// SPDX-License-Identifier: GPL-2.0-only
/*
 * Intel I/OAT DMA Linux driver
 * Copyright(c) 2007 - 2009 Intel Corporation.
 */

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

#include <asm/cpuid/api.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

/*
 * "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_dev_id(pci);
}

static int dca_enabled_in_bios(struct pci_dev *pdev)
{
        /* CPUID level 9 returns DCA configuration */
        /* Bit 0 indicates DCA enabled by the BIOS */
        u32 eax;
        int res;

        eax = cpuid_eax(CPUID_LEAF_DCA);
        res = eax & BIT(0);
        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[];
};

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 const 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,
                                 struct_size(ioatdca, req_slots, 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)) {
                add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
                pr_warn_once("%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;
}