN_WARNING NAME ": GPIO not enabled\n");
		return -ENODEV;
	}

	/* Mask off the IO base address */
	gpio_base = low & 0x0000ff00;

	/**
	 * Some GPIO pins
	 *  31-29,23 : reserved (always mask out)
	 *  28       : Power Button
	 *  26       : PME#
	 *  22-16    : LPC
	 *  14,15    : SMBus
	 *  9,8      : UART1
	 *  7        : PCI INTB
	 *  3,4      : UART2/DDC
	 *  2        : IDE_IRQ0
	 *  0        : PCI INTA
	 *
	 * If a mask was not specified, be conservative and only allow:
	 *  1,2,5,6,10-13,24,25,27
	 */
	if (mask != 0)
		mask &= 0x1f7fffff;
	else
		mask = 0x0b003c66;

	if (request_region(gpio_base, CS5535_GPIO_SIZE, NAME) == 0) {
		printk(KERN_ERR NAME ": can't allocate I/O for GPIO\n");
		return -ENODEV;
	}

	if (major) {
		dev_id = MKDEV(major, 0);
		retval = register_chrdev_region(dev_id, CS5535_GPIO_COUNT,
						NAME);
	} else {
		retval = alloc_chrdev_region(&dev_id, 0, CS5535_GPIO_COUNT,
					     NAME);
		major = MAJOR(dev_id);
	}

	if (retval) {
		release_region(gpio_base, CS5535_GPIO_SIZE);
		return -1;
	}

	printk(KERN_DEBUG NAME ": base=%#x mask=%#lx major=%d\n",
	       gpio_base, mask, major);

	cdev_init(&cs5535_gpio_cdev, &cs5535_gpio_fops);
	cdev_add(&cs5535_gpio_cdev, dev_id, CS5535_GPIO_COUNT);

	return 0;
}

static void __exit cs5535_gpio_cleanup(void)
{
	dev_t dev_id = MKDEV(major, 0);

	cdev_del(&cs5535_gpio_cdev);
	unregister_chrdev_region(dev_id, CS5535_GPIO_COUNT);
	release_region(gpio_base, CS5535_GPIO_SIZE);
}

module_init(cs5535_gpio_init);
module_exit(cs5535_gpio_cleanup);