/*
 * This file implements the DMA operations for NVLink devices. The NPU
 * devices all point to the same iommu table as the parent PCI device.
 *
 * Copyright Alistair Popple, IBM Corporation 2015.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 */

#include <linux/slab.h>
#include <linux/mmu_notifier.h>
#include <linux/mmu_context.h>
#include <linux/of.h>
#include <linux/export.h>
#include <linux/pci.h>
#include <linux/memblock.h>
#include <linux/iommu.h>

#include <asm/tlb.h>
#include <asm/powernv.h>
#include <asm/reg.h>
#include <asm/opal.h>
#include <asm/io.h>
#include <asm/iommu.h>
#include <asm/pnv-pci.h>
#include <asm/msi_bitmap.h>
#include <asm/opal.h>

#include "powernv.h"
#include "pci.h"

#define npu_to_phb(x) container_of(x, struct pnv_phb, npu)

/*
 * spinlock to protect initialisation of an npu_context for a particular
 * mm_struct.
 */
static DEFINE_SPINLOCK(npu_context_lock);

/*
 * When an address shootdown range exceeds this threshold we invalidate the
 * entire TLB on the GPU for the given PID rather than each specific address in
 * the range.
 */
#define ATSD_THRESHOLD (2*1024*1024)

/*
 * Other types of TCE cache invalidation are not functional in the
 * hardware.
 */
static struct pci_dev *get_pci_dev(struct device_node *dn)
{
        struct pci_dn *pdn = PCI_DN(dn);

        return pci_get_domain_bus_and_slot(pci_domain_nr(pdn->phb->bus),
                                           pdn->busno, pdn->devfn);
}

/* Given a NPU device get the associated PCI device. */
struct pci_dev *pnv_pci_get_gpu_dev(struct pci_dev *npdev)
{
        struct device_node *dn;
        struct pci_dev *gpdev;

        if (WARN_ON(!npdev))
                return NULL;

        if (WARN_ON(!npdev->dev.of_node))
                return NULL;

        /* Get assoicated PCI device */
        dn = of_parse_phandle(npdev->dev.of_node, "ibm,gpu", 0);
        if (!dn)
                return NULL;

        gpdev = get_pci_dev(dn);
        of_node_put(dn);

        return gpdev;
}
EXPORT_SYMBOL(pnv_pci_get_gpu_dev);

/* Given the real PCI device get a linked NPU device. */
struct pci_dev *pnv_pci_get_npu_dev(struct pci_dev *gpdev, int index)
{
        struct device_node *dn;
        struct pci_dev *npdev;

        if (WARN_ON(!gpdev))
                return NULL;

        /* Not all PCI devices have device-tree nodes */
        if (!gpdev->dev.of_node)
                return NULL;

        /* Get assoicated PCI device */
        dn = of_parse_phandle(gpdev->dev.of_node, "ibm,npu", index);
        if (!dn)
                return NULL;

        npdev = get_pci_dev(dn);
        of_node_put(dn);

        return npdev;
}
EXPORT_SYMBOL(pnv_pci_get_npu_dev);

#define NPU_DMA_OP_UNSUPPORTED()                                        \
        dev_err_once(dev, "%s operation unsupported for NVLink devices\n", \
                __func__)

static void *dma_npu_alloc(struct device *dev, size_t size,
                           dma_addr_t *dma_handle, gfp_t flag,
                           unsigned long attrs)
{
        NPU_DMA_OP_UNSUPPORTED();
        return NULL;
}

static void dma_npu_free(struct device *dev, size_t size,
                         void *vaddr, dma_addr_t dma_handle,
                         unsigned long attrs)
{
        NPU_DMA_OP_UNSUPPORTED();
}

static dma_addr_t dma_npu_map_page(struct device *dev, struct page *page,
                                   unsigned long offset, size_t size,
                                   enum dma_data_direction direction,
                                   unsigned long attrs)
{
        NPU_DMA_OP_UNSUPPORTED();
        return 0;
}

static int dma_npu_map_sg(struct device *dev, struct scatterlist *sglist,
                          int nelems, enum dma_data_direction direction,
                          unsigned long attrs)
{
        NPU_DMA_OP_UNSUPPORTED();
        return 0;
}

static int dma_npu_dma_supported(struct device *dev, u64 mask)
{
        NPU_DMA_OP_UNSUPPORTED();
        return 0;
}

static u64 dma_npu_get_required_mask(struct device *dev)
{
        NPU_DMA_OP_UNSUPPORTED();
        return 0;
}

static const struct dma_map_ops dma_npu_ops = {
        .map_page               = dma_npu_map_page,
        .map_sg                 = dma_npu_map_sg,
        .alloc                  = dma_npu_alloc,
        .free                   = dma_npu_free,
        .dma_supported          = dma_npu_dma_supported,
        .get_required_mask      = dma_npu_get_required_mask,
};

/*
 * Returns the PE assoicated with the PCI device of the given
 * NPU. Returns the linked pci device if pci_dev != NULL.
 */
static struct pnv_ioda_pe *get_gpu_pci_dev_and_pe(struct pnv_ioda_pe *npe,
                                                  struct pci_dev **gpdev)
{
        struct pnv_phb *phb;
        struct pci_controller *hose;
        struct pci_dev *pdev;
        struct pnv_ioda_pe *pe;
        struct pci_dn *pdn;

        pdev = pnv_pci_get_gpu_dev(npe->pdev);
        if (!pdev)
                return NULL;

        pdn = pci_get_pdn(pdev);
        if (WARN_ON(!pdn || pdn->pe_number == IODA_INVALID_PE))
                return NULL;

        hose = pci_bus_to_host(pdev->bus);
        phb = hose->private_data;
        pe = &phb->ioda.pe_array[pdn->pe_number];

        if (gpdev)
                *gpdev = pdev;

        return pe;
}

long pnv_npu_set_window(struct pnv_ioda_pe *npe, int num,
                struct iommu_table *tbl)
{
        struct pnv_phb *phb = npe->phb;
        int64_t rc;
        const unsigned long size = tbl->it_indirect_levels ?
                tbl->it_level_size : tbl->it_size;
        const __u64 start_addr = tbl->it_offset << tbl->it_page_shift;
        const __u64 win_size = tbl->it_size << tbl->it_page_shift;

        pe_info(npe, "Setting up window %llx..%llx pg=%lx\n",
                        start_addr, start_addr + win_size - 1,
                        IOMMU_PAGE_SIZE(tbl));

        rc = opal_pci_map_pe_dma_window(phb->opal_id,
                        npe->pe_number,
                        npe->pe_number,
                        tbl->it_indirect_levels + 1,
                        __pa(tbl->it_base),
                        size << 3,
                        IOMMU_PAGE_SIZE(tbl));
        if (rc) {
                pe_err(npe, "Failed to configure TCE table, err %lld\n", rc);
                return rc;
        }
        pnv_pci_ioda2_tce_invalidate_entire(phb, false);

        /* Add the table to the list so its TCE cache will get invalidated */
        pnv_pci_link_table_and_group(phb->hose->node, num,
                        tbl, &npe->table_group);

        return 0;
}

long pnv_npu_unset_window(struct pnv_ioda_pe *npe, int num)
{
        struct pnv_phb *phb = npe->phb;
        int64_t rc;

        pe_info(npe, "Removing DMA window\n");

        rc = opal_pci_map_pe_dma_window(phb->opal_id, npe->pe_number,
                        npe->pe_number,
                        0/* levels */, 0/* table address */,
                        0/* table size */, 0/* page size */);
        if (rc) {
                pe_err(npe, "Unmapping failed, ret = %lld\n", rc);
                return rc;
        }
        pnv_pci_ioda2_tce_invalidate_entire(phb, false);

        pnv_pci_unlink_table_and_group(npe->table_group.tables[num],
                        &npe->table_group);

        return 0;
}

/*
 * Enables 32 bit DMA on NPU.
 */
static void pnv_npu_dma_set_32(struct pnv_ioda_pe *npe)
{
        struct pci_dev *gpdev;
        struct pnv_ioda_pe *gpe;
        int64_t rc;

        /*
         * Find the assoicated PCI devices and get the dma window
         * information from there.
         */
        if (!npe->pdev || !(npe->flags & PNV_IODA_PE_DEV))
                return;

        gpe = get_gpu_pci_dev_and_pe(npe, &gpdev);
        if (!gpe)
                return;

        rc = pnv_npu_set_window(npe, 0, gpe->table_group.tables[0]);

        /*
         * We don't initialise npu_pe->tce32_table as we always use
         * dma_npu_ops which are nops.
         */
        set_dma_ops(&npe->pdev->dev, &dma_npu_ops);
}

/*
 * Enables bypass mode on the NPU. The NPU only supports one
 * window per link, so bypass needs to be explicitly enabled or
 * disabled. Unlike for a PHB3 bypass and non-bypass modes can't be
 * active at the same time.
 */
static int pnv_npu_dma_set_bypass(struct pnv_ioda_pe *npe)
{
        struct pnv_phb *phb = npe->phb;
        int64_t rc = 0;
        phys_addr_t top = memblock_end_of_DRAM();

        if (phb->type != PNV_PHB_NPU_NVLINK || !npe->pdev)
                return -EINVAL;

        rc = pnv_npu_unset_window(npe, 0);
        if (rc != OPAL_SUCCESS)
                return rc;

        /* Enable the bypass window */

        top = roundup_pow_of_two(top);
        dev_info(&npe->pdev->dev, "Enabling bypass for PE %x\n",
                        npe->pe_number);
        rc = opal_pci_map_pe_dma_window_real(phb->opal_id,
                        npe->pe_number, npe->pe_number,
                        0 /* bypass base */, top);

        if (rc == OPAL_SUCCESS)
                pnv_pci_ioda2_tce_invalidate_entire(phb, false);

        return rc;
}

void pnv_npu_try_dma_set_bypass(struct pci_dev *gpdev, bool bypass)
{
        int i;
        struct pnv_phb *phb;
        struct pci_dn *pdn;
        struct pnv_ioda_pe *npe;
        struct pci_dev *npdev;

        for (i = 0; ; ++i) {
                npdev = pnv_pci_get_npu_dev(gpdev, i);

                if (!npdev)
                        break;

                pdn = pci_get_pdn(npdev);
                if (WARN_ON(!pdn || pdn->pe_number == IODA_INVALID_PE))
                        return;

                phb = pci_bus_to_host(npdev->bus)->private_data;

                /* We only do bypass if it's enabled on the linked device */
                npe = &phb->ioda.pe_array[pdn->pe_number];

                if (bypass) {
                        dev_info(&npdev->dev,
                                        "Using 64-bit DMA iommu bypass\n");
                        pnv_npu_dma_set_bypass(npe);
                } else {
                        dev_info(&npdev->dev, "Using 32-bit DMA via iommu\n");
                        pnv_npu_dma_set_32(npe);
                }
        }
}

/* Switch ownership from platform code to external user (e.g. VFIO) */
void pnv_npu_take_ownership(struct pnv_ioda_pe *npe)
{
        struct pnv_phb *phb = npe->phb;
        int64_t rc;

        /*
         * Note: NPU has just a single TVE in the hardware which means that
         * while used by the kernel, it can have either 32bit window or
         * DMA bypass but never both. So we deconfigure 32bit window only
         * if it was enabled at the moment of ownership change.
         */
        if (npe->table_group.tables[0]) {
                pnv_npu_unset_window(npe, 0);
                return;
        }

        /* Disable bypass */
        rc = opal_pci_map_pe_dma_window_real(phb->opal_id,
                        npe->pe_number, npe->pe_number,
                        0 /* bypass base */, 0);
        if (rc) {
                pe_err(npe, "Failed to disable bypass, err %lld\n", rc);
                return;
        }
        pnv_pci_ioda2_tce_invalidate_entire(npe->phb, false);
}

struct pnv_ioda_pe *pnv_pci_npu_setup_iommu(struct pnv_ioda_pe *npe)
{
        struct pnv_phb *phb = npe->phb;
        struct pci_bus *pbus = phb->hose->bus;
        struct pci_dev *npdev, *gpdev = NULL, *gptmp;
        struct pnv_ioda_pe *gpe = get_gpu_pci_dev_and_pe(npe, &gpdev);

        if (!gpe || !gpdev)
                return NULL;

        list_for_each_entry(npdev, &pbus->devices, bus_list) {
                gptmp = pnv_pci_get_gpu_dev(npdev);

                if (gptmp != gpdev)
                        continue;

                pe_info(gpe, "Attached NPU %s\n", dev_name(&npdev->dev));
                iommu_group_add_device(gpe->table_group.group, &npdev->dev);
        }

        return gpe;
}

/* Maximum number of nvlinks per npu */
#define NV_MAX_LINKS 6

/* Maximum index of npu2 hosts in the system. Always < NV_MAX_NPUS */
static int max_npu2_index;

struct npu_context {
        struct mm_struct *mm;
        struct pci_dev *npdev[NV_MAX_NPUS][NV_MAX_LINKS];
        struct mmu_notifier mn;
        struct kref kref;
        bool nmmu_flush;

        /* Callback to stop translation requests on a given GPU */
        void (*release_cb)(struct npu_context *context, void *priv);

        /*
         * Private pointer passed to the above callback for usage by
         * device drivers.
         */
        void *priv;
};

struct mmio_atsd_reg {
        struct npu *npu;
        int reg;
};

/*
 * Find a free MMIO ATSD register and mark it in use. Return -ENOSPC
 * if none are available.
 */
static int get_mmio_atsd_reg(struct npu *npu)
{
        int i;

        for (i = 0; i < npu->mmio_atsd_count; i++) {
                if (!test_and_set_bit_lock(i, &npu->mmio_atsd_usage))
                        return i;
        }

        return -ENOSPC;
}

static void put_mmio_atsd_reg(struct npu *npu, int reg)
{
        clear_bit_unlock(reg, &npu->mmio_atsd_usage);
}

/* MMIO ATSD register offsets */
#define XTS_ATSD_AVA  1
#define XTS_ATSD_STAT 2

static void mmio_launch_invalidate(struct mmio_atsd_reg *mmio_atsd_reg,
                                unsigned long launch, unsigned long va)
{
        struct npu *npu = mmio_atsd_reg->npu;
        int reg = mmio_atsd_reg->reg;

        __raw_writeq(cpu_to_be64(va),
                npu->mmio_atsd_regs[reg] + XTS_ATSD_AVA);
        eieio();
        __raw_writeq(cpu_to_be64(launch), npu->mmio_atsd_regs[reg]);
}

static void mmio_invalidate_pid(struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS],
                                unsigned long pid, bool flush)
{
        int i;
        unsigned long launch;

        for (i = 0; i <= max_npu2_index; i++) {
                if (mmio_atsd_reg[i].reg < 0)
                        continue;

                /* IS set to invalidate matching PID */
                launch = PPC_BIT(12);

                /* PRS set to process-scoped */
                launch |= PPC_BIT(13);

                /* AP */
                launch |= (u64)
                        mmu_get_ap(mmu_virtual_psize) << PPC_BITLSHIFT(17);

                /* PID */
                launch |= pid << PPC_BITLSHIFT(38);

                /* No flush */
                launch |= !flush << PPC_BITLSHIFT(39);

                /* Invalidating the entire process doesn't use a va */
                mmio_launch_invalidate(&mmio_atsd_reg[i], launch, 0);
        }
}

static void mmio_invalidate_va(struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS],
                        unsigned long va, unsigned long pid, bool flush)
{
        int i;
        unsigned long launch;

        for (i = 0; i <= max_npu2_index; i++) {
                if (mmio_atsd_reg[i].reg < 0)
                        continue;

                /* IS set to invalidate target VA */
                launch = 0;

                /* PRS set to process scoped */
                launch |= PPC_BIT(13);

                /* AP */
                launch |= (u64)
                        mmu_get_ap(mmu_virtual_psize) << PPC_BITLSHIFT(17);

                /* PID */
                launch |= pid << PPC_BITLSHIFT(38);

                /* No flush */
                launch |= !flush << PPC_BITLSHIFT(39);

                mmio_launch_invalidate(&mmio_atsd_reg[i], launch, va);
        }
}

#define mn_to_npu_context(x) container_of(x, struct npu_context, mn)

static void mmio_invalidate_wait(
        struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS])
{
        struct npu *npu;
        int i, reg;

        /* Wait for all invalidations to complete */
        for (i = 0; i <= max_npu2_index; i++) {
                if (mmio_atsd_reg[i].reg < 0)
                        continue;

                /* Wait for completion */
                npu = mmio_atsd_reg[i].npu;
                reg = mmio_atsd_reg[i].reg;
                while (__raw_readq(npu->mmio_atsd_regs[reg] + XTS_ATSD_STAT))
                        cpu_relax();
        }
}

/*
 * Acquires all the address translation shootdown (ATSD) registers required to
 * launch an ATSD on all links this npu_context is active on.
 */
static void acquire_atsd_reg(struct npu_context *npu_context,
                        struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS])
{
        int i, j;
        struct npu *npu;
        struct pci_dev *npdev;
        struct pnv_phb *nphb;

        for (i = 0; i <= max_npu2_index; i++) {
                mmio_atsd_reg[i].reg = -1;
                for (j = 0; j < NV_MAX_LINKS; j++) {
                        /*
                         * There are no ordering requirements with respect to
                         * the setup of struct npu_context, but to ensure
                         * consistent behaviour we need to ensure npdev[][] is
                         * only read once.
                         */
                        npdev = READ_ONCE(npu_context->npdev[i][j]);
                        if (!npdev)
                                continue;

                        nphb = pci_bus_to_host(npdev->bus)->private_data;
                        npu = &nphb->npu;
                        mmio_atsd_reg[i].npu = npu;
                        mmio_atsd_reg[i].reg = get_mmio_atsd_reg(npu);
                        while (mmio_atsd_reg[i].reg < 0) {
                                mmio_atsd_reg[i].reg = get_mmio_atsd_reg(npu);
                                cpu_relax();
                        }
                        break;
                }
        }
}

/*
 * Release previously acquired ATSD registers. To avoid deadlocks the registers
 * must be released in the same order they were acquired above in
 * acquire_atsd_reg.
 */
static void release_atsd_reg(struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS])
{
        int i;

        for (i = 0; i <= max_npu2_index; i++) {
                /*
                 * We can't rely on npu_context->npdev[][] being the same here
                 * as when acquire_atsd_reg() was called, hence we use the
                 * values stored in mmio_atsd_reg during the acquire phase
                 * rather than re-reading npdev[][].
                 */
                if (mmio_atsd_reg[i].reg < 0)
                        continue;

                put_mmio_atsd_reg(mmio_atsd_reg[i].npu, mmio_atsd_reg[i].reg);
        }
}

/*
 * Invalidate either a single address or an entire PID depending on
 * the value of va.
 */
static void mmio_invalidate(struct npu_context *npu_context, int va,
                        unsigned long address, bool flush)
{
        struct mmio_atsd_reg mmio_atsd_reg[NV_MAX_NPUS];
        unsigned long pid = npu_context->mm->context.id;

        if (npu_context->nmmu_flush)
                /*
                 * Unfortunately the nest mmu does not support flushing specific
                 * addresses so we have to flush the whole mm once before
                 * shooting down the GPU translation.
                 */
                flush_all_mm(npu_context->mm);

        /*
         * Loop over all the NPUs this process is active on and launch
         * an invalidate.
         */
        acquire_atsd_reg(npu_context, mmio_atsd_reg);
        if (va)
                mmio_invalidate_va(mmio_atsd_reg, address, pid, flush);
        else
                mmio_invalidate_pid(mmio_atsd_reg, pid, flush);

        mmio_invalidate_wait(mmio_atsd_reg);
        if (flush) {
                /*
                 * The GPU requires two flush ATSDs to ensure all entries have
                 * been flushed. We use PID 0 as it will never be used for a
                 * process on the GPU.
                 */
                mmio_invalidate_pid(mmio_atsd_reg, 0, true);
                mmio_invalidate_wait(mmio_atsd_reg);
                mmio_invalidate_pid(mmio_atsd_reg, 0, true);
                mmio_invalidate_wait(mmio_atsd_reg);
        }
        release_atsd_reg(mmio_atsd_reg);
}

static void pnv_npu2_mn_release(struct mmu_notifier *mn,
                                struct mm_struct *mm)
{
        struct npu_context *npu_context = mn_to_npu_context(mn);

        /* Call into device driver to stop requests to the NMMU */
        if (npu_context->release_cb)
                npu_context->release_cb(npu_context, npu_context->priv);

        /*
         * There should be no more translation requests for this PID, but we
         * need to ensure any entries for it are removed from the TLB.
         */
        mmio_invalidate(npu_context, 0, 0, true);
}

static void pnv_npu2_mn_change_pte(struct mmu_notifier *mn,
                                struct mm_struct *mm,
                                unsigned long address,
                                pte_t pte)
{
        struct npu_context *npu_context = mn_to_npu_context(mn);

        mmio_invalidate(npu_context, 1, address, true);
}

static void pnv_npu2_mn_invalidate_range(struct mmu_notifier *mn,
                                        struct mm_struct *mm,
                                        unsigned long start, unsigned long end)
{
        struct npu_context *npu_context = mn_to_npu_context(mn);
        unsigned long address;

        if (end - start > ATSD_THRESHOLD) {
                /*
                 * Just invalidate the entire PID if the address range is too
                 * large.
                 */
                mmio_invalidate(npu_context, 0, 0, true);
        } else {
                for (address = start; address < end; address += PAGE_SIZE)
                        mmio_invalidate(npu_context, 1, address, false);

                /* Do the flush only on the final addess == end */
                mmio_invalidate(npu_context, 1, address, true);
        }
}

static const struct mmu_notifier_ops nv_nmmu_notifier_ops = {
        .release = pnv_npu2_mn_release,
        .change_pte = pnv_npu2_mn_change_pte,
        .invalidate_range = pnv_npu2_mn_invalidate_range,
};

/*
 * Call into OPAL to setup the nmmu context for the current task in
 * the NPU. This must be called to setup the context tables before the
 * GPU issues ATRs. pdev should be a pointed to PCIe GPU device.
 *
 * A release callback should be registered to allow a device driver to
 * be notified that it should not launch any new translation requests
 * as the final TLB invalidate is about to occur.
 *
 * Returns an error if there no contexts are currently available or a
 * npu_context which should be passed to pnv_npu2_handle_fault().
 *
 * mmap_sem must be held in write mode and must not be called from interrupt
 * context.
 */
struct npu_context *pnv_npu2_init_context(struct pci_dev *gpdev,
                        unsigned long flags,
                        void (*cb)(struct npu_context *, void *),
                        void *priv)
{
        int rc;
        u32 nvlink_index;
        struct device_node *nvlink_dn;
        struct mm_struct *mm = current->mm;
        struct pnv_phb *nphb;
        struct npu *npu;
        struct npu_context *npu_context;

        /*
         * At present we don't support GPUs connected to multiple NPUs and I'm
         * not sure the hardware does either.
         */
        struct pci_dev *npdev = pnv_pci_get_npu_dev(gpdev, 0);

        if (!firmware_has_feature(FW_FEATURE_OPAL))
                return ERR_PTR(-ENODEV);

        if (!npdev)
                /* No nvlink associated with this GPU device */
                return ERR_PTR(-ENODEV);

        nvlink_dn = of_parse_phandle(npdev->dev.of_node, "ibm,nvlink", 0);
        if (WARN_ON(of_property_read_u32(nvlink_dn, "ibm,npu-link-index",
                                                        &nvlink_index)))
                return ERR_PTR(-ENODEV);

        if (!mm || mm->context.id == 0) {
                /*
                 * Kernel thread contexts are not supported and context id 0 is
                 * reserved on the GPU.
                 */
                return ERR_PTR(-EINVAL);
        }

        nphb = pci_bus_to_host(npdev->bus)->private_data;
        npu = &nphb->npu;

        /*
         * Setup the NPU context table for a particular GPU. These need to be
         * per-GPU as we need the tables to filter ATSDs when there are no
         * active contexts on a particular GPU. It is safe for these to be
         * called concurrently with destroy as the OPAL call takes appropriate
         * locks and refcounts on init/destroy.
         */
        rc = opal_npu_init_context(nphb->opal_id, mm->context.id, flags,
                                PCI_DEVID(gpdev->bus->number, gpdev->devfn));
        if (rc < 0)
                return ERR_PTR(-ENOSPC);

        /*
         * We store the npu pci device so we can more easily get at the
         * associated npus.
         */
        spin_lock(&npu_context_lock);
        npu_context = mm->context.npu_context;
        if (npu_context) {
                if (npu_context->release_cb != cb ||
                        npu_context->priv != priv) {
                        spin_unlock(&npu_context_lock);
                        opal_npu_destroy_context(nphb->opal_id, mm->context.id,
                                                PCI_DEVID(gpdev->bus->number,
                                                        gpdev->devfn));
                        return ERR_PTR(-EINVAL);
                }

                WARN_ON(!kref_get_unless_zero(&npu_context->kref));
        }
        spin_unlock(&npu_context_lock);

        if (!npu_context) {
                /*
                 * We can set up these fields without holding the
                 * npu_context_lock as the npu_context hasn't been returned to
                 * the caller meaning it can't be destroyed. Parallel allocation
                 * is protected against by mmap_sem.
                 */
                rc = -ENOMEM;
                npu_context = kzalloc(sizeof(struct npu_context), GFP_KERNEL);
                if (npu_context) {
                        kref_init(&npu_context->kref);
                        npu_context->mm = mm;
                        npu_context->mn.ops = &nv_nmmu_notifier_ops;
                        rc = __mmu_notifier_register(&npu_context->mn, mm);
                }

                if (rc) {
                        kfree(npu_context);
                        opal_npu_destroy_context(nphb->opal_id, mm->context.id,
                                        PCI_DEVID(gpdev->bus->number,
                                                gpdev->devfn));
                        return ERR_PTR(rc);
                }

                mm->context.npu_context = npu_context;
        }

        npu_context->release_cb = cb;
        npu_context->priv = priv;

        /*
         * npdev is a pci_dev pointer setup by the PCI code. We assign it to
         * npdev[][] to indicate to the mmu notifiers that an invalidation
         * should also be sent over this nvlink. The notifiers don't use any
         * other fields in npu_context, so we just need to ensure that when they
         * deference npu_context->npdev[][] it is either a valid pointer or
         * NULL.
         */
        WRITE_ONCE(npu_context->npdev[npu->index][nvlink_index], npdev);

        if (!nphb->npu.nmmu_flush) {
                /*
                 * If we're not explicitly flushing ourselves we need to mark
                 * the thread for global flushes
                 */
                npu_context->nmmu_flush = false;
                mm_context_add_copro(mm);
        } else
                npu_context->nmmu_flush = true;

        return npu_context;
}
EXPORT_SYMBOL(pnv_npu2_init_context);

static void pnv_npu2_release_context(struct kref *kref)
{
        struct npu_context *npu_context =
                container_of(kref, struct npu_context, kref);

        if (!npu_context->nmmu_flush)
                mm_context_remove_copro(npu_context->mm);

        npu_context->mm->context.npu_context = NULL;
}

/*
 * Destroy a context on the given GPU. May free the npu_context if it is no
 * longer active on any GPUs. Must not be called from interrupt context.
 */
void pnv_npu2_destroy_context(struct npu_context *npu_context,
                        struct pci_dev *gpdev)
{
        int removed;
        struct pnv_phb *nphb;
        struct npu *npu;
        struct pci_dev *npdev = pnv_pci_get_npu_dev(gpdev, 0);
        struct device_node *nvlink_dn;
        u32 nvlink_index;

        if (WARN_ON(!npdev))
                return;

        if (!firmware_has_feature(FW_FEATURE_OPAL))
                return;

        nphb = pci_bus_to_host(npdev->bus)->private_data;
        npu = &nphb->npu;
        nvlink_dn = of_parse_phandle(npdev->dev.of_node, "ibm,nvlink", 0);
        if (WARN_ON(of_property_read_u32(nvlink_dn, "ibm,npu-link-index",
                                                        &nvlink_index)))
                return;
        WRITE_ONCE(npu_context->npdev[npu->index][nvlink_index], NULL);
        opal_npu_destroy_context(nphb->opal_id, npu_context->mm->context.id,
                                PCI_DEVID(gpdev->bus->number, gpdev->devfn));
        spin_lock(&npu_context_lock);
        removed = kref_put(&npu_context->kref, pnv_npu2_release_context);
        spin_unlock(&npu_context_lock);

        /*
         * We need to do this outside of pnv_npu2_release_context so that it is
         * outside the spinlock as mmu_notifier_destroy uses SRCU.
         */
        if (removed) {
                mmu_notifier_unregister(&npu_context->mn,
                                        npu_context->mm);

                kfree(npu_context);
        }

}
EXPORT_SYMBOL(pnv_npu2_destroy_context);

/*
 * Assumes mmap_sem is held for the contexts associated mm.
 */
int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea,
                        unsigned long *flags, unsigned long *status, int count)
{
        u64 rc = 0, result = 0;
        int i, is_write;
        struct page *page[1];

        /* mmap_sem should be held so the struct_mm must be present */
        struct mm_struct *mm = context->mm;

        if (!firmware_has_feature(FW_FEATURE_OPAL))
                return -ENODEV;

        WARN_ON(!rwsem_is_locked(&mm->mmap_sem));

        for (i = 0; i < count; i++) {
                is_write = flags[i] & NPU2_WRITE;
                rc = get_user_pages_remote(NULL, mm, ea[i], 1,
                                        is_write ? FOLL_WRITE : 0,
                                        page, NULL, NULL);

                /*
                 * To support virtualised environments we will have to do an
                 * access to the page to ensure it gets faulted into the
                 * hypervisor. For the moment virtualisation is not supported in
                 * other areas so leave the access out.
                 */
                if (rc != 1) {
                        status[i] = rc;
                        result = -EFAULT;
                        continue;
                }

                status[i] = 0;
                put_page(page[0]);
        }

        return result;
}
EXPORT_SYMBOL(pnv_npu2_handle_fault);

int pnv_npu2_init(struct pnv_phb *phb)
{
        unsigned int i;
        u64 mmio_atsd;
        struct device_node *dn;
        struct pci_dev *gpdev;
        static int npu_index;
        uint64_t rc = 0;

        phb->npu.nmmu_flush =
                of_property_read_bool(phb->hose->dn, "ibm,nmmu-flush");
        for_each_child_of_node(phb->hose->dn, dn) {
                gpdev = pnv_pci_get_gpu_dev(get_pci_dev(dn));
                if (gpdev) {
                        rc = opal_npu_map_lpar(phb->opal_id,
                                PCI_DEVID(gpdev->bus->number, gpdev->devfn),
                                0, 0);
                        if (rc)
                                dev_err(&gpdev->dev,
                                        "Error %lld mapping device to LPAR\n",
                                        rc);
                }
        }

        for (i = 0; !of_property_read_u64_index(phb->hose->dn, "ibm,mmio-atsd",
                                                        i, &mmio_atsd); i++)
                phb->npu.mmio_atsd_regs[i] = ioremap(mmio_atsd, 32);

        pr_info("NPU%lld: Found %d MMIO ATSD registers", phb->opal_id, i);
        phb->npu.mmio_atsd_count = i;
        phb->npu.mmio_atsd_usage = 0;
        npu_index++;
        if (WARN_ON(npu_index >= NV_MAX_NPUS))
                return -ENOSPC;
        max_npu2_index = npu_index;
        phb->npu.index = npu_index;

        return 0;
}