Patch set updated for coreboot: 06780d0 early_smbus: Add early SMBUS implementation for VIA chipsets

[Alexandru Gagniuc]

Alexandru Gagniuc ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/144

-gerrit

commit 06780d063b781d9650027bc958443167333b8b2f
Author: Alexandru Gagniuc 
Date:   Tue May 21 12:35:08 2013 -0500

early_smbus: Add early SMBUS implementation for VIA chipsets

Add a common implementation of SMBUS functionality for early chipsets. Note
    however, that existing via chipsets are not ported to this code. Porting
    will require hardware testing to make sure everything is fine.

This code is used in the VIA VX900 branch.

Change-Id: If5ad8cd0942ac02d358a0139967e7d85d395660f
    Signed-off-by: Alexandru Gagniuc 
---
 src/southbridge/via/common/early_smbus.c | 176 +++++++++++++++++++++++++++++++
 1 file changed, 176 insertions(+)

diff --git a/src/southbridge/via/common/early_smbus.c b/src/southbridge/via/common/early_smbus.c
new file mode 100644
index 0000000..06f0a8a
--- /dev/null
+++ b/src/southbridge/via/common/early_smbus.c
@@ -0,0 +1,176 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2011-2013  Alexandru Gagniuc 
+ *
+ * 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 via_early_sambus.c
+ *
+ * This file defines the implementations for the functions defined in 
+ * device/early/smbus.h
+ *
+ * These implementations work with most via chipsets. Any VIA port should try
+ * to use these. Makefile.inc needs to be adapted to link against this file
+ * during romstage:
+ * @code
+ *	romstage-y += ./../../../southbridge/via/common/early_smbus.c
+ * @endcode
+ *
+ * These functions are marked weak in the event that one or more might need to
+ * be overridden. This may be the case when, for example, a chipset needs a
+ * longer delay for a specific operation.
+ */
+
+#include <device/early_smbus.h>
+
+#include <arch/io.h>
+
+/**
+ * \brief SMBUS IO ports in relation to the base IO port
+ */
+#define SMBHSTSTAT(base)		(u16)(u32)base + 0x0
+#define SMBSLVSTAT(base)		(u16)(u32)base + 0x1
+#define SMBHSTCTL(base)			(u16)(u32)base + 0x2
+#define SMBHSTCMD(base)			(u16)(u32)base + 0x3
+#define SMBXMITADD(base)		(u16)(u32)base + 0x4
+#define SMBHSTDAT0(base)		(u16)(u32)base + 0x5
+#define SMBHSTDAT1(base)		(u16)(u32)base + 0x6
+#define SMBBLKDAT(base)			(u16)(u32)base + 0x7
+#define SMBSLVCTL(base)			(u16)(u32)base + 0x8
+#define SMBTRNSADD(base)		(u16)(u32)base + 0x9
+#define SMBSLVDATA (base)		(u16)(u32)base + 0xa
+
+#define SMBUS_TIMEOUT		(100*1000*10)
+
+/**
+ * \brief Brief delay for SMBUS transactions
+ */
+void smbus_delay(void)
+{
+	inb(0x80);
+}
+
+/**
+ * \brief Clear the SMBUS host status register
+ *
+ * @param smbus_dev The base SMBUS IO port
+ */
+__attribute__((weak))
+void smbus_reset(u32 smbus_dev)
+{
+	outb(0xdf, SMBHSTSTAT(smbus_dev));
+}
+
+/**
+ * \brief Print an error, should it occur. If no error, just exit.
+ *
+ * @param smbus_dev The base SMBUS IO port
+ * @param host_status The data returned on the host status register after
+ *		      a transaction is processed.
+ * @param loops The number of times a transaction was attempted.
+ * @return	0 if no error occurred
+ * 		1 if an error was detected
+ */
+__attribute__((weak))
+int smbus_print_error(u32 smbus_dev, u8 host_status, int loops)
+{
+	/* Check if there actually was an error. */
+	if ((host_status == 0x00 || host_status == 0x40 ||
+		host_status == 0x42) && (loops < SMBUS_TIMEOUT))
+		return 0;
+	
+	if (loops >= SMBUS_TIMEOUT)
+		printsmbus("SMBus timeout\n");
+	if (host_status & (1 << 4))
+		printsmbus("Interrupt/SMI# was Failed Bus Transaction\n");
+	if (host_status & (1 << 3))
+		printsmbus("Bus error\n");
+	if (host_status & (1 << 2))
+		printsmbus("Device error\n");
+	if (host_status & (1 << 1))
+		printsmbus("Interrupt/SMI# completed successfully\n");
+	if (host_status & (1 << 0))
+		printsmbus("Host busy\n");
+	return 1;
+}
+
+/**
+ * \brief Checks if the SMBUS is currently busy with a transaction
+ *
+ * @param smbus_dev The base SMBUS IO port
+ */
+__attribute__((weak))
+int smbus_is_busy(u32 smbus_dev)
+{
+	/* Check if bit 0 of the status register is 1 (busy) or 0 (ready) */
+	return ( (inb(SMBHSTSTAT(smbus_dev)) & (1 << 0)) == 1);
+}
+
+/**
+ * \brief Wait for the SMBUS to become ready to process a new transaction.
+ *
+ * @param smbus_dev The base SMBUS IO port
+ */
+__attribute__((weak))
+int smbus_wait_until_ready(u32 smbus_dev)
+{
+	int loops;
+	
+	printsmbus("Waiting until SMBus ready\n");
+	
+	/* Loop up to SMBUS_TIMEOUT times, waiting for bit 0 of the
+	 * SMBus Host Status register to go to 0, indicating the operation
+	 * was completed successfully. I don't remember why I did it this way,
+	 * but I think it was because ROMCC was running low on registers */
+	loops = 0;
+	while (smbus_is_busy(smbus_dev) && loops < SMBUS_TIMEOUT)
+		++loops;
+	
+	return smbus_print_error(smbus_dev, inb(SMBHSTSTAT(smbus_dev)), loops);
+}
+
+/**
+ * \brief Read a byte from the SMBUS.
+ *
+ * @param smbus_dev The base SMBUS IO port
+ * @param addr The address location of the DIMM on the SMBus.
+ * @param offset The offset the data is located at.
+ */
+__attribute__((weak))
+u8 smbus_read_byte(u32 smbus_dev, u8 addr, u8 offset)
+{
+	u8 val;
+	
+	/* Initialize SMBUS sequence */
+	smbus_reset(smbus_dev);
+	/* Clear host data port. */
+	outb(0x00, SMBHSTDAT0(smbus_dev));
+	
+	smbus_wait_until_ready(smbus_dev);
+	
+	/* Actual addr to reg format. */
+	addr = (addr << 1);
+	addr |= 1; /* read command */
+	outb(addr, SMBXMITADD(smbus_dev));
+	outb(offset, SMBHSTCMD(smbus_dev));
+	/* Start transaction, byte data read. */
+	outb(0x48, SMBHSTCTL(smbus_dev));
+	smbus_wait_until_ready(smbus_dev);
+	
+	val = inb(SMBHSTDAT0(smbus_dev));
+	return val;
+}