drivers/dma/ioat_dca.c - kernel/msm-4.9 - Gitiles

 /*
  * Intel I/OAT DMA Linux driver
  * Copyright(c) 2007 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.
  *
  * You should have received a copy of the GNU General Public License along with
  * this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * 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 "ioatdma.h"
 #include "ioatdma_registers.h"

 /*
  * Bit 16 of a tag map entry is the "valid" bit, if it is set then bits 0:15
  * 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

 /*
  * "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

 static u8 ioat_tag_map_BNB[IOAT_TAG_MAP_LEN] = {
 	1, APICID_BIT(1), APICID_BIT(2), APICID_BIT(2), };
 static u8 ioat_tag_map_SCNB[IOAT_TAG_MAP_LEN] = {
 	1, APICID_BIT(1), APICID_BIT(2), APICID_BIT(2), };
 static u8 ioat_tag_map_CNB[IOAT_TAG_MAP_LEN] = {
 	1, APICID_BIT(1), APICID_BIT(3), APICID_BIT(4), APICID_BIT(2), };
 static u8 ioat_tag_map_UNISYS[IOAT_TAG_MAP_LEN] = { 0 };

 /* 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_err(&pdev->dev, "DCA is disabled in BIOS\n");

 	return res;
 }

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

 	dev_err(&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

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

 /* 5000 series chipset DCA Port Requester ID Table Entry Format
  * [15:8]	PCI-Express Bus Number
  * [7:3]	PCI-Express Device Number
  * [2:0]	PCI-Express Function Number
  *
  * 5000 series chipset DCA control register format
  * [7:1]	Reserved (0)
  * [0]		Ignore Function Number
  */

 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;

 	/* This implementation only supports PCI-Express */
 	if (dev->bus != &pci_bus_type)
 		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;
 			writew(id, ioatdca->dca_base + (i * 4));
 			/* make sure the ignore function bit is off */
 			writeb(0, ioatdca->dca_base + (i * 4) + 2);
 			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;

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

 	for (i = 0; i < ioatdca->max_requesters; i++) {
 		if (ioatdca->req_slots[i].pdev == pdev) {
 			writew(0, ioatdca->dca_base + (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, int cpu)
 {
 	struct ioat_dca_priv *ioatdca = dca_priv(dca);
 	int i, apic_id, bit, value;
 	u8 entry, tag;

 	tag = 0;
 	apic_id = cpu_physical_id(cpu);

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


 struct dca_provider *ioat_dca_init(struct pci_dev *pdev, void __iomem *iobase)
 {
 	struct dca_provider *dca;
 	struct ioat_dca_priv *ioatdca;
 	u8 *tag_map = NULL;
 	int i;
 	int err;

 	if (!system_has_dca_enabled(pdev))
 		return NULL;

 	/* I/OAT v1 systems must have a known tag_map to support DCA */
 	switch (pdev->vendor) {
 	case PCI_VENDOR_ID_INTEL:
 		switch (pdev->device) {
 		case PCI_DEVICE_ID_INTEL_IOAT:
 			tag_map = ioat_tag_map_BNB;
 			break;
 		case PCI_DEVICE_ID_INTEL_IOAT_CNB:
 			tag_map = ioat_tag_map_CNB;
 			break;
 		case PCI_DEVICE_ID_INTEL_IOAT_SCNB:
 			tag_map = ioat_tag_map_SCNB;
 			break;
 		}
 		break;
 	case PCI_VENDOR_ID_UNISYS:
 		switch (pdev->device) {
 		case PCI_DEVICE_ID_UNISYS_DMA_DIRECTOR:
 			tag_map = ioat_tag_map_UNISYS;
 			break;
 		}
 		break;
 	}
 	if (tag_map == NULL)
 		return NULL;

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

 	ioatdca = dca_priv(dca);
 	ioatdca->max_requesters = IOAT_DCA_MAX_REQ;

 	ioatdca->dca_base = iobase + 0x54;

 	/* copy over the APIC ID to DCA tag mapping */
 	for (i = 0; i < IOAT_TAG_MAP_LEN; i++)
 		ioatdca->tag_map[i] = tag_map[i];

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

 	return dca;
 }


 static int ioat2_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->bus != &pci_bus_type)
 		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 + IOAT_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 ioat2_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->bus != &pci_bus_type)
 		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 + IOAT_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 ioat2_dca_get_tag(struct dca_provider *dca, int cpu)
 {
 	u8 tag;

 	tag = ioat_dca_get_tag(dca, cpu);
 	tag = (~tag) & 0x1F;
 	return tag;
 }

 static struct dca_ops ioat2_dca_ops = {
 	.add_requester		= ioat2_dca_add_requester,
 	.remove_requester	= ioat2_dca_remove_requester,
 	.get_tag		= ioat2_dca_get_tag,
 };

 static int ioat2_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 + IOAT_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;
 }

 struct dca_provider *ioat2_dca_init(struct pci_dev *pdev, void __iomem *iobase)
 {
 	struct dca_provider *dca;
 	struct ioat_dca_priv *ioatdca;
 	int slots;
 	int i;
 	int err;
 	u32 tag_map;
 	u16 dca_offset;
 	u16 csi_fsb_control;
 	u16 pcie_control;
 	u8 bit;

 	if (!system_has_dca_enabled(pdev))
 		return NULL;

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

 	slots = ioat2_dca_count_dca_slots(iobase, dca_offset);
 	if (slots == 0)
 		return NULL;

 	dca = alloc_dca_provider(&ioat2_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 + IOAT_FSB_CAP_ENABLE_OFFSET);
 	if ((csi_fsb_control & IOAT_FSB_CAP_ENABLE_PREFETCH) == 0) {
 		csi_fsb_control |= IOAT_FSB_CAP_ENABLE_PREFETCH;
 		writew(csi_fsb_control,
 		       ioatdca->dca_base + IOAT_FSB_CAP_ENABLE_OFFSET);
 	}
 	pcie_control = readw(ioatdca->dca_base + IOAT_PCI_CAP_ENABLE_OFFSET);
 	if ((pcie_control & IOAT_PCI_CAP_ENABLE_MEMWR) == 0) {
 		pcie_control |= IOAT_PCI_CAP_ENABLE_MEMWR;
 		writew(pcie_control,
 		       ioatdca->dca_base + IOAT_PCI_CAP_ENABLE_OFFSET);
 	}


 	/* TODO version, compatibility and configuration checks */

 	/* copy out the APIC to DCA tag map */
 	tag_map = readl(ioatdca->dca_base + IOAT_APICID_TAG_MAP_OFFSET);
 	for (i = 0; i < 5; i++) {
 		bit = (tag_map >> (4 * i)) & 0x0f;
 		if (bit < 8)
 			ioatdca->tag_map[i] = bit | DCA_TAG_MAP_VALID;
 		else
 			ioatdca->tag_map[i] = 0;
 	}

 	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 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.
	*
	* You should have received a copy of the GNU General Public License along with
	* this program; if not, write to the Free Software Foundation, Inc.,
	* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* 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 "ioatdma.h"
	#include "ioatdma_registers.h"

	/*
	* Bit 16 of a tag map entry is the "valid" bit, if it is set then bits 0:15
	* 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

	/*
	* "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

	static u8 ioat_tag_map_BNB[IOAT_TAG_MAP_LEN] = {
	1, APICID_BIT(1), APICID_BIT(2), APICID_BIT(2), };
	static u8 ioat_tag_map_SCNB[IOAT_TAG_MAP_LEN] = {
	1, APICID_BIT(1), APICID_BIT(2), APICID_BIT(2), };
	static u8 ioat_tag_map_CNB[IOAT_TAG_MAP_LEN] = {
	1, APICID_BIT(1), APICID_BIT(3), APICID_BIT(4), APICID_BIT(2), };
	static u8 ioat_tag_map_UNISYS[IOAT_TAG_MAP_LEN] = { 0 };

	/* 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_err(&pdev->dev, "DCA is disabled in BIOS\n");

	return res;
	}

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

	dev_err(&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

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

	/* 5000 series chipset DCA Port Requester ID Table Entry Format
	* [15:8] PCI-Express Bus Number
	* [7:3] PCI-Express Device Number
	* [2:0] PCI-Express Function Number
	*
	* 5000 series chipset DCA control register format
	* [7:1] Reserved (0)
	* [0] Ignore Function Number
	*/

	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;

	/* This implementation only supports PCI-Express */
	if (dev->bus != &pci_bus_type)
	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;
	writew(id, ioatdca->dca_base + (i * 4));
	/* make sure the ignore function bit is off */
	writeb(0, ioatdca->dca_base + (i * 4) + 2);
	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;

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

	for (i = 0; i < ioatdca->max_requesters; i++) {
	if (ioatdca->req_slots[i].pdev == pdev) {
	writew(0, ioatdca->dca_base + (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, int cpu)
	{
	struct ioat_dca_priv *ioatdca = dca_priv(dca);
	int i, apic_id, bit, value;
	u8 entry, tag;

	tag = 0;
	apic_id = cpu_physical_id(cpu);

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


	struct dca_provider ioat_dca_init(struct pci_dev pdev, void __iomem *iobase)
	{
	struct dca_provider *dca;
	struct ioat_dca_priv *ioatdca;
	u8 *tag_map = NULL;
	int i;
	int err;

	if (!system_has_dca_enabled(pdev))
	return NULL;

	/* I/OAT v1 systems must have a known tag_map to support DCA */
	switch (pdev->vendor) {
	case PCI_VENDOR_ID_INTEL:
	switch (pdev->device) {
	case PCI_DEVICE_ID_INTEL_IOAT:
	tag_map = ioat_tag_map_BNB;
	break;
	case PCI_DEVICE_ID_INTEL_IOAT_CNB:
	tag_map = ioat_tag_map_CNB;
	break;
	case PCI_DEVICE_ID_INTEL_IOAT_SCNB:
	tag_map = ioat_tag_map_SCNB;
	break;
	}
	break;
	case PCI_VENDOR_ID_UNISYS:
	switch (pdev->device) {
	case PCI_DEVICE_ID_UNISYS_DMA_DIRECTOR:
	tag_map = ioat_tag_map_UNISYS;
	break;
	}
	break;
	}
	if (tag_map == NULL)
	return NULL;

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

	ioatdca = dca_priv(dca);
	ioatdca->max_requesters = IOAT_DCA_MAX_REQ;

	ioatdca->dca_base = iobase + 0x54;

	/* copy over the APIC ID to DCA tag mapping */
	for (i = 0; i < IOAT_TAG_MAP_LEN; i++)
	ioatdca->tag_map[i] = tag_map[i];

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

	return dca;
	}


	static int ioat2_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->bus != &pci_bus_type)
	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 + IOAT_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 ioat2_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->bus != &pci_bus_type)
	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 + IOAT_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 ioat2_dca_get_tag(struct dca_provider *dca, int cpu)
	{
	u8 tag;

	tag = ioat_dca_get_tag(dca, cpu);
	tag = (~tag) & 0x1F;
	return tag;
	}

	static struct dca_ops ioat2_dca_ops = {
	.add_requester = ioat2_dca_add_requester,
	.remove_requester = ioat2_dca_remove_requester,
	.get_tag = ioat2_dca_get_tag,
	};

	static int ioat2_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 + IOAT_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;
	}

	struct dca_provider ioat2_dca_init(struct pci_dev pdev, void __iomem *iobase)
	{
	struct dca_provider *dca;
	struct ioat_dca_priv *ioatdca;
	int slots;
	int i;
	int err;
	u32 tag_map;
	u16 dca_offset;
	u16 csi_fsb_control;
	u16 pcie_control;
	u8 bit;

	if (!system_has_dca_enabled(pdev))
	return NULL;

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

	slots = ioat2_dca_count_dca_slots(iobase, dca_offset);
	if (slots == 0)
	return NULL;

	dca = alloc_dca_provider(&ioat2_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 + IOAT_FSB_CAP_ENABLE_OFFSET);
	if ((csi_fsb_control & IOAT_FSB_CAP_ENABLE_PREFETCH) == 0) {
	csi_fsb_control \|= IOAT_FSB_CAP_ENABLE_PREFETCH;
	writew(csi_fsb_control,
	ioatdca->dca_base + IOAT_FSB_CAP_ENABLE_OFFSET);
	}
	pcie_control = readw(ioatdca->dca_base + IOAT_PCI_CAP_ENABLE_OFFSET);
	if ((pcie_control & IOAT_PCI_CAP_ENABLE_MEMWR) == 0) {
	pcie_control \|= IOAT_PCI_CAP_ENABLE_MEMWR;
	writew(pcie_control,
	ioatdca->dca_base + IOAT_PCI_CAP_ENABLE_OFFSET);
	}


	/* TODO version, compatibility and configuration checks */

	/* copy out the APIC to DCA tag map */
	tag_map = readl(ioatdca->dca_base + IOAT_APICID_TAG_MAP_OFFSET);
	for (i = 0; i < 5; i++) {
	bit = (tag_map >> (4 * i)) & 0x0f;
	if (bit < 8)
	ioatdca->tag_map[i] = bit \| DCA_TAG_MAP_VALID;
	else
	ioatdca->tag_map[i] = 0;
	}

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

	return dca;
	}