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/*
* This file is part of the coreboot project.
*
* Copyright (C) 2005 Yinghai Lu <yinghailu@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc.
*/
#include <device/smbus_def.h>
#include "i82801ax.h"
int do_smbus_read_byte(u16 smbus_io_base, u8 device, u8 address);
static void smbus_delay(void)
{
inb(0x80);
}
static int smbus_wait_until_ready(u16 smbus_io_base)
{
unsigned loops = SMBUS_TIMEOUT;
unsigned char byte;
do {
smbus_delay();
if (--loops == 0)
break;
byte = inb(smbus_io_base + SMBHSTSTAT);
} while (byte & 1);
return loops ? 0 : -1;
}
static int smbus_wait_until_done(u16 smbus_io_base)
{
unsigned loops = SMBUS_TIMEOUT;
unsigned char byte;
do {
smbus_delay();
if (--loops == 0)
break;
byte = inb(smbus_io_base + SMBHSTSTAT);
} while ((byte & 1) || (byte & ~((1 << 6) | (1 << 0))) == 0);
return loops ? 0 : -1;
}
int do_smbus_read_byte(u16 smbus_io_base, u8 device, u8 address)
{
unsigned char global_status_register;
unsigned char byte;
if (smbus_wait_until_ready(smbus_io_base) < 0) {
return SMBUS_WAIT_UNTIL_READY_TIMEOUT;
}
/* 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 */
if (smbus_wait_until_done(smbus_io_base) < 0) {
return SMBUS_WAIT_UNTIL_DONE_TIMEOUT;
}
global_status_register = inb(smbus_io_base + SMBHSTSTAT);
/* Ignore the "In Use" status... */
global_status_register &= ~(3 << 5);
/* Read results of transaction */
byte = inb(smbus_io_base + SMBHSTDAT0);
if (global_status_register != (1 << 1)) {
return SMBUS_ERROR;
}
return byte;
}
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