2 * This file is part of the coreboot project.
4 * Copyright (C) 2005 Yinghai Lu <yinghailu@gmail.com>
5 * Copyright (C) 2009 coresystems GmbH
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; version 2 of the License.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
21 #include <device/smbus_def.h>
24 static void smbus_delay(void)
29 static int smbus_wait_until_ready(u16 smbus_base)
31 unsigned loops = SMBUS_TIMEOUT;
37 byte = inb(smbus_base + SMBHSTSTAT);
39 return loops ? 0 : -1;
42 static int smbus_wait_until_done(u16 smbus_base)
44 unsigned loops = SMBUS_TIMEOUT;
50 byte = inb(smbus_base + SMBHSTSTAT);
51 } while ((byte & 1) || (byte & ~((1 << 6) | (1 << 0))) == 0);
52 return loops ? 0 : -1;
55 static int do_smbus_read_byte(unsigned smbus_base, unsigned device, unsigned address)
57 unsigned char global_status_register;
60 if (smbus_wait_until_ready(smbus_base) < 0) {
61 return SMBUS_WAIT_UNTIL_READY_TIMEOUT;
63 /* Setup transaction */
64 /* Disable interrupts */
65 outb(inb(smbus_base + SMBHSTCTL) & (~1), smbus_base + SMBHSTCTL);
66 /* Set the device I'm talking too */
67 outb(((device & 0x7f) << 1) | 1, smbus_base + SMBXMITADD);
68 /* Set the command/address... */
69 outb(address & 0xff, smbus_base + SMBHSTCMD);
70 /* Set up for a byte data read */
71 outb((inb(smbus_base + SMBHSTCTL) & 0xe3) | (0x2 << 2),
72 (smbus_base + SMBHSTCTL));
73 /* Clear any lingering errors, so the transaction will run */
74 outb(inb(smbus_base + SMBHSTSTAT), smbus_base + SMBHSTSTAT);
76 /* Clear the data byte... */
77 outb(0, smbus_base + SMBHSTDAT0);
79 /* Start the command */
80 outb((inb(smbus_base + SMBHSTCTL) | 0x40),
81 smbus_base + SMBHSTCTL);
83 /* Poll for transaction completion */
84 if (smbus_wait_until_done(smbus_base) < 0) {
85 return SMBUS_WAIT_UNTIL_DONE_TIMEOUT;
88 global_status_register = inb(smbus_base + SMBHSTSTAT);
90 /* Ignore the "In Use" status... */
91 global_status_register &= ~(3 << 5);
93 /* Read results of transaction */
94 byte = inb(smbus_base + SMBHSTDAT0);
95 if (global_status_register != (1 << 1)) {