drivers/dma/ioat/dca.c - kernel/bruno - Git at Google

 /*
  * Intel I/OAT DMA Linux driver
  * Copyright(c) 2007 - 2009 Intel Corporation.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms and conditions of the GNU General Public License,
  * version 2, as published by the Free Software Foundation.
  *
  * 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.
  *
  * The full GNU General Public License is included in this distribution in
  * the file called "COPYING".
  *
  */

 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/smp.h>
 #include <linux/interrupt.h>
 #include <linux/dca.h>

 /* either a kernel change is needed, or we need something like this in kernel */
 #ifndef CONFIG_SMP
 #include <asm/smp.h>
 #undef cpu_physical_id
 #define cpu_physical_id(cpu) (cpuid_ebx(1) >> 24)
 #endif

 #include "dma.h"
 #include "registers.h"

 /*
  * Bit 7 of a tag map entry is the "valid" bit, if it is set then bits 0:6
  * contain the bit number of the APIC ID to map into the DCA tag.  If the valid
  * bit is not set, then the value must be 0 or 1 and defines the bit in the tag.
  */
 #define DCA_TAG_MAP_VALID 0x80

 #define DCA3_TAG_MAP_BIT_TO_INV 0x80
 #define DCA3_TAG_MAP_BIT_TO_SEL 0x40
 #define DCA3_TAG_MAP_LITERAL_VAL 0x1

 #define DCA_TAG_MAP_MASK 0xDF

 /* expected tag map bytes for I/OAT ver.2 */
 #define DCA2_TAG_MAP_BYTE0 0x80
 #define DCA2_TAG_MAP_BYTE1 0x0
 #define DCA2_TAG_MAP_BYTE2 0x81
 #define DCA2_TAG_MAP_BYTE3 0x82
 #define DCA2_TAG_MAP_BYTE4 0x82

 /* verify if tag map matches expected values */
 static inline int dca2_tag_map_valid(u8 *tag_map)
 {
 	return ((tag_map[0] == DCA2_TAG_MAP_BYTE0) &&
 		(tag_map[1] == DCA2_TAG_MAP_BYTE1) &&
 		(tag_map[2] == DCA2_TAG_MAP_BYTE2) &&
 		(tag_map[3] == DCA2_TAG_MAP_BYTE3) &&
 		(tag_map[4] == DCA2_TAG_MAP_BYTE4));
 }

 /*
  * "Legacy" DCA systems do not implement the DCA register set in the
  * I/OAT device.  Software needs direct support for their tag mappings.
  */

 #define APICID_BIT(x)		(DCA_TAG_MAP_VALID | (x))
 #define IOAT_TAG_MAP_LEN	8

 /* pack PCI B/D/F into a u16 */
 static inline u16 dcaid_from_pcidev(struct pci_dev *pci)
 {
 	return (pci->bus->number << 8) | pci->devfn;
 }

 static int dca_enabled_in_bios(struct pci_dev *pdev)
 {
 	/* CPUID level 9 returns DCA configuration */
 	/* Bit 0 indicates DCA enabled by the BIOS */
 	unsigned long cpuid_level_9;
 	int res;

 	cpuid_level_9 = cpuid_eax(9);
 	res = test_bit(0, &cpuid_level_9);
 	if (!res)
 		dev_dbg(&pdev->dev, "DCA is disabled in BIOS\n");

 	return res;
 }

 int system_has_dca_enabled(struct pci_dev *pdev)
 {
 	if (boot_cpu_has(X86_FEATURE_DCA))
 		return dca_enabled_in_bios(pdev);

 	dev_dbg(&pdev->dev, "boot cpu doesn't have X86_FEATURE_DCA\n");
 	return 0;
 }

 struct ioat_dca_slot {
 	struct pci_dev *pdev;	/* requester device */
 	u16 rid;		/* requester id, as used by IOAT */
 };

 #define IOAT_DCA_MAX_REQ 6
 #define IOAT3_DCA_MAX_REQ 2

 struct ioat_dca_priv {
 	void __iomem		*iobase;
 	void __iomem		*dca_base;
 	int			 max_requesters;
 	int			 requester_count;
 	u8			 tag_map[IOAT_TAG_MAP_LEN];
 	struct ioat_dca_slot 	 req_slots[0];
 };

 static int ioat_dca_dev_managed(struct dca_provider *dca,
 				struct device *dev)
 {
 	struct ioat_dca_priv *ioatdca = dca_priv(dca);
 	struct pci_dev *pdev;
 	int i;

 	pdev = to_pci_dev(dev);
 	for (i = 0; i < ioatdca->max_requesters; i++) {
 		if (ioatdca->req_slots[i].pdev == pdev)
 			return 1;
 	}
 	return 0;
 }

 static int ioat_dca_add_requester(struct dca_provider *dca, struct device *dev)
 {
 	struct ioat_dca_priv *ioatdca = dca_priv(dca);
 	struct pci_dev *pdev;
 	int i;
 	u16 id;
 	u16 global_req_table;

 	/* This implementation only supports PCI-Express */
 	if (!dev_is_pci(dev))
 		return -ENODEV;
 	pdev = to_pci_dev(dev);
 	id = dcaid_from_pcidev(pdev);

 	if (ioatdca->requester_count == ioatdca->max_requesters)
 		return -ENODEV;

 	for (i = 0; i < ioatdca->max_requesters; i++) {
 		if (ioatdca->req_slots[i].pdev == NULL) {
 			/* found an empty slot */
 			ioatdca->requester_count++;
 			ioatdca->req_slots[i].pdev = pdev;
 			ioatdca->req_slots[i].rid = id;
 			global_req_table =
 			      readw(ioatdca->dca_base + IOAT3_DCA_GREQID_OFFSET);
 			writel(id | IOAT_DCA_GREQID_VALID,
 			       ioatdca->iobase + global_req_table + (i * 4));
 			return i;
 		}
 	}
 	/* Error, ioatdma->requester_count is out of whack */
 	return -EFAULT;
 }

 static int ioat_dca_remove_requester(struct dca_provider *dca,
 				      struct device *dev)
 {
 	struct ioat_dca_priv *ioatdca = dca_priv(dca);
 	struct pci_dev *pdev;
 	int i;
 	u16 global_req_table;

 	/* This implementation only supports PCI-Express */
 	if (!dev_is_pci(dev))
 		return -ENODEV;
 	pdev = to_pci_dev(dev);

 	for (i = 0; i < ioatdca->max_requesters; i++) {
 		if (ioatdca->req_slots[i].pdev == pdev) {
 			global_req_table =
 			      readw(ioatdca->dca_base + IOAT3_DCA_GREQID_OFFSET);
 			writel(0, ioatdca->iobase + global_req_table + (i * 4));
 			ioatdca->req_slots[i].pdev = NULL;
 			ioatdca->req_slots[i].rid = 0;
 			ioatdca->requester_count--;
 			return i;
 		}
 	}
 	return -ENODEV;
 }

 static u8 ioat_dca_get_tag(struct dca_provider *dca,
 			    struct device *dev,
 			    int cpu)
 {
 	u8 tag;

 	struct ioat_dca_priv *ioatdca = dca_priv(dca);
 	int i, apic_id, bit, value;
 	u8 entry;

 	tag = 0;
 	apic_id = cpu_physical_id(cpu);

 	for (i = 0; i < IOAT_TAG_MAP_LEN; i++) {
 		entry = ioatdca->tag_map[i];
 		if (entry & DCA3_TAG_MAP_BIT_TO_SEL) {
 			bit = entry &
 				~(DCA3_TAG_MAP_BIT_TO_SEL | DCA3_TAG_MAP_BIT_TO_INV);
 			value = (apic_id & (1 << bit)) ? 1 : 0;
 		} else if (entry & DCA3_TAG_MAP_BIT_TO_INV) {
 			bit = entry & ~DCA3_TAG_MAP_BIT_TO_INV;
 			value = (apic_id & (1 << bit)) ? 0 : 1;
 		} else {
 			value = (entry & DCA3_TAG_MAP_LITERAL_VAL) ? 1 : 0;
 		}
 		tag |= (value << i);
 	}

 	return tag;
 }

 static struct dca_ops ioat_dca_ops = {
 	.add_requester		= ioat_dca_add_requester,
 	.remove_requester	= ioat_dca_remove_requester,
 	.get_tag		= ioat_dca_get_tag,
 	.dev_managed		= ioat_dca_dev_managed,
 };

 static int ioat_dca_count_dca_slots(void *iobase, u16 dca_offset)
 {
 	int slots = 0;
 	u32 req;
 	u16 global_req_table;

 	global_req_table = readw(iobase + dca_offset + IOAT3_DCA_GREQID_OFFSET);
 	if (global_req_table == 0)
 		return 0;

 	do {
 		req = readl(iobase + global_req_table + (slots * sizeof(u32)));
 		slots++;
 	} while ((req & IOAT_DCA_GREQID_LASTID) == 0);

 	return slots;
 }

 static inline int dca3_tag_map_invalid(u8 *tag_map)
 {
 	/*
 	 * If the tag map is not programmed by the BIOS the default is:
 	 * 0x80 0x80 0x80 0x80 0x80 0x00 0x00 0x00
 	 *
 	 * This an invalid map and will result in only 2 possible tags
 	 * 0x1F and 0x00.  0x00 is an invalid DCA tag so we know that
 	 * this entire definition is invalid.
 	 */
 	return ((tag_map[0] == DCA_TAG_MAP_VALID) &&
 		(tag_map[1] == DCA_TAG_MAP_VALID) &&
 		(tag_map[2] == DCA_TAG_MAP_VALID) &&
 		(tag_map[3] == DCA_TAG_MAP_VALID) &&
 		(tag_map[4] == DCA_TAG_MAP_VALID));
 }

 struct dca_provider *ioat_dca_init(struct pci_dev *pdev, void __iomem *iobase)
 {
 	struct dca_provider *dca;
 	struct ioat_dca_priv *ioatdca;
 	int slots;
 	int i;
 	int err;
 	u16 dca_offset;
 	u16 csi_fsb_control;
 	u16 pcie_control;
 	u8 bit;

 	union {
 		u64 full;
 		struct {
 			u32 low;
 			u32 high;
 		};
 	} tag_map;

 	if (!system_has_dca_enabled(pdev))
 		return NULL;

 	dca_offset = readw(iobase + IOAT_DCAOFFSET_OFFSET);
 	if (dca_offset == 0)
 		return NULL;

 	slots = ioat_dca_count_dca_slots(iobase, dca_offset);
 	if (slots == 0)
 		return NULL;

 	dca = alloc_dca_provider(&ioat_dca_ops,
 				 sizeof(*ioatdca)
 				      + (sizeof(struct ioat_dca_slot) * slots));
 	if (!dca)
 		return NULL;

 	ioatdca = dca_priv(dca);
 	ioatdca->iobase = iobase;
 	ioatdca->dca_base = iobase + dca_offset;
 	ioatdca->max_requesters = slots;

 	/* some bios might not know to turn these on */
 	csi_fsb_control = readw(ioatdca->dca_base + IOAT3_CSI_CONTROL_OFFSET);
 	if ((csi_fsb_control & IOAT3_CSI_CONTROL_PREFETCH) == 0) {
 		csi_fsb_control |= IOAT3_CSI_CONTROL_PREFETCH;
 		writew(csi_fsb_control,
 		       ioatdca->dca_base + IOAT3_CSI_CONTROL_OFFSET);
 	}
 	pcie_control = readw(ioatdca->dca_base + IOAT3_PCI_CONTROL_OFFSET);
 	if ((pcie_control & IOAT3_PCI_CONTROL_MEMWR) == 0) {
 		pcie_control |= IOAT3_PCI_CONTROL_MEMWR;
 		writew(pcie_control,
 		       ioatdca->dca_base + IOAT3_PCI_CONTROL_OFFSET);
 	}


 	/* TODO version, compatibility and configuration checks */

 	/* copy out the APIC to DCA tag map */
 	tag_map.low =
 		readl(ioatdca->dca_base + IOAT3_APICID_TAG_MAP_OFFSET_LOW);
 	tag_map.high =
 		readl(ioatdca->dca_base + IOAT3_APICID_TAG_MAP_OFFSET_HIGH);
 	for (i = 0; i < 8; i++) {
 		bit = tag_map.full >> (8 * i);
 		ioatdca->tag_map[i] = bit & DCA_TAG_MAP_MASK;
 	}

 	if (dca3_tag_map_invalid(ioatdca->tag_map)) {
 		WARN_TAINT_ONCE(1, TAINT_FIRMWARE_WORKAROUND,
 				"%s %s: APICID_TAG_MAP set incorrectly by BIOS, disabling DCA\n",
 				dev_driver_string(&pdev->dev),
 				dev_name(&pdev->dev));
 		free_dca_provider(dca);
 		return NULL;
 	}

 	err = register_dca_provider(dca, &pdev->dev);
 	if (err) {
 		free_dca_provider(dca);
 		return NULL;
 	}

 	return dca;
 }
	/*
	* Intel I/OAT DMA Linux driver
	* Copyright(c) 2007 - 2009 Intel Corporation.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms and conditions of the GNU General Public License,
	* version 2, as published by the Free Software Foundation.
	*
	* 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.
	*
	* The full GNU General Public License is included in this distribution in
	* the file called "COPYING".
	*
	*/

	#include <linux/kernel.h>
	#include <linux/pci.h>
	#include <linux/smp.h>
	#include <linux/interrupt.h>
	#include <linux/dca.h>

	/* either a kernel change is needed, or we need something like this in kernel */
	#ifndef CONFIG_SMP
	#include <asm/smp.h>
	#undef cpu_physical_id
	#define cpu_physical_id(cpu) (cpuid_ebx(1) >> 24)
	#endif

	#include "dma.h"
	#include "registers.h"

	/*
	* Bit 7 of a tag map entry is the "valid" bit, if it is set then bits 0:6
	* contain the bit number of the APIC ID to map into the DCA tag. If the valid
	* bit is not set, then the value must be 0 or 1 and defines the bit in the tag.
	*/
	#define DCA_TAG_MAP_VALID 0x80

	#define DCA3_TAG_MAP_BIT_TO_INV 0x80
	#define DCA3_TAG_MAP_BIT_TO_SEL 0x40
	#define DCA3_TAG_MAP_LITERAL_VAL 0x1

	#define DCA_TAG_MAP_MASK 0xDF

	/* expected tag map bytes for I/OAT ver.2 */
	#define DCA2_TAG_MAP_BYTE0 0x80
	#define DCA2_TAG_MAP_BYTE1 0x0
	#define DCA2_TAG_MAP_BYTE2 0x81
	#define DCA2_TAG_MAP_BYTE3 0x82
	#define DCA2_TAG_MAP_BYTE4 0x82

	/* verify if tag map matches expected values */
	static inline int dca2_tag_map_valid(u8 *tag_map)
	{
	return ((tag_map[0] == DCA2_TAG_MAP_BYTE0) &&
	(tag_map[1] == DCA2_TAG_MAP_BYTE1) &&
	(tag_map[2] == DCA2_TAG_MAP_BYTE2) &&
	(tag_map[3] == DCA2_TAG_MAP_BYTE3) &&
	(tag_map[4] == DCA2_TAG_MAP_BYTE4));
	}

	/*
	* "Legacy" DCA systems do not implement the DCA register set in the
	* I/OAT device. Software needs direct support for their tag mappings.
	*/

	#define APICID_BIT(x) (DCA_TAG_MAP_VALID \| (x))
	#define IOAT_TAG_MAP_LEN 8

	/* pack PCI B/D/F into a u16 */
	static inline u16 dcaid_from_pcidev(struct pci_dev *pci)
	{
	return (pci->bus->number << 8) \| pci->devfn;
	}

	static int dca_enabled_in_bios(struct pci_dev *pdev)
	{
	/* CPUID level 9 returns DCA configuration */
	/* Bit 0 indicates DCA enabled by the BIOS */
	unsigned long cpuid_level_9;
	int res;

	cpuid_level_9 = cpuid_eax(9);
	res = test_bit(0, &cpuid_level_9);
	if (!res)
	dev_dbg(&pdev->dev, "DCA is disabled in BIOS\n");

	return res;
	}

	int system_has_dca_enabled(struct pci_dev *pdev)
	{
	if (boot_cpu_has(X86_FEATURE_DCA))
	return dca_enabled_in_bios(pdev);

	dev_dbg(&pdev->dev, "boot cpu doesn't have X86_FEATURE_DCA\n");
	return 0;
	}

	struct ioat_dca_slot {
	struct pci_dev pdev; / requester device */
	u16 rid; /* requester id, as used by IOAT */
	};

	#define IOAT_DCA_MAX_REQ 6
	#define IOAT3_DCA_MAX_REQ 2

	struct ioat_dca_priv {
	void __iomem *iobase;
	void __iomem *dca_base;
	int max_requesters;
	int requester_count;
	u8 tag_map[IOAT_TAG_MAP_LEN];
	struct ioat_dca_slot req_slots[0];
	};

	static int ioat_dca_dev_managed(struct dca_provider *dca,
	struct device *dev)
	{
	struct ioat_dca_priv *ioatdca = dca_priv(dca);
	struct pci_dev *pdev;
	int i;

	pdev = to_pci_dev(dev);
	for (i = 0; i < ioatdca->max_requesters; i++) {
	if (ioatdca->req_slots[i].pdev == pdev)
	return 1;
	}
	return 0;
	}

	static int ioat_dca_add_requester(struct dca_provider dca, struct device dev)
	{
	struct ioat_dca_priv *ioatdca = dca_priv(dca);
	struct pci_dev *pdev;
	int i;
	u16 id;
	u16 global_req_table;

	/* This implementation only supports PCI-Express */
	if (!dev_is_pci(dev))
	return -ENODEV;
	pdev = to_pci_dev(dev);
	id = dcaid_from_pcidev(pdev);

	if (ioatdca->requester_count == ioatdca->max_requesters)
	return -ENODEV;

	for (i = 0; i < ioatdca->max_requesters; i++) {
	if (ioatdca->req_slots[i].pdev == NULL) {
	/* found an empty slot */
	ioatdca->requester_count++;
	ioatdca->req_slots[i].pdev = pdev;
	ioatdca->req_slots[i].rid = id;
	global_req_table =
	readw(ioatdca->dca_base + IOAT3_DCA_GREQID_OFFSET);
	writel(id \| IOAT_DCA_GREQID_VALID,
	ioatdca->iobase + global_req_table + (i * 4));
	return i;
	}
	}
	/* Error, ioatdma->requester_count is out of whack */
	return -EFAULT;
	}

	static int ioat_dca_remove_requester(struct dca_provider *dca,
	struct device *dev)
	{
	struct ioat_dca_priv *ioatdca = dca_priv(dca);
	struct pci_dev *pdev;
	int i;
	u16 global_req_table;

	/* This implementation only supports PCI-Express */
	if (!dev_is_pci(dev))
	return -ENODEV;
	pdev = to_pci_dev(dev);

	for (i = 0; i < ioatdca->max_requesters; i++) {
	if (ioatdca->req_slots[i].pdev == pdev) {
	global_req_table =
	readw(ioatdca->dca_base + IOAT3_DCA_GREQID_OFFSET);
	writel(0, ioatdca->iobase + global_req_table + (i * 4));
	ioatdca->req_slots[i].pdev = NULL;
	ioatdca->req_slots[i].rid = 0;
	ioatdca->requester_count--;
	return i;
	}
	}
	return -ENODEV;
	}

	static u8 ioat_dca_get_tag(struct dca_provider *dca,
	struct device *dev,
	int cpu)
	{
	u8 tag;

	struct ioat_dca_priv *ioatdca = dca_priv(dca);
	int i, apic_id, bit, value;
	u8 entry;

	tag = 0;
	apic_id = cpu_physical_id(cpu);

	for (i = 0; i < IOAT_TAG_MAP_LEN; i++) {
	entry = ioatdca->tag_map[i];
	if (entry & DCA3_TAG_MAP_BIT_TO_SEL) {
	bit = entry &
	~(DCA3_TAG_MAP_BIT_TO_SEL \| DCA3_TAG_MAP_BIT_TO_INV);
	value = (apic_id & (1 << bit)) ? 1 : 0;
	} else if (entry & DCA3_TAG_MAP_BIT_TO_INV) {
	bit = entry & ~DCA3_TAG_MAP_BIT_TO_INV;
	value = (apic_id & (1 << bit)) ? 0 : 1;
	} else {
	value = (entry & DCA3_TAG_MAP_LITERAL_VAL) ? 1 : 0;
	}
	tag \|= (value << i);
	}

	return tag;
	}

	static struct dca_ops ioat_dca_ops = {
	.add_requester = ioat_dca_add_requester,
	.remove_requester = ioat_dca_remove_requester,
	.get_tag = ioat_dca_get_tag,
	.dev_managed = ioat_dca_dev_managed,
	};

	static int ioat_dca_count_dca_slots(void *iobase, u16 dca_offset)
	{
	int slots = 0;
	u32 req;
	u16 global_req_table;

	global_req_table = readw(iobase + dca_offset + IOAT3_DCA_GREQID_OFFSET);
	if (global_req_table == 0)
	return 0;

	do {
	req = readl(iobase + global_req_table + (slots * sizeof(u32)));
	slots++;
	} while ((req & IOAT_DCA_GREQID_LASTID) == 0);

	return slots;
	}

	static inline int dca3_tag_map_invalid(u8 *tag_map)
	{
	/*
	* If the tag map is not programmed by the BIOS the default is:
	* 0x80 0x80 0x80 0x80 0x80 0x00 0x00 0x00
	*
	* This an invalid map and will result in only 2 possible tags
	* 0x1F and 0x00. 0x00 is an invalid DCA tag so we know that
	* this entire definition is invalid.
	*/
	return ((tag_map[0] == DCA_TAG_MAP_VALID) &&
	(tag_map[1] == DCA_TAG_MAP_VALID) &&
	(tag_map[2] == DCA_TAG_MAP_VALID) &&
	(tag_map[3] == DCA_TAG_MAP_VALID) &&
	(tag_map[4] == DCA_TAG_MAP_VALID));
	}

	struct dca_provider ioat_dca_init(struct pci_dev pdev, void __iomem *iobase)
	{
	struct dca_provider *dca;
	struct ioat_dca_priv *ioatdca;
	int slots;
	int i;
	int err;
	u16 dca_offset;
	u16 csi_fsb_control;
	u16 pcie_control;
	u8 bit;

	union {
	u64 full;
	struct {
	u32 low;
	u32 high;
	};
	} tag_map;

	if (!system_has_dca_enabled(pdev))
	return NULL;

	dca_offset = readw(iobase + IOAT_DCAOFFSET_OFFSET);
	if (dca_offset == 0)
	return NULL;

	slots = ioat_dca_count_dca_slots(iobase, dca_offset);
	if (slots == 0)
	return NULL;

	dca = alloc_dca_provider(&ioat_dca_ops,
	sizeof(*ioatdca)
	+ (sizeof(struct ioat_dca_slot) * slots));
	if (!dca)
	return NULL;

	ioatdca = dca_priv(dca);
	ioatdca->iobase = iobase;
	ioatdca->dca_base = iobase + dca_offset;
	ioatdca->max_requesters = slots;

	/* some bios might not know to turn these on */
	csi_fsb_control = readw(ioatdca->dca_base + IOAT3_CSI_CONTROL_OFFSET);
	if ((csi_fsb_control & IOAT3_CSI_CONTROL_PREFETCH) == 0) {
	csi_fsb_control \|= IOAT3_CSI_CONTROL_PREFETCH;
	writew(csi_fsb_control,
	ioatdca->dca_base + IOAT3_CSI_CONTROL_OFFSET);
	}
	pcie_control = readw(ioatdca->dca_base + IOAT3_PCI_CONTROL_OFFSET);
	if ((pcie_control & IOAT3_PCI_CONTROL_MEMWR) == 0) {
	pcie_control \|= IOAT3_PCI_CONTROL_MEMWR;
	writew(pcie_control,
	ioatdca->dca_base + IOAT3_PCI_CONTROL_OFFSET);
	}


	/* TODO version, compatibility and configuration checks */

	/* copy out the APIC to DCA tag map */
	tag_map.low =
	readl(ioatdca->dca_base + IOAT3_APICID_TAG_MAP_OFFSET_LOW);
	tag_map.high =
	readl(ioatdca->dca_base + IOAT3_APICID_TAG_MAP_OFFSET_HIGH);
	for (i = 0; i < 8; i++) {
	bit = tag_map.full >> (8 * i);
	ioatdca->tag_map[i] = bit & DCA_TAG_MAP_MASK;
	}

	if (dca3_tag_map_invalid(ioatdca->tag_map)) {
	WARN_TAINT_ONCE(1, TAINT_FIRMWARE_WORKAROUND,
	"%s %s: APICID_TAG_MAP set incorrectly by BIOS, disabling DCA\n",
	dev_driver_string(&pdev->dev),
	dev_name(&pdev->dev));
	free_dca_provider(dca);
	return NULL;
	}

	err = register_dca_provider(dca, &pdev->dev);
	if (err) {
	free_dca_provider(dca);
	return NULL;
	}

	return dca;
	}