xref: /openbmc/linux/drivers/i2c/busses/i2c-via.c (revision c942fddf)

// SPDX-License-Identifier: GPL-2.0-or-later
/*
    i2c Support for Via Technologies 82C586B South Bridge

    Copyright (c) 1998, 1999 Kyösti Mälkki <kmalkki@cc.hut.fi>

*/

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/ioport.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
#include <linux/io.h>

/* Power management registers */
#define PM_CFG_REVID	0x08	/* silicon revision code */
#define PM_CFG_IOBASE0	0x20
#define PM_CFG_IOBASE1	0x48

#define I2C_DIR		(pm_io_base+0x40)
#define I2C_OUT		(pm_io_base+0x42)
#define I2C_IN		(pm_io_base+0x44)
#define I2C_SCL		0x02	/* clock bit in DIR/OUT/IN register */
#define I2C_SDA		0x04

/* io-region reservation */
#define IOSPACE		0x06

static struct pci_driver vt586b_driver;
static u16 pm_io_base;

/*
   It does not appear from the datasheet that the GPIO pins are
   open drain. So a we set a low value by setting the direction to
   output and a high value by setting the direction to input and
   relying on the required I2C pullup. The data value is initialized
   to 0 in via_init() and never changed.
*/
static void bit_via_setscl(void *data, int state)
{
	outb(state ? inb(I2C_DIR) & ~I2C_SCL : inb(I2C_DIR) | I2C_SCL, I2C_DIR);
}

static void bit_via_setsda(void *data, int state)
{
	outb(state ? inb(I2C_DIR) & ~I2C_SDA : inb(I2C_DIR) | I2C_SDA, I2C_DIR);
}

static int bit_via_getscl(void *data)
{
	return (0 != (inb(I2C_IN) & I2C_SCL));
}

static int bit_via_getsda(void *data)
{
	return (0 != (inb(I2C_IN) & I2C_SDA));
}


static struct i2c_algo_bit_data bit_data = {
	.setsda		= bit_via_setsda,
	.setscl		= bit_via_setscl,
	.getsda		= bit_via_getsda,
	.getscl		= bit_via_getscl,
	.udelay		= 5,
	.timeout	= HZ
};

static struct i2c_adapter vt586b_adapter = {
	.owner		= THIS_MODULE,
	.class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
	.name		= "VIA i2c",
	.algo_data	= &bit_data,
};


static const struct pci_device_id vt586b_ids[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_82C586_3) },
	{ 0, }
};

MODULE_DEVICE_TABLE (pci, vt586b_ids);

static int vt586b_probe(struct pci_dev *dev, const struct pci_device_id *id)
{
	u16 base;
	u8 rev;
	int res;

	if (pm_io_base) {
		dev_err(&dev->dev, "i2c-via: Will only support one host\n");
		return -ENODEV;
	}

	pci_read_config_byte(dev, PM_CFG_REVID, &rev);

	switch (rev) {
	case 0x00:
		base = PM_CFG_IOBASE0;
		break;
	case 0x01:
	case 0x10:
		base = PM_CFG_IOBASE1;
		break;

	default:
		base = PM_CFG_IOBASE1;
		/* later revision */
	}

	pci_read_config_word(dev, base, &pm_io_base);
	pm_io_base &= (0xff << 8);

	if (!request_region(I2C_DIR, IOSPACE, vt586b_driver.name)) {
		dev_err(&dev->dev, "IO 0x%x-0x%x already in use\n", I2C_DIR, I2C_DIR + IOSPACE);
		return -ENODEV;
	}

	outb(inb(I2C_DIR) & ~(I2C_SDA | I2C_SCL), I2C_DIR);
	outb(inb(I2C_OUT) & ~(I2C_SDA | I2C_SCL), I2C_OUT);

	/* set up the sysfs linkage to our parent device */
	vt586b_adapter.dev.parent = &dev->dev;

	res = i2c_bit_add_bus(&vt586b_adapter);
	if ( res < 0 ) {
		release_region(I2C_DIR, IOSPACE);
		pm_io_base = 0;
		return res;
	}
	return 0;
}

static void vt586b_remove(struct pci_dev *dev)
{
	i2c_del_adapter(&vt586b_adapter);
	release_region(I2C_DIR, IOSPACE);
	pm_io_base = 0;
}


static struct pci_driver vt586b_driver = {
	.name		= "vt586b_smbus",
	.id_table	= vt586b_ids,
	.probe		= vt586b_probe,
	.remove		= vt586b_remove,
};

module_pci_driver(vt586b_driver);

MODULE_AUTHOR("Kyösti Mälkki <kmalkki@cc.hut.fi>");
MODULE_DESCRIPTION("i2c for Via vt82c586b southbridge");
MODULE_LICENSE("GPL");