sb600spi.c

/*
 * This file is part of the flashrom project.
 *
 * Copyright (C) 2008 Wang Qingpei <Qingpei.Wang@amd.com>
 * Copyright (C) 2008 Joe Bao <Zheng.Bao@amd.com>
 * Copyright (C) 2008 Advanced Micro Devices, Inc.
 * Copyright (C) 2009, 2010, 2013 Carl-Daniel Hailfinger
 * Copyright (C) 2013 Stefan Tauner
 *
 * 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.
 */

#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#include "flash.h"
#include "programmer.h"
#include "hwaccess_physmap.h"
#include "spi.h"
#include "platform/pci.h"

/* This struct is unused, but helps visualize the SB600 SPI BAR layout.
 *struct sb600_spi_controller {
 *	unsigned int spi_cntrl0;	/ * 00h * /
 *	unsigned int restrictedcmd1;	/ * 04h * /
 *	unsigned int restrictedcmd2;	/ * 08h * /
 *	unsigned int spi_cntrl1;	/ * 0ch * /
 *	unsigned int spi_cmdvalue0;	/ * 10h * /
 *	unsigned int spi_cmdvalue1;	/ * 14h * /
 *	unsigned int spi_cmdvalue2;	/ * 18h * /
 *	unsigned int spi_fakeid;	/ * 1Ch * /
 *};
 */

static uint8_t *sb600_spibar = NULL;
enum amd_chipset {
	CHIPSET_AMD_UNKNOWN,
	CHIPSET_SB6XX,
	CHIPSET_SB7XX, /* SP5100 too */
	CHIPSET_SB89XX, /* Hudson-1 too */
	CHIPSET_HUDSON234,
	CHIPSET_BOLTON,
	CHIPSET_YANGTZE,
	CHIPSET_PROMONTORY,
};
static enum amd_chipset amd_gen = CHIPSET_AMD_UNKNOWN;

#define FIFO_SIZE_OLD		8
#define FIFO_SIZE_YANGTZE	71

static int sb600_spi_send_command(const struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
				  const unsigned char *writearr, unsigned char *readarr);
static int spi100_spi_send_command(const struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
				  const unsigned char *writearr, unsigned char *readarr);

static struct spi_master spi_master_sb600 = {
	.max_data_read	= FIFO_SIZE_OLD,
	.max_data_write	= FIFO_SIZE_OLD - 3,
	.command	= sb600_spi_send_command,
	.multicommand	= default_spi_send_multicommand,
	.read		= default_spi_read,
	.write_256	= default_spi_write_256,
	.probe_opcode	= default_spi_probe_opcode,
};

static struct spi_master spi_master_yangtze = {
	.max_data_read	= FIFO_SIZE_YANGTZE - 3, /* Apparently the big SPI 100 buffer is not a ring buffer. */
	.max_data_write	= FIFO_SIZE_YANGTZE - 3,
	.command	= spi100_spi_send_command,
	.multicommand	= default_spi_send_multicommand,
	.read		= default_spi_read,
	.write_256	= default_spi_write_256,
	.probe_opcode	= default_spi_probe_opcode,
};

static int find_smbus_dev_rev(uint16_t vendor, uint16_t device)
{
	struct pci_dev *smbus_dev = pcidev_find(vendor, device);
	if (!smbus_dev) {
		msg_pdbg("No SMBus device with ID %04X:%04X found.\n", vendor, device);
		msg_perr("ERROR: SMBus device not found. Not enabling SPI.\n");
		return -1;
	}
	return pci_read_byte(smbus_dev, PCI_REVISION_ID);
}

/* Determine the chipset's version and identify the respective SMBUS device. */
static int determine_generation(struct pci_dev *dev)
{
	amd_gen = CHIPSET_AMD_UNKNOWN;
	msg_pdbg2("Trying to determine the generation of the SPI interface... ");
	if (dev->device_id == 0x438d) {
		amd_gen = CHIPSET_SB6XX;
		msg_pdbg("SB6xx detected.\n");
	} else if (dev->device_id == 0x439d) {
		int rev = find_smbus_dev_rev(0x1002, 0x4385);
		if (rev < 0)
			return -1;
		if (rev >= 0x39 && rev <= 0x3D) {
			amd_gen = CHIPSET_SB7XX;
			msg_pdbg("SB7xx/SP5100 detected.\n");
		} else if (rev >= 0x40 && rev <= 0x42) {
			amd_gen = CHIPSET_SB89XX;
			msg_pdbg("SB8xx/SB9xx/Hudson-1 detected.\n");
		} else {
			msg_pwarn("SB device found but SMBus revision 0x%02x does not match known values.\n"
				  "Assuming SB8xx/SB9xx/Hudson-1.\n"
				  "Please send a log to flashprog@flashprog.org\n",
				  rev);
			amd_gen = CHIPSET_SB89XX;
		}
	} else if (dev->device_id == 0x780e) {
		/* The PCI ID of the LPC bridge doesn't change between Hudson-2/3/4 and Yangtze (Kabini/Temash)
		 * although they use different SPI interfaces. */
		int rev = find_smbus_dev_rev(0x1022, 0x780B);
		if (rev < 0)
			return -1;
		if (rev >= 0x11 && rev <= 0x15) {
			amd_gen = CHIPSET_HUDSON234;
			msg_pdbg("Hudson-2/3/4 detected.\n");
		} else if (rev == 0x16) {
			amd_gen = CHIPSET_BOLTON;
			msg_pdbg("Bolton detected.\n");
		} else if ((rev >= 0x39 && rev <= 0x3A) || rev == 0x42) {
			amd_gen = CHIPSET_YANGTZE;
			msg_pdbg("Yangtze detected.\n");
		} else {
			msg_pwarn("FCH device found but SMBus revision 0x%02x does not match known values.\n"
				  "Please report this to flashprog@flashprog.org and include this\n"
				  "log and the output of lspci -nnvx, thanks!.\n", rev);
		}
	} else if (dev->device_id == 0x790e) {
		int rev = find_smbus_dev_rev(0x1022, 0x790B);
		if (rev < 0)
			return -1;
		if (rev == 0x4a) {
			amd_gen = CHIPSET_YANGTZE;
			msg_pdbg("Yangtze detected.\n");
		} else if (rev == 0x4b) {
			amd_gen = CHIPSET_PROMONTORY;
			msg_pdbg("Promontory detected.\n");
		} else {
			msg_pwarn("FCH device found but SMBus revision 0x%02x does not match known values.\n"
				  "Please report this to flashprog@flashprog.org and include this\n"
				  "log and the output of lspci -nnvx, thanks!.\n", rev);
		}


	} else
		msg_pwarn("%s: Unknown LPC device %" PRIx16 ":%" PRIx16 ".\n"
			  "Please report this to flashprog@flashprog.org and include this\n"
			  "log and the output of lspci -nnvx, thanks!\n",
			  __func__, dev->vendor_id, dev->device_id);
	if (amd_gen == CHIPSET_AMD_UNKNOWN) {
		msg_perr("Could not determine chipset generation.");
		return -1;
	}
	return 0;
}

static void reset_internal_fifo_pointer(void)
{
	mmio_writeb(mmio_readb(sb600_spibar + 2) | 0x10, sb600_spibar + 2);

	/* FIXME: This loop needs a timeout and a clearer message. */
	while (mmio_readb(sb600_spibar + 0xD) & 0x7)
		msg_pspew("reset\n");
}

static int compare_internal_fifo_pointer(uint8_t want)
{
	uint8_t have = mmio_readb(sb600_spibar + 0xd) & 0x07;
	want %= FIFO_SIZE_OLD;
	if (have != want) {
		msg_perr("AMD SPI FIFO pointer corruption! Pointer is %d, wanted %d\n", have, want);
		msg_perr("Something else is accessing the flash chip and causes random corruption.\n"
			 "Please stop all applications and drivers and IPMI which access the flash chip.\n");
		return 1;
	} else {
		msg_pspew("AMD SPI FIFO pointer is %d, wanted %d\n", have, want);
		return 0;
	}
}

/* Check the number of bytes to be transmitted and extract opcode. */
static int check_readwritecnt(const struct flashctx *flash, unsigned int writecnt, unsigned int readcnt)
{
	unsigned int maxwritecnt = flash->mst.spi->max_data_write + 3;
	if (writecnt > maxwritecnt) {
		msg_pinfo("%s: SPI controller can not send %d bytes, it is limited to %d bytes\n",
			  __func__, writecnt, maxwritecnt);
		return SPI_INVALID_LENGTH;
	}

	unsigned int maxreadcnt = flash->mst.spi->max_data_read;
	if (readcnt > maxreadcnt) {
		msg_pinfo("%s: SPI controller can not receive %d bytes, it is limited to %d bytes\n",
			  __func__, readcnt, maxreadcnt);
		return SPI_INVALID_LENGTH;
	}
	return 0;
}

static void execute_command(void)
{
	msg_pspew("Executing... ");
	mmio_writeb(mmio_readb(sb600_spibar + 2) | 1, sb600_spibar + 2);
	while (mmio_readb(sb600_spibar + 2) & 1)
		;
	msg_pspew("done\n");
}

static int sb600_spi_send_command(const struct flashctx *flash, unsigned int writecnt,
				  unsigned int readcnt,
				  const unsigned char *writearr,
				  unsigned char *readarr)
{
	/* First byte is cmd which can not be sent through the FIFO. */
	unsigned char cmd = *writearr++;
	writecnt--;
	msg_pspew("%s, cmd=0x%02x, writecnt=%d, readcnt=%d\n", __func__, cmd, writecnt, readcnt);
	mmio_writeb(cmd, sb600_spibar + 0);

	int ret = check_readwritecnt(flash, writecnt, readcnt);
	if (ret != 0)
		return ret;

	/* This is a workaround for a bug in SPI controller. If we only send
	 * an opcode and no additional data/address, the SPI controller will
	 * read one byte too few from the chip. Basically, the last byte of
	 * the chip response is discarded and will not end up in the FIFO.
	 * It is unclear if the CS# line is set high too early as well.
	 */
	unsigned int readoffby1 = (writecnt > 0) ? 0 : 1;
	uint8_t readwrite = (readcnt + readoffby1) << 4 | (writecnt);
	mmio_writeb(readwrite, sb600_spibar + 1);

	reset_internal_fifo_pointer();
	msg_pspew("Filling FIFO: ");
	unsigned int count;
	for (count = 0; count < writecnt; count++) {
		msg_pspew("[%02x]", writearr[count]);
		mmio_writeb(writearr[count], sb600_spibar + 0xC);
	}
	msg_pspew("\n");
	if (compare_internal_fifo_pointer(writecnt))
		return SPI_PROGRAMMER_ERROR;

	/*
	 * We should send the data in sequence, which means we need to reset
	 * the FIFO pointer to the first byte we want to send.
	 */
	reset_internal_fifo_pointer();
	execute_command();
	if (compare_internal_fifo_pointer(writecnt + readcnt))
		return SPI_PROGRAMMER_ERROR;

	/*
	 * After the command executed, we should find out the index of the
	 * received byte. Here we just reset the FIFO pointer and skip the
	 * writecnt.
	 * It would be possible to increase the FIFO pointer by one instead
	 * of reading and discarding one byte from the FIFO.
	 * The FIFO is implemented on top of an 8 byte ring buffer and the
	 * buffer is never cleared. For every byte that is shifted out after
	 * the opcode, the FIFO already stores the response from the chip.
	 * Usually, the chip will respond with 0x00 or 0xff.
	 */
	reset_internal_fifo_pointer();

	/* Skip the bytes we sent. */
	msg_pspew("Skipping: ");
	for (count = 0; count < writecnt; count++) {
		msg_pspew("[%02x]", mmio_readb(sb600_spibar + 0xC));
	}
	msg_pspew("\n");
	if (compare_internal_fifo_pointer(writecnt))
		return SPI_PROGRAMMER_ERROR;

	msg_pspew("Reading FIFO: ");
	for (count = 0; count < readcnt; count++) {
		readarr[count] = mmio_readb(sb600_spibar + 0xC);
		msg_pspew("[%02x]", readarr[count]);
	}
	msg_pspew("\n");
	if (compare_internal_fifo_pointer(writecnt+readcnt))
		return SPI_PROGRAMMER_ERROR;

	if (mmio_readb(sb600_spibar + 1) != readwrite) {
		msg_perr("Unexpected change in AMD SPI read/write count!\n");
		msg_perr("Something else is accessing the flash chip and causes random corruption.\n"
			 "Please stop all applications and drivers and IPMI which access the flash chip.\n");
		return SPI_PROGRAMMER_ERROR;
	}

	return 0;
}

static int spi100_spi_send_command(const struct flashctx *flash, unsigned int writecnt,
				  unsigned int readcnt,
				  const unsigned char *writearr,
				  unsigned char *readarr)
{
	/* First byte is cmd which can not be sent through the buffer. */
	unsigned char cmd = *writearr++;
	writecnt--;
	msg_pspew("%s, cmd=0x%02x, writecnt=%d, readcnt=%d\n", __func__, cmd, writecnt, readcnt);
	mmio_writeb(cmd, sb600_spibar + 0);

	int ret = check_readwritecnt(flash, writecnt, readcnt);
	if (ret != 0)
		return ret;

	/* Use the extended TxByteCount and RxByteCount registers. */
	mmio_writeb(writecnt, sb600_spibar + 0x48);
	mmio_writeb(readcnt, sb600_spibar + 0x4b);

	msg_pspew("Filling buffer: ");
	unsigned int count;
	for (count = 0; count < writecnt; count++) {
		msg_pspew("[%02x]", writearr[count]);
		mmio_writeb(writearr[count], sb600_spibar + 0x80 + count);
	}
	msg_pspew("\n");

	execute_command();

	msg_pspew("Reading buffer: ");
	for (count = 0; count < readcnt; count++) {
		readarr[count] = mmio_readb(sb600_spibar + 0x80 + (writecnt + count) % FIFO_SIZE_YANGTZE);
		msg_pspew("[%02x]", readarr[count]);
	}
	msg_pspew("\n");

	return 0;
}

struct spispeed {
	const char *const name;
	const uint8_t speed;
};

static const struct spispeed spispeeds[] = {
	{ "66 MHz",	0x00 },
	{ "33 MHz",	0x01 },
	{ "22 MHz",	0x02 },
	{ "16.5 MHz",	0x03 },
	{ "100 MHz",	0x04 },
	{ "Reserved",	0x05 },
	{ "Reserved",	0x06 },
	{ "800 kHz",	0x07 },
};

static int set_speed(struct pci_dev *dev, const struct spispeed *spispeed)
{
	bool success = false;
	uint8_t speed = spispeed->speed;

	msg_pdbg("Setting SPI clock to %s (0x%x).\n", spispeed->name, speed);
	if (amd_gen >= CHIPSET_YANGTZE) {
		rmmio_writew((speed << 12) | (speed << 8) | (speed << 4) | speed, sb600_spibar + 0x22);
		uint16_t tmp = mmio_readw(sb600_spibar + 0x22);
		success = (((tmp >> 12) & 0xf) == speed && ((tmp >> 8) & 0xf) == speed &&
			   ((tmp >> 4) & 0xf) == speed && ((tmp >> 0) & 0xf) == speed);
	} else {
		rmmio_writeb((mmio_readb(sb600_spibar + 0xd) & ~(0x3 << 4)) | (speed << 4), sb600_spibar + 0xd);
		success = (speed == ((mmio_readb(sb600_spibar + 0xd) >> 4) & 0x3));
	}

	if (!success) {
		msg_perr("Setting SPI clock failed.\n");
		return 1;
	}
	return 0;
}

static int set_mode(struct pci_dev *dev, uint8_t read_mode)
{
	uint32_t tmp = mmio_readl(sb600_spibar + 0x00);
	tmp &= ~(0x6 << 28 | 0x1 << 18); /* Clear mode bits */
	tmp |= ((read_mode & 0x6) << 28) | ((read_mode & 0x1) << 18);
	rmmio_writel(tmp, sb600_spibar + 0x00);
	if (tmp != mmio_readl(sb600_spibar + 0x00))
		return 1;
	return 0;
}

static int handle_speed(struct pci_dev *dev)
{
	uint32_t tmp;
	uint8_t spispeed_idx = 3; /* Default to 16.5 MHz */

	char *spispeed = extract_programmer_param("spispeed");
	if (spispeed != NULL) {
		unsigned int i;
		for (i = 0; i < ARRAY_SIZE(spispeeds); i++) {
			if (strcasecmp(spispeeds[i].name, spispeed) == 0) {
				spispeed_idx = i;
				break;
			}
		}
		/* "reserved" is not a valid speed.
		 * Error out on speeds not present in the spispeeds array.
		 * Only Yangtze supports the second half of indices.
		 * No 66 MHz before SB8xx. */
		if ((strcasecmp(spispeed, "reserved") == 0) ||
		    (i == ARRAY_SIZE(spispeeds)) ||
		    (amd_gen < CHIPSET_YANGTZE && spispeed_idx > 3) ||
		    (amd_gen < CHIPSET_SB89XX && spispeed_idx == 0)) {
			msg_perr("Error: Invalid spispeed value: '%s'.\n", spispeed);
			free(spispeed);
			return 1;
		}
		free(spispeed);
	}

	/* See the chipset support matrix for SPI Base_Addr below for an explanation of the symbols used.
	 * bit   6xx   7xx/SP5100  8xx             9xx  hudson1  hudson234  bolton/yangtze
	 * 18    rsvd  <-          fastReadEnable  ?    <-       ?          SpiReadMode[0]
	 * 29:30 rsvd  <-          <-              ?    <-       ?          SpiReadMode[2:1]
	 */
	if (amd_gen >= CHIPSET_BOLTON) {
		static const char *spireadmodes[] = {
			"Normal (up to 33 MHz)", /* 0 */
			"Reserved",		 /* 1 */
			"Dual IO (1-1-2)",	 /* 2 */
			"Quad IO (1-1-4)",	 /* 3 */
			"Dual IO (1-2-2)",	 /* 4 */
			"Quad IO (1-4-4)",	 /* 5 */
			"Normal (up to 66 MHz)", /* 6 */
			"Fast Read",		 /* 7 (Not defined in the Bolton datasheet.) */
		};
		tmp = mmio_readl(sb600_spibar + 0x00);
		uint8_t read_mode = ((tmp >> 28) & 0x6) | ((tmp >> 18) & 0x1);
		msg_pdbg("SpiReadMode=%s (%i)\n", spireadmodes[read_mode], read_mode);
		if (read_mode != 6) {
			read_mode = 6; /* Default to "Normal (up to 66 MHz)" */
			if (set_mode(dev, read_mode) != 0) {
				msg_perr("Setting read mode to \"%s\" failed.\n", spireadmodes[read_mode]);
				return 1;
			}
			msg_pdbg("Setting read mode to \"%s\" succeeded.\n", spireadmodes[read_mode]);
		}

		if (amd_gen >= CHIPSET_YANGTZE) {
			tmp = mmio_readb(sb600_spibar + 0x20);
			msg_pdbg("UseSpi100 is %sabled\n", (tmp & 0x1) ? "en" : "dis");
			if ((tmp & 0x1) == 0) {
				rmmio_writeb(tmp | 0x1, sb600_spibar + 0x20);
				tmp = mmio_readb(sb600_spibar + 0x20) & 0x1;
				if (tmp == 0) {
					msg_perr("Enabling Spi100 failed.\n");
					return 1;
				}
				msg_pdbg("Enabling Spi100 succeeded.\n");
			}

			tmp = mmio_readw(sb600_spibar + 0x22); /* SPI 100 Speed Config */
			msg_pdbg("NormSpeedNew is %s\n", spispeeds[(tmp >> 12) & 0xf].name);
			msg_pdbg("FastSpeedNew is %s\n", spispeeds[(tmp >> 8) & 0xf].name);
			msg_pdbg("AltSpeedNew is %s\n", spispeeds[(tmp >> 4) & 0xf].name);
			msg_pdbg("TpmSpeedNew is %s\n", spispeeds[(tmp >> 0) & 0xf].name);
		}
	} else {
		if (amd_gen >= CHIPSET_SB89XX && amd_gen <= CHIPSET_HUDSON234) {
			bool fast_read = (mmio_readl(sb600_spibar + 0x00) >> 18) & 0x1;
			msg_pdbg("Fast Reads are %sabled\n", fast_read ? "en" : "dis");
			if (fast_read) {
				msg_pdbg("Disabling them temporarily.\n");
				rmmio_writel(mmio_readl(sb600_spibar + 0x00) & ~(0x1 << 18),
					     sb600_spibar + 0x00);
			}
		}
		tmp = (mmio_readb(sb600_spibar + 0xd) >> 4) & 0x3;
		msg_pdbg("NormSpeed is %s\n", spispeeds[tmp].name);
	}
	return set_speed(dev, &spispeeds[spispeed_idx]);
}

int sb600_probe_spi(struct pci_dev *dev)
{
	struct pci_dev *smbus_dev;
	uint32_t tmp;
	uint8_t reg;

	/* Read SPI_BaseAddr */
	tmp = pci_read_long(dev, 0xa0);
	tmp &= 0xffffffe0;	/* remove bits 4-0 (reserved) */
	msg_pdbg("SPI base address is at 0x%x\n", tmp);

	/* If the BAR has address 0, it is unlikely SPI is used. */
	if (!tmp)
		return 0;

	/* Physical memory has to be mapped at page (4k) boundaries. */
	sb600_spibar = rphysmap("SB600 SPI registers", tmp & 0xfffff000, 0x1000);
	if (sb600_spibar == ERROR_PTR)
		return ERROR_FATAL;

	/* The low bits of the SPI base address are used as offset into
	 * the mapped page.
	 */
	sb600_spibar += tmp & 0xfff;

	if (determine_generation(dev) < 0)
		return ERROR_NONFATAL;

	/* How to read the following table and similar ones in this file:
	 * "?" means we have no datasheet for this chipset generation or it doesn't have any relevant info.
	 * "<-" means the bit/register meaning is identical to the next non-"?" chipset to the left. "<-" thus
	 *      never refers to another "?".
	 * If a "?" chipset is between two chipsets with identical meaning, we assume the meaning didn't change
	 * twice in between, i.e. the meaning is unchanged for the "?" chipset. Usually we assume that
	 * succeeding hardware supports the same functionality as its predecessor unless proven different by
	 * tests or documentation, hence "?" will often be implemented equally to "<-".
	 *
	 * Chipset support matrix for SPI Base_Addr (LPC PCI reg 0xa0)
	 * bit   6xx         7xx/SP5100       8xx       9xx  hudson1  hudson2+  yangtze
	 * 3    rsvd         <-               <-        ?    <-       ?         RouteTpm2Spi
	 * 2    rsvd         AbortEnable      rsvd      ?    <-       ?         <-
	 * 1    rsvd         SpiRomEnable     <-        ?    <-       ?         <-
	 * 0    rsvd         AltSpiCSEnable   rsvd      ?    <-       ?         <-
	 */
	if (amd_gen >= CHIPSET_SB7XX) {
		tmp = pci_read_long(dev, 0xa0);
		msg_pdbg("SpiRomEnable=%i", (tmp >> 1) & 0x1);
		if (amd_gen == CHIPSET_SB7XX)
			msg_pdbg(", AltSpiCSEnable=%i, AbortEnable=%i", tmp & 0x1, (tmp >> 2) & 0x1);
		else if (amd_gen >= CHIPSET_YANGTZE)
			msg_pdbg(", RouteTpm2Sp=%i", (tmp >> 3) & 0x1);

		tmp = pci_read_byte(dev, 0xba);
		msg_pdbg(", PrefetchEnSPIFromIMC=%i", (tmp & 0x4) >> 2);

		tmp = pci_read_byte(dev, 0xbb);
		/* FIXME: Set bit 3,6,7 if not already set.
		 * Set bit 5, otherwise SPI accesses are pointless in LPC mode.
		 * See doc 42413 AMD SB700/710/750 RPR.
		 */
		if (amd_gen == CHIPSET_SB7XX)
			msg_pdbg(", SpiOpEnInLpcMode=%i", (tmp >> 5) & 0x1);
		msg_pdbg(", PrefetchEnSPIFromHost=%i\n", tmp & 0x1);
	}

	/* Chipset support matrix for SPI_Cntrl0 (spibar + 0x0)
	 * See the chipset support matrix for SPI Base_Addr above for an explanation of the symbols used.
	 * bit   6xx                7xx/SP5100      8xx               9xx  hudson1  hudson2+  yangtze
	 * 17    rsvd               <-              <-                ?    <-       ?         <-
	 * 18    rsvd               <-              fastReadEnable<1> ?    <-       ?         SpiReadMode[0]<1>
	 * 19    SpiArbEnable       <-              <-                ?    <-       ?         <-
	 * 20    (FifoPtrClr)       <-              <-                ?    <-       ?         <-
	 * 21    (FifoPtrInc)       <-              <-                ?    <-       ?         IllegalAccess
	 * 22    SpiAccessMacRomEn  <-              <-                ?    <-       ?         <-
	 * 23    SpiHostAccessRomEn <-              <-                ?    <-       ?         <-
	 * 24:26 ArbWaitCount       <-              <-                ?    <-       ?         <-
	 * 27    SpiBridgeDisable   <-              <-                ?    <-       ?         rsvd
	 * 28    rsvd               DropOneClkOnRd  = SPIClkGate      ?    <-       ?         <-
	 * 29:30 rsvd               <-              <-                ?    <-       ?         SpiReadMode[2:1]<1>
	 * 31    rsvd               <-              SpiBusy           ?    <-       ?         <-
	 *
	 *  <1> see handle_speed
	 */
	tmp = mmio_readl(sb600_spibar + 0x00);
	msg_pdbg("(0x%08" PRIx32 ") SpiArbEnable=%i", tmp, (tmp >> 19) & 0x1);
	if (amd_gen >= CHIPSET_YANGTZE)
		msg_pdbg(", IllegalAccess=%i", (tmp >> 21) & 0x1);

	msg_pdbg(", SpiAccessMacRomEn=%i, SpiHostAccessRomEn=%i, ArbWaitCount=%i",
		 (tmp >> 22) & 0x1, (tmp >> 23) & 0x1, (tmp >> 24) & 0x7);

	if (amd_gen < CHIPSET_YANGTZE)
		msg_pdbg(", SpiBridgeDisable=%i", (tmp >> 27) & 0x1);

	switch (amd_gen) {
	case CHIPSET_SB7XX:
		msg_pdbg(", DropOneClkOnRd/SpiClkGate=%i", (tmp >> 28) & 0x1);
		/* Fall through. */
	case CHIPSET_SB89XX:
	case CHIPSET_HUDSON234:
	case CHIPSET_YANGTZE:
	case CHIPSET_PROMONTORY:
		msg_pdbg(", SpiBusy=%i", (tmp >> 31) & 0x1);
	default: break;
	}
	msg_pdbg("\n");

	if (((tmp >> 22) & 0x1) == 0 || ((tmp >> 23) & 0x1) == 0) {
		msg_perr("ERROR: State of SpiAccessMacRomEn or SpiHostAccessRomEn prohibits full access.\n");
		return ERROR_NONFATAL;
	}

	if (amd_gen >= CHIPSET_SB89XX) {
		tmp = mmio_readb(sb600_spibar + 0x1D);
		msg_pdbg("Using SPI_CS%d\n", tmp & 0x3);
		/* FIXME: Handle SpiProtect* configuration on Yangtze. */
	}

	/* Look for the SMBus device. */
	smbus_dev = pcidev_find(0x1002, 0x4385);
	if (!smbus_dev)
		smbus_dev = pcidev_find(0x1022, 0x780b); /* AMD FCH */
	if (!smbus_dev)
		smbus_dev = pcidev_find(0x1022, 0x790b); /* AMD FP4 */
	if (!smbus_dev) {
		msg_perr("ERROR: SMBus device not found. Not enabling SPI.\n");
		return ERROR_NONFATAL;
	}

	/* Note about the bit tests below: If a bit is zero, the GPIO is SPI. */
	/* GPIO11/SPI_DO and GPIO12/SPI_DI status */
	reg = pci_read_byte(smbus_dev, 0xAB);
	reg &= 0xC0;
	msg_pdbg("GPIO11 used for %s\n", (reg & (1 << 6)) ? "GPIO" : "SPI_DO");
	msg_pdbg("GPIO12 used for %s\n", (reg & (1 << 7)) ? "GPIO" : "SPI_DI");
	if (reg != 0x00) {
		msg_pdbg("Not enabling SPI");
		return 0;
	}
	/* GPIO31/SPI_HOLD and GPIO32/SPI_CS status */
	reg = pci_read_byte(smbus_dev, 0x83);
	reg &= 0xC0;
	msg_pdbg("GPIO31 used for %s\n", (reg & (1 << 6)) ? "GPIO" : "SPI_HOLD");
	msg_pdbg("GPIO32 used for %s\n", (reg & (1 << 7)) ? "GPIO" : "SPI_CS");
	/* SPI_HOLD is not used on all boards, filter it out. */
	if ((reg & 0x80) != 0x00) {
		msg_pdbg("Not enabling SPI");
		return 0;
	}
	/* GPIO47/SPI_CLK status */
	reg = pci_read_byte(smbus_dev, 0xA7);
	reg &= 0x40;
	msg_pdbg("GPIO47 used for %s\n", (reg & (1 << 6)) ? "GPIO" : "SPI_CLK");
	if (reg != 0x00) {
		msg_pdbg("Not enabling SPI");
		return 0;
	}

	if (handle_speed(dev) != 0)
		return ERROR_FATAL;

	/* Handle IMC everywhere but sb600 which does not have one. */
	if (amd_gen != CHIPSET_SB6XX && handle_imc(dev) != 0)
		return ERROR_FATAL;

	/* Starting with Yangtze the SPI controller got a different interface with a much bigger buffer. */
	if (amd_gen < CHIPSET_YANGTZE)
		register_spi_master(&spi_master_sb600, 0, NULL);
	else
		register_spi_master(&spi_master_yangtze, 0, NULL);
	return 0;
}