coreboot: Add generic early SMBus API

Early SMBUS code with similar functionality is duplicated for all
southbridges. Add a generic SMBus API (function declarations) designed to
unify the early SMBus structure.

This patch only adds the API. It does not implement any hardware-specific
bits.

Change-Id: I0861b7a3f098115182ae6de9f016dd671c500bad
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/143
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/device/early_smbus.h

@@ -0,0 +1,73 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2011  Alexandru Gagniuc <mr.nuke.me@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, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * @file early_smbus.h
+ *
+ * This file defines a common API for accessing the SMBus during early
+ * initialization. It defines the prototypes for common SMBus functions. The
+ * actual implementations are hardware-dependent.
+ *
+ * The first parameter of all SMBus functions take a u32 value smbus_dev which
+ * represents some information on how to access the device, and is
+ * implementation defined. Usually, it just contains the IO base for the smbus.
+ * To get this argument @ref smbus_get_device() can be used.
+ *
+ * The header only defines the prototypes. Several steps are needed to use
+ * these:
+ *
+ * 1. Include this header
+ * @code{.c}
+ *	#include <device/early_smbus.h>
+ * @endcode
+ *
+ * 2. Implement early_smbus.c for the hardware, or find a compatible
+ * implementation.
+ *
+ * 3. Link against the file that implements these functions. In the Makefile.inc
+ * of the chipset, add:
+ * @code
+ *	romstage-y += ./path/to/early_smbus.c
+ * @endcode
+ */
+
+#ifndef DEVICE_EARLY_SMBUS_H
+#define DEVICE_EARLY_SMBUS_H
+
+#include <stdint.h>
+
+/**
+ * \brief printk macro for SMBus debugging
+ */
+#if defined(CONFIG_DEBUG_SMBUS_SETUP) && (CONFIG_DEBUG_SMBUS_SETUP)
+#define printsmbus(x, ...) printk(BIOS_DEBUG, x, ##__VA_ARGS__)
+#else
+#define printsmbus(x, ...)
+#endif
+
+u32 smbus_get_device(void);
+void smbus_reset(u32 smbus_dev);
+int smbus_print_error(u32 smbus_dev, u8 host_status, int loops);
+int smbus_is_busy(u32 smbus_dev);
+int smbus_wait_until_ready(u32 smbus_dev);
+u8 smbus_read_byte(u32 smbus_dev, u8 addr, u8 offset);
+
+void smbus_delay(void);
+
+#endif				/* DEVICE_EARLY_SMBUS_H */