src/southbridge/via/vt8231/early_smbus.c

#define SMBUS_IO_BASE 0x5000

#define SMBHSTSTAT 0x0
#define SMBSLVSTAT 0x1
#define SMBHSTCTL  0x2
#define SMBHSTCMD  0x3
#define SMBXMITADD 0x4
#define SMBHSTDAT0 0x5
#define SMBHSTDAT1 0x6
#define SMBBLKDAT  0x7
#define SMBSLVCTL  0x8
#define SMBTRNSADD 0x9
#define SMBSLVDATA 0xa
#define SMLINK_PIN_CTL 0xe
#define SMBUS_PIN_CTL  0xf

/* Define register settings */
#define HOST_RESET 0xff
#define READ_CMD  0x01		// 1 in the 0 bit of SMBHSTADD states to READ


#define SMBUS_TIMEOUT (100*1000*10)

static void enable_smbus(void)
{
	device_t dev;
	unsigned char c;
	/* Power management controller */
	dev = pci_locate_device(PCI_ID(0x1106, 0x8235), 0);

	if (dev == PCI_DEV_INVALID) {
		die("SMBUS controller not found\n");
	}
	// set IO base address to SMBUS_IO_BASE
	pci_write_config32(dev, 0x90, SMBUS_IO_BASE | 1);

	// Enable SMBus
	c = pci_read_config8(dev, 0xd2);
	c |= 5;
	pci_write_config8(dev, 0xd2, c);

	/* make it work for I/O ...
	 */
	dev = pci_locate_device(PCI_ID(0x1106, 0x8231), 0);
	c = pci_read_config8(dev, 4);
	c |= 1;
	pci_write_config8(dev, 4, c);
	print_debug_hex8(c);
	print_debug(" is the comm register\n");

	print_debug("SMBus controller enabled\n");
}


static inline void smbus_delay(void)
{
	outb(0x80, 0x80);
}

static int smbus_wait_until_active(void)
{
	unsigned long loops;
	loops = SMBUS_TIMEOUT;
	do {
		unsigned char val;
		smbus_delay();
		val = inb(SMBUS_IO_BASE + SMBHSTSTAT);
		if ((val & 1)) {
			break;
		}
	} while (--loops);
	return loops ? 0 : -4;
}

static int smbus_wait_until_ready(void)
{
	unsigned long loops;
	loops = SMBUS_TIMEOUT;
	do {
		unsigned char val;
		smbus_delay();
		val = inb(SMBUS_IO_BASE + SMBHSTSTAT);
		if ((val & 1) == 0) {
			break;
		}
		if (loops == (SMBUS_TIMEOUT / 2)) {
			outb(inb(SMBUS_IO_BASE + SMBHSTSTAT), SMBUS_IO_BASE + SMBHSTSTAT);
		}
	} while (--loops);
	return loops ? 0 : -2;
}

static int smbus_wait_until_done(void)
{
	unsigned long loops;
	loops = SMBUS_TIMEOUT;
	do {
		unsigned char val;
		smbus_delay();

		val = inb(SMBUS_IO_BASE + SMBHSTSTAT);
		if ((val & 1) == 0) {
			break;
		}
	} while (--loops);
	return loops ? 0 : -3;
}

#if 0
void smbus_reset(void)
{
	outb(HOST_RESET, SMBUS_IO_BASE + SMBHSTSTAT);
	outb(HOST_RESET, SMBUS_IO_BASE + SMBHSTSTAT);
	outb(HOST_RESET, SMBUS_IO_BASE + SMBHSTSTAT);
	outb(HOST_RESET, SMBUS_IO_BASE + SMBHSTSTAT);

	smbus_wait_until_ready();
	print_debug("After reset status ");
	print_debug_hex8(inb(SMBUS_IO_BASE + SMBHSTSTAT));
	print_debug("\n");
}
#endif

#if CONFIG_DEBUG_SMBUS
static void smbus_print_error(unsigned char host_status_register)
{

	print_err("smbus_error: ");
	print_err_hex8(host_status_register);
	print_err("\n");
	if (host_status_register & (1 << 4)) {
		print_err("Interrup/SMI# was Failed Bus Transaction\n");
	}
	if (host_status_register & (1 << 3)) {
		print_err("Bus Error\n");
	}
	if (host_status_register & (1 << 2)) {
		print_err("Device Error\n");
	}
	if (host_status_register & (1 << 1)) {
		print_err("Interrupt/SMI# was Successful Completion\n");
	}
	if (host_status_register & (1 << 0)) {
		print_err("Host Busy\n");
	}
}
#endif

/*
 * Copied from intel/i82801dbm early smbus code - suggested by rgm.
 * Modifications/check against i2c-viapro driver code from linux-2.4.22
 * and VT8231 Reference Docs - mw.
 */
static int smbus_read_byte(unsigned device, unsigned address)
{
	unsigned char global_status_register;
	unsigned char byte;

	if (smbus_wait_until_ready() < 0) {
		outb(inb(SMBUS_IO_BASE + SMBHSTSTAT), SMBUS_IO_BASE + SMBHSTSTAT);
		if (smbus_wait_until_ready() < 0) {
			return -2;
		}
	}

	/* setup transaction */
	/* disable interrupts */
	outb(inb(SMBUS_IO_BASE + SMBHSTCTL) & 0xfe, SMBUS_IO_BASE + SMBHSTCTL);
	/* set the device I'm talking too */
	outb(((device & 0x7f) << 1) | 1, SMBUS_IO_BASE + SMBXMITADD);
	/* set the command/address... */
	outb(address & 0xFF, SMBUS_IO_BASE + SMBHSTCMD);
	/* set up for a byte data read */
	outb((inb(SMBUS_IO_BASE + SMBHSTCTL) & 0xe3) | (0x2 << 2), SMBUS_IO_BASE + SMBHSTCTL);

	/* clear any lingering errors, so the transaction will run */
	outb(inb(SMBUS_IO_BASE + SMBHSTSTAT), SMBUS_IO_BASE + SMBHSTSTAT);

	/* clear the data byte... */
	outb(0, SMBUS_IO_BASE + SMBHSTDAT0);

	/* start a byte read, with interrupts disabled */
	outb((inb(SMBUS_IO_BASE + SMBHSTCTL) | 0x40), SMBUS_IO_BASE + SMBHSTCTL);
	/* poll for it to start */
	if (smbus_wait_until_active() < 0) {
		return -4;
	}

	/* poll for transaction completion */
	if (smbus_wait_until_done() < 0) {
		return -3;
	}

	/* Ignore the Host Busy & Command Complete ? */
	global_status_register = inb(SMBUS_IO_BASE + SMBHSTSTAT) & ~((1 << 1) | (1 << 0));

	/* read results of transaction */
	byte = inb(SMBUS_IO_BASE + SMBHSTDAT0);

	if (global_status_register != 0) {
		return -1;
	}
	return byte;
}

#if 0
/* SMBus routines borrowed from VIA's Trident Driver */
/* this works, so I am not going to touch it for now -- rgm */
static unsigned char smbus_read_byte(unsigned char devAdr, unsigned char bIndex)
{
	unsigned int i;
	unsigned char bData;
	unsigned char sts = 0;

	/* clear host status */
	outb(0xff, SMBUS_IO_BASE);

	/* check SMBUS ready */
	for (i = 0; i < SMBUS_TIMEOUT; i++)
		if ((inb(SMBUS_IO_BASE) & 0x01) == 0)
			break;

	/* set host command */
	outb(bIndex, SMBUS_IO_BASE + 3);

	/* set slave address */
	outb(devAdr | 0x01, SMBUS_IO_BASE + 4);

	/* start */
	outb(0x48, SMBUS_IO_BASE + 2);

	/* SMBUS Wait Ready */
	for (i = 0; i < SMBUS_TIMEOUT; i++)
		if (((sts = inb(SMBUS_IO_BASE)) & 0x01) == 0)
			break;
	if ((sts & ~3) != 0) {
		smbus_print_error(sts);
		return 0;
	}
	bData = inb(SMBUS_IO_BASE + 5);

	return bData;

}
#endif
/* for reference, here is the fancier version which we will use at some
 * point
 */
# if 0
int smbus_read_byte(unsigned device, unsigned address, unsigned char *result)
{
	unsigned char host_status_register;
	unsigned char byte;

	reset();

	smbus_wait_until_ready();

	/* setup transaction */
	/* disable interrupts */
	outb(inb(SMBUS_IO_BASE + SMBHSTCTL) & (~1), SMBUS_IO_BASE + SMBHSTCTL);
	/* set the device I'm talking too */
	outb(((device & 0x7f) << 1) | 1, SMBUS_IO_BASE + SMBXMITADD);
	/* set the command/address... */
	outb(address & 0xFF, SMBUS_IO_BASE + SMBHSTCMD);
	/* set up for a byte data read */
	outb((inb(SMBUS_IO_BASE + SMBHSTCTL) & 0xE3) | (0x2 << 2), SMBUS_IO_BASE + SMBHSTCTL);

	/* clear any lingering errors, so the transaction will run */
	outb(inb(SMBUS_IO_BASE + SMBHSTSTAT), SMBUS_IO_BASE + SMBHSTSTAT);

	/* clear the data byte... */
	outb(0, SMBUS_IO_BASE + SMBHSTDAT0);

	/* start the command */
	outb((inb(SMBUS_IO_BASE + SMBHSTCTL) | 0x40), SMBUS_IO_BASE + SMBHSTCTL);

	/* poll for transaction completion */
	smbus_wait_until_done();

	host_status_register = inb(SMBUS_IO_BASE + SMBHSTSTAT);

	/* Ignore the In Use Status... */
	host_status_register &= ~(1 << 6);

	/* read results of transaction */
	byte = inb(SMBUS_IO_BASE + SMBHSTDAT0);
	smbus_print_error(byte);

	*result = byte;
	return host_status_register != 0x02;
}


#endif