i3100: add smbus_write_byte()

Required for Supermicro X7DB8, which needs the FBDIMM clock generator
setup during romstage.

Change-Id: I30ca8354087e851487aee0614595782131d4d9bc
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Reviewed-on: http://review.coreboot.org/1116
Tested-by: build bot (Jenkins)

src/southbridge/intel/i3100/early_smbus.c

@@ -37,7 +37,12 @@ static void enable_smbus(void)
 	outb(0, SMBUS_IO_BASE + SMBHSTCTL);
 }
 
-static int smbus_read_byte(u32 device, u32 address)
+static __attribute__((unused)) int smbus_read_byte(u32 device, u32 address)
 {
 	return do_smbus_read_byte(SMBUS_IO_BASE, device, address);
 }
+
+static __attribute__((unused)) int smbus_write_byte(unsigned device, u8 address, u8 data)
+{
+	return do_smbus_write_byte(SMBUS_IO_BASE, device, address, data);
+}

src/southbridge/intel/i3100/smbus.c

@@ -41,8 +41,22 @@ static int lsmbus_read_byte(device_t dev, u8 address)
 	return do_smbus_read_byte(res->base, device, address);
 }
 
+static int lsmbus_write_byte(device_t dev, u8 address, u8 byte)
+{
+	u16 device;
+	struct resource *res;
+	struct bus *pbus;
+
+	device = dev->path.i2c.device;
+	pbus = get_pbus_smbus(dev);
+	res = find_resource(pbus->dev, 0x20);
+
+	return do_smbus_write_byte(res->base, device, address, byte);
+}
+
 static struct smbus_bus_operations lops_smbus_bus = {
 	.read_byte  = lsmbus_read_byte,
+	.write_byte = lsmbus_write_byte,
 };
 
 static void smbus_set_subsystem(device_t dev, unsigned vendor, unsigned device)

src/southbridge/intel/i3100/smbus.h

@@ -110,3 +110,46 @@ static int do_smbus_read_byte(u32 smbus_io_base, u16 device, u8 address)
 	}
 	return byte;
 }
+
+static  int do_smbus_write_byte(unsigned smbus_base, unsigned device, unsigned address, unsigned data)
+{
+	unsigned char global_status_register;
+
+	if (smbus_wait_until_ready(smbus_base) < 0)
+		return SMBUS_WAIT_UNTIL_READY_TIMEOUT;
+
+	/* Setup transaction */
+	/* Disable interrupts */
+	outb(inb(smbus_base + SMBHSTCTL) & (~1), smbus_base + SMBHSTCTL);
+	/* Set the device I'm talking too */
+	outb(((device & 0x7f) << 1) & ~0x01, smbus_base + SMBXMITADD);
+	/* Set the command/address... */
+	outb(address & 0xff, smbus_base + SMBHSTCMD);
+	/* Set up for a byte data read */
+	outb((inb(smbus_base + SMBHSTCTL) & 0xe3) | (0x2 << 2),
+	     (smbus_base + SMBHSTCTL));
+	/* Clear any lingering errors, so the transaction will run */
+	outb(inb(smbus_base + SMBHSTSTAT), smbus_base + SMBHSTSTAT);
+
+	/* Clear the data byte... */
+	outb(data, smbus_base + SMBHSTDAT0);
+
+	/* Start the command */
+	outb((inb(smbus_base + SMBHSTCTL) | 0x40),
+	     smbus_base + SMBHSTCTL);
+
+	/* Poll for transaction completion */
+	if (smbus_wait_until_done(smbus_base) < 0)
+		return SMBUS_WAIT_UNTIL_DONE_TIMEOUT;
+
+	global_status_register = inb(smbus_base + SMBHSTSTAT);
+
+	/* Ignore the "In Use" status... */
+	global_status_register &= ~(3 << 5);
+
+	/* Read results of transaction */
+	if (global_status_register != (1 << 1))
+		return SMBUS_ERROR;
+
+	return 0;
+}