src/southbridge/via/vt8235/early_smbus.c

#define SMBUS_IO_BASE 0xf00

#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)

#define  I2C_TRANS_CMD          0x40
#define  CLOCK_SLAVE_ADDRESS    0x69

static void enable_smbus(void)
{
	device_t dev;
	unsigned char c;
	int i;

	/* Power management controller */
	dev = pci_locate_device(PCI_ID(PCI_VENDOR_ID_VIA,
				PCI_DEVICE_ID_VIA_8235), 0);

	if (dev == PCI_DEV_INVALID) {
		die("SMBUS controller not found\n");
	}

	// set IO base address to SMBUS_IO_BASE
	pci_write_config16(dev, 0xd0, SMBUS_IO_BASE | 1);

	// Enable SMBus
	pci_write_config8(dev, 0xd2, (0x4 << 1) | 1);

	/* make it work for I/O ...
	 */
	pci_write_config16(dev, 4, 1);

	/* FIX for half baud rate problem */
	/* let clocks and the like settle */
	/* as yet arbitrary count - 1000 is too little 5000 works */
	for(i = 0 ; i < 5000 ; i++)
		outb(0x80,0x80);

	/*
	 * The VT1211 serial port needs 48 mhz clock, on power up it is getting
	 *  only 24 mhz, there is some mysterious device on the smbus that can
	 *  fix this...this code below does it.
	 *  */
	outb(0xff, SMBUS_IO_BASE+SMBHSTSTAT);
	outb(0x7f, SMBUS_IO_BASE+SMBHSTDAT0);
	outb(0x83, SMBUS_IO_BASE+SMBHSTCMD);
	outb(CLOCK_SLAVE_ADDRESS<<1 , SMBUS_IO_BASE+SMBXMITADD);
	outb(8 | I2C_TRANS_CMD, SMBUS_IO_BASE+SMBHSTCTL);

	for (;;) {
		c = inb(SMBUS_IO_BASE+SMBHSTSTAT);
		if ((c & 1) == 0)
			break;
	}
}


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

static int smbus_wait_until_ready(void)
{
	unsigned char c;
	unsigned long loops;
	loops = SMBUS_TIMEOUT;
	do {
		smbus_delay();
		c = inb(SMBUS_IO_BASE + SMBHSTSTAT);
		while((c & 1) == 1) {
			print_debug("c is ");
			print_debug_hex8(c);
			print_debug("\n");
			c = inb(SMBUS_IO_BASE + SMBHSTSTAT);
			/* nop */
		}

	} while(--loops);
	return loops?0:-1;
}

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");
}



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

		byte = inb(SMBUS_IO_BASE + SMBHSTSTAT);
		if (byte & 1)
			break;

	} while(--loops);
	return loops?0:-1;
}

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");
	}
}


/* 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 short i;
	unsigned char  bData;
	unsigned char  sts = 0;

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

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

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

	/* set slave address */
	outb((devAdr << 1) | 0x01, SMBUS_IO_BASE+4);

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

	/* SMBUS Wait Ready */
	for ( i = 0; i < 0xFFFF; i++ )
		if ( ((sts = (inb(SMBUS_IO_BASE) & 0x1f)) & 0x01) == 0 )
			break;

	if ((sts & ~3) != 0) {
		smbus_print_error(sts);
		return 0;
	}
	bData=inb(SMBUS_IO_BASE+5);

	return bData;

}

/* 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