arch/x86/kernel/amd_nb.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Shared support code for AMD K8 northbridges and derivatives.
  * Copyright 2006 Andi Kleen, SUSE Labs.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/errno.h>
 #include <linux/export.h>
 #include <linux/spinlock.h>
 #include <linux/pci_ids.h>
 #include <asm/amd_nb.h>

 #define PCI_DEVICE_ID_AMD_17H_ROOT		0x1450
 #define PCI_DEVICE_ID_AMD_17H_M10H_ROOT		0x15d0
 #define PCI_DEVICE_ID_AMD_17H_M30H_ROOT		0x1480
 #define PCI_DEVICE_ID_AMD_17H_M60H_ROOT		0x1630
 #define PCI_DEVICE_ID_AMD_17H_MA0H_ROOT		0x14b5
 #define PCI_DEVICE_ID_AMD_19H_M10H_ROOT		0x14a4
 #define PCI_DEVICE_ID_AMD_19H_M40H_ROOT		0x14b5
 #define PCI_DEVICE_ID_AMD_19H_M60H_ROOT		0x14d8
 #define PCI_DEVICE_ID_AMD_19H_M70H_ROOT		0x14e8
 #define PCI_DEVICE_ID_AMD_1AH_M00H_ROOT		0x153a
 #define PCI_DEVICE_ID_AMD_1AH_M20H_ROOT		0x1507
 #define PCI_DEVICE_ID_AMD_MI200_ROOT		0x14bb

 #define PCI_DEVICE_ID_AMD_17H_DF_F4		0x1464
 #define PCI_DEVICE_ID_AMD_17H_M10H_DF_F4	0x15ec
 #define PCI_DEVICE_ID_AMD_17H_M30H_DF_F4	0x1494
 #define PCI_DEVICE_ID_AMD_17H_M60H_DF_F4	0x144c
 #define PCI_DEVICE_ID_AMD_17H_M70H_DF_F4	0x1444
 #define PCI_DEVICE_ID_AMD_17H_MA0H_DF_F4	0x1728
 #define PCI_DEVICE_ID_AMD_19H_DF_F4		0x1654
 #define PCI_DEVICE_ID_AMD_19H_M10H_DF_F4	0x14b1
 #define PCI_DEVICE_ID_AMD_19H_M40H_DF_F4	0x167d
 #define PCI_DEVICE_ID_AMD_19H_M50H_DF_F4	0x166e
 #define PCI_DEVICE_ID_AMD_19H_M60H_DF_F4	0x14e4
 #define PCI_DEVICE_ID_AMD_19H_M70H_DF_F4	0x14f4
 #define PCI_DEVICE_ID_AMD_19H_M78H_DF_F4	0x12fc
 #define PCI_DEVICE_ID_AMD_1AH_M00H_DF_F4	0x12c4
 #define PCI_DEVICE_ID_AMD_MI200_DF_F4		0x14d4

 /* Protect the PCI config register pairs used for SMN. */
 static DEFINE_MUTEX(smn_mutex);

 static u32 *flush_words;

 static const struct pci_device_id amd_root_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M10H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M30H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M60H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_MA0H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M10H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M40H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M60H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M70H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M00H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M20H_ROOT) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_MI200_ROOT) },
 	{}
 };

 #define PCI_DEVICE_ID_AMD_CNB17H_F4     0x1704

 static const struct pci_device_id amd_nb_misc_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_K8_NB_MISC) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_10H_NB_MISC) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_NB_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M10H_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M30H_NB_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M60H_NB_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_NB_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_M30H_NB_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M10H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M30H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M60H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_MA0H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CNB17H_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M70H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M10H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M40H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M50H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M60H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M70H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M78H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M00H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M20H_DF_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_MI200_DF_F3) },
 	{}
 };

 static const struct pci_device_id amd_nb_link_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_NB_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M30H_NB_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M60H_NB_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_NB_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_M30H_NB_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M10H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M30H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M60H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M70H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_MA0H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M10H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M40H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M50H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CNB17H_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M00H_DF_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_MI200_DF_F4) },
 	{}
 };

 static const struct pci_device_id hygon_root_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_HYGON, PCI_DEVICE_ID_AMD_17H_ROOT) },
 	{}
 };

 static const struct pci_device_id hygon_nb_misc_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_HYGON, PCI_DEVICE_ID_AMD_17H_DF_F3) },
 	{}
 };

 static const struct pci_device_id hygon_nb_link_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_HYGON, PCI_DEVICE_ID_AMD_17H_DF_F4) },
 	{}
 };

 const struct amd_nb_bus_dev_range amd_nb_bus_dev_ranges[] __initconst = {
 	{ 0x00, 0x18, 0x20 },
 	{ 0xff, 0x00, 0x20 },
 	{ 0xfe, 0x00, 0x20 },
 	{ }
 };

 static struct amd_northbridge_info amd_northbridges;

 u16 amd_nb_num(void)
 {
 	return amd_northbridges.num;
 }
 EXPORT_SYMBOL_GPL(amd_nb_num);

 bool amd_nb_has_feature(unsigned int feature)
 {
 	return ((amd_northbridges.flags & feature) == feature);
 }
 EXPORT_SYMBOL_GPL(amd_nb_has_feature);

 struct amd_northbridge *node_to_amd_nb(int node)
 {
 	return (node < amd_northbridges.num) ? &amd_northbridges.nb[node] : NULL;
 }
 EXPORT_SYMBOL_GPL(node_to_amd_nb);

 static struct pci_dev *next_northbridge(struct pci_dev *dev,
 					const struct pci_device_id *ids)
 {
 	do {
 		dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev);
 		if (!dev)
 			break;
 	} while (!pci_match_id(ids, dev));
 	return dev;
 }

 static int __amd_smn_rw(u16 node, u32 address, u32 *value, bool write)
 {
 	struct pci_dev *root;
 	int err = -ENODEV;

 	if (node >= amd_northbridges.num)
 		goto out;

 	root = node_to_amd_nb(node)->root;
 	if (!root)
 		goto out;

 	mutex_lock(&smn_mutex);

 	err = pci_write_config_dword(root, 0x60, address);
 	if (err) {
 		pr_warn("Error programming SMN address 0x%x.\n", address);
 		goto out_unlock;
 	}

 	err = (write ? pci_write_config_dword(root, 0x64, *value)
 		     : pci_read_config_dword(root, 0x64, value));
 	if (err)
 		pr_warn("Error %s SMN address 0x%x.\n",
 			(write ? "writing to" : "reading from"), address);

 out_unlock:
 	mutex_unlock(&smn_mutex);

 out:
 	return err;
 }

 int amd_smn_read(u16 node, u32 address, u32 *value)
 {
 	return __amd_smn_rw(node, address, value, false);
 }
 EXPORT_SYMBOL_GPL(amd_smn_read);

 int amd_smn_write(u16 node, u32 address, u32 value)
 {
 	return __amd_smn_rw(node, address, &value, true);
 }
 EXPORT_SYMBOL_GPL(amd_smn_write);


 static int amd_cache_northbridges(void)
 {
 	const struct pci_device_id *misc_ids = amd_nb_misc_ids;
 	const struct pci_device_id *link_ids = amd_nb_link_ids;
 	const struct pci_device_id *root_ids = amd_root_ids;
 	struct pci_dev *root, *misc, *link;
 	struct amd_northbridge *nb;
 	u16 roots_per_misc = 0;
 	u16 misc_count = 0;
 	u16 root_count = 0;
 	u16 i, j;

 	if (amd_northbridges.num)
 		return 0;

 	if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 		root_ids = hygon_root_ids;
 		misc_ids = hygon_nb_misc_ids;
 		link_ids = hygon_nb_link_ids;
 	}

 	misc = NULL;
 	while ((misc = next_northbridge(misc, misc_ids)))
 		misc_count++;

 	if (!misc_count)
 		return -ENODEV;

 	root = NULL;
 	while ((root = next_northbridge(root, root_ids)))
 		root_count++;

 	if (root_count) {
 		roots_per_misc = root_count / misc_count;

 		/*
 		 * There should be _exactly_ N roots for each DF/SMN
 		 * interface.
 		 */
 		if (!roots_per_misc || (root_count % roots_per_misc)) {
 			pr_info("Unsupported AMD DF/PCI configuration found\n");
 			return -ENODEV;
 		}
 	}

 	nb = kcalloc(misc_count, sizeof(struct amd_northbridge), GFP_KERNEL);
 	if (!nb)
 		return -ENOMEM;

 	amd_northbridges.nb = nb;
 	amd_northbridges.num = misc_count;

 	link = misc = root = NULL;
 	for (i = 0; i < amd_northbridges.num; i++) {
 		node_to_amd_nb(i)->root = root =
 			next_northbridge(root, root_ids);
 		node_to_amd_nb(i)->misc = misc =
 			next_northbridge(misc, misc_ids);
 		node_to_amd_nb(i)->link = link =
 			next_northbridge(link, link_ids);

 		/*
 		 * If there are more PCI root devices than data fabric/
 		 * system management network interfaces, then the (N)
 		 * PCI roots per DF/SMN interface are functionally the
 		 * same (for DF/SMN access) and N-1 are redundant.  N-1
 		 * PCI roots should be skipped per DF/SMN interface so
 		 * the following DF/SMN interfaces get mapped to
 		 * correct PCI roots.
 		 */
 		for (j = 1; j < roots_per_misc; j++)
 			root = next_northbridge(root, root_ids);
 	}

 	if (amd_gart_present())
 		amd_northbridges.flags |= AMD_NB_GART;

 	/*
 	 * Check for L3 cache presence.
 	 */
 	if (!cpuid_edx(0x80000006))
 		return 0;

 	/*
 	 * Some CPU families support L3 Cache Index Disable. There are some
 	 * limitations because of E382 and E388 on family 0x10.
 	 */
 	if (boot_cpu_data.x86 == 0x10 &&
 	    boot_cpu_data.x86_model >= 0x8 &&
 	    (boot_cpu_data.x86_model > 0x9 ||
 	     boot_cpu_data.x86_stepping >= 0x1))
 		amd_northbridges.flags |= AMD_NB_L3_INDEX_DISABLE;

 	if (boot_cpu_data.x86 == 0x15)
 		amd_northbridges.flags |= AMD_NB_L3_INDEX_DISABLE;

 	/* L3 cache partitioning is supported on family 0x15 */
 	if (boot_cpu_data.x86 == 0x15)
 		amd_northbridges.flags |= AMD_NB_L3_PARTITIONING;

 	return 0;
 }

 /*
  * Ignores subdevice/subvendor but as far as I can figure out
  * they're useless anyways
  */
 bool __init early_is_amd_nb(u32 device)
 {
 	const struct pci_device_id *misc_ids = amd_nb_misc_ids;
 	const struct pci_device_id *id;
 	u32 vendor = device & 0xffff;

 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
 		return false;

 	if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
 		misc_ids = hygon_nb_misc_ids;

 	device >>= 16;
 	for (id = misc_ids; id->vendor; id++)
 		if (vendor == id->vendor && device == id->device)
 			return true;
 	return false;
 }

 struct resource *amd_get_mmconfig_range(struct resource *res)
 {
 	u32 address;
 	u64 base, msr;
 	unsigned int segn_busn_bits;

 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
 		return NULL;

 	/* assume all cpus from fam10h have mmconfig */
 	if (boot_cpu_data.x86 < 0x10)
 		return NULL;

 	address = MSR_FAM10H_MMIO_CONF_BASE;
 	rdmsrl(address, msr);

 	/* mmconfig is not enabled */
 	if (!(msr & FAM10H_MMIO_CONF_ENABLE))
 		return NULL;

 	base = msr & (FAM10H_MMIO_CONF_BASE_MASK<<FAM10H_MMIO_CONF_BASE_SHIFT);

 	segn_busn_bits = (msr >> FAM10H_MMIO_CONF_BUSRANGE_SHIFT) &
 			 FAM10H_MMIO_CONF_BUSRANGE_MASK;

 	res->flags = IORESOURCE_MEM;
 	res->start = base;
 	res->end = base + (1ULL<<(segn_busn_bits + 20)) - 1;
 	return res;
 }

 int amd_get_subcaches(int cpu)
 {
 	struct pci_dev *link = node_to_amd_nb(topology_die_id(cpu))->link;
 	unsigned int mask;

 	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING))
 		return 0;

 	pci_read_config_dword(link, 0x1d4, &mask);

 	return (mask >> (4 * cpu_data(cpu).cpu_core_id)) & 0xf;
 }

 int amd_set_subcaches(int cpu, unsigned long mask)
 {
 	static unsigned int reset, ban;
 	struct amd_northbridge *nb = node_to_amd_nb(topology_die_id(cpu));
 	unsigned int reg;
 	int cuid;

 	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING) || mask > 0xf)
 		return -EINVAL;

 	/* if necessary, collect reset state of L3 partitioning and BAN mode */
 	if (reset == 0) {
 		pci_read_config_dword(nb->link, 0x1d4, &reset);
 		pci_read_config_dword(nb->misc, 0x1b8, &ban);
 		ban &= 0x180000;
 	}

 	/* deactivate BAN mode if any subcaches are to be disabled */
 	if (mask != 0xf) {
 		pci_read_config_dword(nb->misc, 0x1b8, &reg);
 		pci_write_config_dword(nb->misc, 0x1b8, reg & ~0x180000);
 	}

 	cuid = cpu_data(cpu).cpu_core_id;
 	mask <<= 4 * cuid;
 	mask |= (0xf ^ (1 << cuid)) << 26;

 	pci_write_config_dword(nb->link, 0x1d4, mask);

 	/* reset BAN mode if L3 partitioning returned to reset state */
 	pci_read_config_dword(nb->link, 0x1d4, &reg);
 	if (reg == reset) {
 		pci_read_config_dword(nb->misc, 0x1b8, &reg);
 		reg &= ~0x180000;
 		pci_write_config_dword(nb->misc, 0x1b8, reg | ban);
 	}

 	return 0;
 }

 static void amd_cache_gart(void)
 {
 	u16 i;

 	if (!amd_nb_has_feature(AMD_NB_GART))
 		return;

 	flush_words = kmalloc_array(amd_northbridges.num, sizeof(u32), GFP_KERNEL);
 	if (!flush_words) {
 		amd_northbridges.flags &= ~AMD_NB_GART;
 		pr_notice("Cannot initialize GART flush words, GART support disabled\n");
 		return;
 	}

 	for (i = 0; i != amd_northbridges.num; i++)
 		pci_read_config_dword(node_to_amd_nb(i)->misc, 0x9c, &flush_words[i]);
 }

 void amd_flush_garts(void)
 {
 	int flushed, i;
 	unsigned long flags;
 	static DEFINE_SPINLOCK(gart_lock);

 	if (!amd_nb_has_feature(AMD_NB_GART))
 		return;

 	/*
 	 * Avoid races between AGP and IOMMU. In theory it's not needed
 	 * but I'm not sure if the hardware won't lose flush requests
 	 * when another is pending. This whole thing is so expensive anyways
 	 * that it doesn't matter to serialize more. -AK
 	 */
 	spin_lock_irqsave(&gart_lock, flags);
 	flushed = 0;
 	for (i = 0; i < amd_northbridges.num; i++) {
 		pci_write_config_dword(node_to_amd_nb(i)->misc, 0x9c,
 				       flush_words[i] | 1);
 		flushed++;
 	}
 	for (i = 0; i < amd_northbridges.num; i++) {
 		u32 w;
 		/* Make sure the hardware actually executed the flush*/
 		for (;;) {
 			pci_read_config_dword(node_to_amd_nb(i)->misc,
 					      0x9c, &w);
 			if (!(w & 1))
 				break;
 			cpu_relax();
 		}
 	}
 	spin_unlock_irqrestore(&gart_lock, flags);
 	if (!flushed)
 		pr_notice("nothing to flush?\n");
 }
 EXPORT_SYMBOL_GPL(amd_flush_garts);

 static void __fix_erratum_688(void *info)
 {
 #define MSR_AMD64_IC_CFG 0xC0011021

 	msr_set_bit(MSR_AMD64_IC_CFG, 3);
 	msr_set_bit(MSR_AMD64_IC_CFG, 14);
 }

 /* Apply erratum 688 fix so machines without a BIOS fix work. */
 static __init void fix_erratum_688(void)
 {
 	struct pci_dev *F4;
 	u32 val;

 	if (boot_cpu_data.x86 != 0x14)
 		return;

 	if (!amd_northbridges.num)
 		return;

 	F4 = node_to_amd_nb(0)->link;
 	if (!F4)
 		return;

 	if (pci_read_config_dword(F4, 0x164, &val))
 		return;

 	if (val & BIT(2))
 		return;

 	on_each_cpu(__fix_erratum_688, NULL, 0);

 	pr_info("x86/cpu/AMD: CPU erratum 688 worked around\n");
 }

 static __init int init_amd_nbs(void)
 {
 	amd_cache_northbridges();
 	amd_cache_gart();

 	fix_erratum_688();

 	return 0;
 }

 /* This has to go after the PCI subsystem */
 fs_initcall(init_amd_nbs);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Shared support code for AMD K8 northbridges and derivatives.
	* Copyright 2006 Andi Kleen, SUSE Labs.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/types.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <linux/errno.h>
	#include <linux/export.h>
	#include <linux/spinlock.h>
	#include <linux/pci_ids.h>
	#include <asm/amd_nb.h>

	#define PCI_DEVICE_ID_AMD_17H_ROOT 0x1450
	#define PCI_DEVICE_ID_AMD_17H_M10H_ROOT 0x15d0
	#define PCI_DEVICE_ID_AMD_17H_M30H_ROOT 0x1480
	#define PCI_DEVICE_ID_AMD_17H_M60H_ROOT 0x1630
	#define PCI_DEVICE_ID_AMD_17H_MA0H_ROOT 0x14b5
	#define PCI_DEVICE_ID_AMD_19H_M10H_ROOT 0x14a4
	#define PCI_DEVICE_ID_AMD_19H_M40H_ROOT 0x14b5
	#define PCI_DEVICE_ID_AMD_19H_M60H_ROOT 0x14d8
	#define PCI_DEVICE_ID_AMD_19H_M70H_ROOT 0x14e8
	#define PCI_DEVICE_ID_AMD_1AH_M00H_ROOT 0x153a
	#define PCI_DEVICE_ID_AMD_1AH_M20H_ROOT 0x1507
	#define PCI_DEVICE_ID_AMD_MI200_ROOT 0x14bb

	#define PCI_DEVICE_ID_AMD_17H_DF_F4 0x1464
	#define PCI_DEVICE_ID_AMD_17H_M10H_DF_F4 0x15ec
	#define PCI_DEVICE_ID_AMD_17H_M30H_DF_F4 0x1494
	#define PCI_DEVICE_ID_AMD_17H_M60H_DF_F4 0x144c
	#define PCI_DEVICE_ID_AMD_17H_M70H_DF_F4 0x1444
	#define PCI_DEVICE_ID_AMD_17H_MA0H_DF_F4 0x1728
	#define PCI_DEVICE_ID_AMD_19H_DF_F4 0x1654
	#define PCI_DEVICE_ID_AMD_19H_M10H_DF_F4 0x14b1
	#define PCI_DEVICE_ID_AMD_19H_M40H_DF_F4 0x167d
	#define PCI_DEVICE_ID_AMD_19H_M50H_DF_F4 0x166e
	#define PCI_DEVICE_ID_AMD_19H_M60H_DF_F4 0x14e4
	#define PCI_DEVICE_ID_AMD_19H_M70H_DF_F4 0x14f4
	#define PCI_DEVICE_ID_AMD_19H_M78H_DF_F4 0x12fc
	#define PCI_DEVICE_ID_AMD_1AH_M00H_DF_F4 0x12c4
	#define PCI_DEVICE_ID_AMD_MI200_DF_F4 0x14d4

	/* Protect the PCI config register pairs used for SMN. */
	static DEFINE_MUTEX(smn_mutex);

	static u32 *flush_words;

	static const struct pci_device_id amd_root_ids[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M10H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M30H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M60H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_MA0H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M10H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M40H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M60H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M70H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M00H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M20H_ROOT) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_MI200_ROOT) },
	{}
	};

	#define PCI_DEVICE_ID_AMD_CNB17H_F4 0x1704

	static const struct pci_device_id amd_nb_misc_ids[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_K8_NB_MISC) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_10H_NB_MISC) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_NB_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M10H_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M30H_NB_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M60H_NB_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_NB_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_M30H_NB_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M10H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M30H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M60H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_MA0H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CNB17H_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M70H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M10H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M40H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M50H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M60H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M70H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M78H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M00H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M20H_DF_F3) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_MI200_DF_F3) },
	{}
	};

	static const struct pci_device_id amd_nb_link_ids[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_NB_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M30H_NB_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M60H_NB_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_NB_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_M30H_NB_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M10H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M30H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M60H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_M70H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_17H_MA0H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M10H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M40H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_19H_M50H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CNB17H_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_1AH_M00H_DF_F4) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_MI200_DF_F4) },
	{}
	};

	static const struct pci_device_id hygon_root_ids[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_HYGON, PCI_DEVICE_ID_AMD_17H_ROOT) },
	{}
	};

	static const struct pci_device_id hygon_nb_misc_ids[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_HYGON, PCI_DEVICE_ID_AMD_17H_DF_F3) },
	{}
	};

	static const struct pci_device_id hygon_nb_link_ids[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_HYGON, PCI_DEVICE_ID_AMD_17H_DF_F4) },
	{}
	};

	const struct amd_nb_bus_dev_range amd_nb_bus_dev_ranges[] __initconst = {
	{ 0x00, 0x18, 0x20 },
	{ 0xff, 0x00, 0x20 },
	{ 0xfe, 0x00, 0x20 },
	{ }
	};

	static struct amd_northbridge_info amd_northbridges;

	u16 amd_nb_num(void)
	{
	return amd_northbridges.num;
	}
	EXPORT_SYMBOL_GPL(amd_nb_num);

	bool amd_nb_has_feature(unsigned int feature)
	{
	return ((amd_northbridges.flags & feature) == feature);
	}
	EXPORT_SYMBOL_GPL(amd_nb_has_feature);

	struct amd_northbridge *node_to_amd_nb(int node)
	{
	return (node < amd_northbridges.num) ? &amd_northbridges.nb[node] : NULL;
	}
	EXPORT_SYMBOL_GPL(node_to_amd_nb);

	static struct pci_dev next_northbridge(struct pci_dev dev,
	const struct pci_device_id *ids)
	{
	do {
	dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev);
	if (!dev)
	break;
	} while (!pci_match_id(ids, dev));
	return dev;
	}

	static int __amd_smn_rw(u16 node, u32 address, u32 *value, bool write)
	{
	struct pci_dev *root;
	int err = -ENODEV;

	if (node >= amd_northbridges.num)
	goto out;

	root = node_to_amd_nb(node)->root;
	if (!root)
	goto out;

	mutex_lock(&smn_mutex);

	err = pci_write_config_dword(root, 0x60, address);
	if (err) {
	pr_warn("Error programming SMN address 0x%x.\n", address);
	goto out_unlock;
	}

	err = (write ? pci_write_config_dword(root, 0x64, *value)
	: pci_read_config_dword(root, 0x64, value));
	if (err)
	pr_warn("Error %s SMN address 0x%x.\n",
	(write ? "writing to" : "reading from"), address);

	out_unlock:
	mutex_unlock(&smn_mutex);

	out:
	return err;
	}

	int amd_smn_read(u16 node, u32 address, u32 *value)
	{
	return __amd_smn_rw(node, address, value, false);
	}
	EXPORT_SYMBOL_GPL(amd_smn_read);

	int amd_smn_write(u16 node, u32 address, u32 value)
	{
	return __amd_smn_rw(node, address, &value, true);
	}
	EXPORT_SYMBOL_GPL(amd_smn_write);


	static int amd_cache_northbridges(void)
	{
	const struct pci_device_id *misc_ids = amd_nb_misc_ids;
	const struct pci_device_id *link_ids = amd_nb_link_ids;
	const struct pci_device_id *root_ids = amd_root_ids;
	struct pci_dev root, misc, *link;
	struct amd_northbridge *nb;
	u16 roots_per_misc = 0;
	u16 misc_count = 0;
	u16 root_count = 0;
	u16 i, j;

	if (amd_northbridges.num)
	return 0;

	if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
	root_ids = hygon_root_ids;
	misc_ids = hygon_nb_misc_ids;
	link_ids = hygon_nb_link_ids;
	}

	misc = NULL;
	while ((misc = next_northbridge(misc, misc_ids)))
	misc_count++;

	if (!misc_count)
	return -ENODEV;

	root = NULL;
	while ((root = next_northbridge(root, root_ids)))
	root_count++;

	if (root_count) {
	roots_per_misc = root_count / misc_count;

	/*
	* There should be _exactly_ N roots for each DF/SMN
	* interface.
	*/
	if (!roots_per_misc \|\| (root_count % roots_per_misc)) {
	pr_info("Unsupported AMD DF/PCI configuration found\n");
	return -ENODEV;
	}
	}

	nb = kcalloc(misc_count, sizeof(struct amd_northbridge), GFP_KERNEL);
	if (!nb)
	return -ENOMEM;

	amd_northbridges.nb = nb;
	amd_northbridges.num = misc_count;

	link = misc = root = NULL;
	for (i = 0; i < amd_northbridges.num; i++) {
	node_to_amd_nb(i)->root = root =
	next_northbridge(root, root_ids);
	node_to_amd_nb(i)->misc = misc =
	next_northbridge(misc, misc_ids);
	node_to_amd_nb(i)->link = link =
	next_northbridge(link, link_ids);

	/*
	* If there are more PCI root devices than data fabric/
	* system management network interfaces, then the (N)
	* PCI roots per DF/SMN interface are functionally the
	* same (for DF/SMN access) and N-1 are redundant. N-1
	* PCI roots should be skipped per DF/SMN interface so
	* the following DF/SMN interfaces get mapped to
	* correct PCI roots.
	*/
	for (j = 1; j < roots_per_misc; j++)
	root = next_northbridge(root, root_ids);
	}

	if (amd_gart_present())
	amd_northbridges.flags \|= AMD_NB_GART;

	/*
	* Check for L3 cache presence.
	*/
	if (!cpuid_edx(0x80000006))
	return 0;

	/*
	* Some CPU families support L3 Cache Index Disable. There are some
	* limitations because of E382 and E388 on family 0x10.
	*/
	if (boot_cpu_data.x86 == 0x10 &&
	boot_cpu_data.x86_model >= 0x8 &&
	(boot_cpu_data.x86_model > 0x9 \|\|
	boot_cpu_data.x86_stepping >= 0x1))
	amd_northbridges.flags \|= AMD_NB_L3_INDEX_DISABLE;

	if (boot_cpu_data.x86 == 0x15)
	amd_northbridges.flags \|= AMD_NB_L3_INDEX_DISABLE;

	/* L3 cache partitioning is supported on family 0x15 */
	if (boot_cpu_data.x86 == 0x15)
	amd_northbridges.flags \|= AMD_NB_L3_PARTITIONING;

	return 0;
	}

	/*
	* Ignores subdevice/subvendor but as far as I can figure out
	* they're useless anyways
	*/
	bool __init early_is_amd_nb(u32 device)
	{
	const struct pci_device_id *misc_ids = amd_nb_misc_ids;
	const struct pci_device_id *id;
	u32 vendor = device & 0xffff;

	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
	boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
	return false;

	if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
	misc_ids = hygon_nb_misc_ids;

	device >>= 16;
	for (id = misc_ids; id->vendor; id++)
	if (vendor == id->vendor && device == id->device)
	return true;
	return false;
	}

	struct resource amd_get_mmconfig_range(struct resource res)
	{
	u32 address;
	u64 base, msr;
	unsigned int segn_busn_bits;

	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
	boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
	return NULL;

	/* assume all cpus from fam10h have mmconfig */
	if (boot_cpu_data.x86 < 0x10)
	return NULL;

	address = MSR_FAM10H_MMIO_CONF_BASE;
	rdmsrl(address, msr);

	/* mmconfig is not enabled */
	if (!(msr & FAM10H_MMIO_CONF_ENABLE))
	return NULL;

	base = msr & (FAM10H_MMIO_CONF_BASE_MASK<<FAM10H_MMIO_CONF_BASE_SHIFT);

	segn_busn_bits = (msr >> FAM10H_MMIO_CONF_BUSRANGE_SHIFT) &
	FAM10H_MMIO_CONF_BUSRANGE_MASK;

	res->flags = IORESOURCE_MEM;
	res->start = base;
	res->end = base + (1ULL<<(segn_busn_bits + 20)) - 1;
	return res;
	}

	int amd_get_subcaches(int cpu)
	{
	struct pci_dev *link = node_to_amd_nb(topology_die_id(cpu))->link;
	unsigned int mask;

	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING))
	return 0;

	pci_read_config_dword(link, 0x1d4, &mask);

	return (mask >> (4 * cpu_data(cpu).cpu_core_id)) & 0xf;
	}

	int amd_set_subcaches(int cpu, unsigned long mask)
	{
	static unsigned int reset, ban;
	struct amd_northbridge *nb = node_to_amd_nb(topology_die_id(cpu));
	unsigned int reg;
	int cuid;

	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING) \|\| mask > 0xf)
	return -EINVAL;

	/* if necessary, collect reset state of L3 partitioning and BAN mode */
	if (reset == 0) {
	pci_read_config_dword(nb->link, 0x1d4, &reset);
	pci_read_config_dword(nb->misc, 0x1b8, &ban);
	ban &= 0x180000;
	}

	/* deactivate BAN mode if any subcaches are to be disabled */
	if (mask != 0xf) {
	pci_read_config_dword(nb->misc, 0x1b8, &reg);
	pci_write_config_dword(nb->misc, 0x1b8, reg & ~0x180000);
	}

	cuid = cpu_data(cpu).cpu_core_id;
	mask <<= 4 * cuid;
	mask \|= (0xf ^ (1 << cuid)) << 26;

	pci_write_config_dword(nb->link, 0x1d4, mask);

	/* reset BAN mode if L3 partitioning returned to reset state */
	pci_read_config_dword(nb->link, 0x1d4, &reg);
	if (reg == reset) {
	pci_read_config_dword(nb->misc, 0x1b8, &reg);
	reg &= ~0x180000;
	pci_write_config_dword(nb->misc, 0x1b8, reg \| ban);
	}

	return 0;
	}

	static void amd_cache_gart(void)
	{
	u16 i;

	if (!amd_nb_has_feature(AMD_NB_GART))
	return;

	flush_words = kmalloc_array(amd_northbridges.num, sizeof(u32), GFP_KERNEL);
	if (!flush_words) {
	amd_northbridges.flags &= ~AMD_NB_GART;
	pr_notice("Cannot initialize GART flush words, GART support disabled\n");
	return;
	}

	for (i = 0; i != amd_northbridges.num; i++)
	pci_read_config_dword(node_to_amd_nb(i)->misc, 0x9c, &flush_words[i]);
	}

	void amd_flush_garts(void)
	{
	int flushed, i;
	unsigned long flags;
	static DEFINE_SPINLOCK(gart_lock);

	if (!amd_nb_has_feature(AMD_NB_GART))
	return;

	/*
	* Avoid races between AGP and IOMMU. In theory it's not needed
	* but I'm not sure if the hardware won't lose flush requests
	* when another is pending. This whole thing is so expensive anyways
	* that it doesn't matter to serialize more. -AK
	*/
	spin_lock_irqsave(&gart_lock, flags);
	flushed = 0;
	for (i = 0; i < amd_northbridges.num; i++) {
	pci_write_config_dword(node_to_amd_nb(i)->misc, 0x9c,
	flush_words[i] \| 1);
	flushed++;
	}
	for (i = 0; i < amd_northbridges.num; i++) {
	u32 w;
	/* Make sure the hardware actually executed the flush*/
	for (;;) {
	pci_read_config_dword(node_to_amd_nb(i)->misc,
	0x9c, &w);
	if (!(w & 1))
	break;
	cpu_relax();
	}
	}
	spin_unlock_irqrestore(&gart_lock, flags);
	if (!flushed)
	pr_notice("nothing to flush?\n");
	}
	EXPORT_SYMBOL_GPL(amd_flush_garts);

	static void __fix_erratum_688(void *info)
	{
	#define MSR_AMD64_IC_CFG 0xC0011021

	msr_set_bit(MSR_AMD64_IC_CFG, 3);
	msr_set_bit(MSR_AMD64_IC_CFG, 14);
	}

	/* Apply erratum 688 fix so machines without a BIOS fix work. */
	static __init void fix_erratum_688(void)
	{
	struct pci_dev *F4;
	u32 val;

	if (boot_cpu_data.x86 != 0x14)
	return;

	if (!amd_northbridges.num)
	return;

	F4 = node_to_amd_nb(0)->link;
	if (!F4)
	return;

	if (pci_read_config_dword(F4, 0x164, &val))
	return;

	if (val & BIT(2))
	return;

	on_each_cpu(__fix_erratum_688, NULL, 0);

	pr_info("x86/cpu/AMD: CPU erratum 688 worked around\n");
	}

	static __init int init_amd_nbs(void)
	{
	amd_cache_northbridges();
	amd_cache_gart();

	fix_erratum_688();

	return 0;
	}

	/* This has to go after the PCI subsystem */
	fs_initcall(init_amd_nbs);