// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright IBM Corp. 2020
 *
 * Author(s):
 *   Pierre Morel <pmorel@linux.ibm.com>
 *
 */

#define pr_fmt(fmt) "zpci: " fmt

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/seq_file.h>
#include <linux/irqdomain.h>
#include <linux/jump_label.h>
#include <linux/pci.h>
#include <linux/printk.h>
#include <linux/dma-direct.h>

#include <asm/pci_clp.h>
#include <asm/pci_dma.h>

#include "pci_bus.h"
#include "pci_iov.h"

static LIST_HEAD(zbus_list);
static DEFINE_MUTEX(zbus_list_lock);
static int zpci_nb_devices;

/* zpci_bus_prepare_device - Prepare a zPCI function for scanning
 * @zdev: the zPCI function to be prepared
 *
 * The PCI resources for the function are set up and added to its zbus and the
 * function is enabled. The function must be added to a zbus which must have
 * a PCI bus created. If an error occurs the zPCI function is not enabled.
 *
 * Return: 0 on success, an error code otherwise
 */
static int zpci_bus_prepare_device(struct zpci_dev *zdev)
{
        int rc, i;

        if (!zdev_enabled(zdev)) {
                rc = zpci_enable_device(zdev);
                if (rc) {
                        pr_err("Enabling PCI function %08x failed\n", zdev->fid);
                        return rc;
                }
        }

        if (!zdev->has_resources) {
                zpci_setup_bus_resources(zdev);
                for (i = 0; i < PCI_STD_NUM_BARS; i++) {
                        if (zdev->bars[i].res)
                                pci_bus_add_resource(zdev->zbus->bus, zdev->bars[i].res);
                }
        }

        return 0;
}

/* zpci_bus_scan_device - Scan a single device adding it to the PCI core
 * @zdev: the zdev to be scanned
 *
 * Scans the PCI function making it available to the common PCI code.
 *
 * Return: 0 on success, an error value otherwise
 */
int zpci_bus_scan_device(struct zpci_dev *zdev)
{
        struct pci_dev *pdev;
        int rc;

        rc = zpci_bus_prepare_device(zdev);
        if (rc)
                return rc;

        pdev = pci_scan_single_device(zdev->zbus->bus, zdev->devfn);
        if (!pdev)
                return -ENODEV;

        pci_lock_rescan_remove();
        pci_bus_add_device(pdev);
        pci_unlock_rescan_remove();

        return 0;
}

/* zpci_bus_remove_device - Removes the given zdev from the PCI core
 * @zdev: the zdev to be removed from the PCI core
 * @set_error: if true the device's error state is set to permanent failure
 *
 * Sets a zPCI device to a configured but offline state; the zPCI
 * device is still accessible through its hotplug slot and the zPCI
 * API but is removed from the common code PCI bus, making it
 * no longer available to drivers.
 */
void zpci_bus_remove_device(struct zpci_dev *zdev, bool set_error)
{
        struct zpci_bus *zbus = zdev->zbus;
        struct pci_dev *pdev;

        if (!zdev->zbus->bus)
                return;

        pdev = pci_get_slot(zbus->bus, zdev->devfn);
        if (pdev) {
                if (set_error)
                        pdev->error_state = pci_channel_io_perm_failure;
                if (pdev->is_virtfn) {
                        zpci_iov_remove_virtfn(pdev, zdev->vfn);
                        /* balance pci_get_slot */
                        pci_dev_put(pdev);
                        return;
                }
                pci_stop_and_remove_bus_device_locked(pdev);
                /* balance pci_get_slot */
                pci_dev_put(pdev);
        }
}

/* zpci_bus_scan_bus - Scan all configured zPCI functions on the bus
 * @zbus: the zbus to be scanned
 *
 * Enables and scans all PCI functions on the bus making them available to the
 * common PCI code. If a PCI function fails to be initialized an error will be
 * returned but attempts will still be made for all other functions on the bus.
 *
 * Return: 0 on success, an error value otherwise
 */
int zpci_bus_scan_bus(struct zpci_bus *zbus)
{
        struct zpci_dev *zdev;
        int devfn, rc, ret = 0;

        for (devfn = 0; devfn < ZPCI_FUNCTIONS_PER_BUS; devfn++) {
                zdev = zbus->function[devfn];
                if (zdev && zdev->state == ZPCI_FN_STATE_CONFIGURED) {
                        rc = zpci_bus_prepare_device(zdev);
                        if (rc)
                                ret = -EIO;
                }
        }

        pci_lock_rescan_remove();
        pci_scan_child_bus(zbus->bus);
        pci_bus_add_devices(zbus->bus);
        pci_unlock_rescan_remove();

        return ret;
}

static bool zpci_bus_is_multifunction_root(struct zpci_dev *zdev)
{
        return !s390_pci_no_rid && zdev->rid_available &&
                !zdev->vfn;
}

/* zpci_bus_create_pci_bus - Create the PCI bus associated with this zbus
 * @zbus: the zbus holding the zdevices
 * @fr: PCI root function that will determine the bus's domain, and bus speed
 * @ops: the pci operations
 *
 * The PCI function @fr determines the domain (its UID), multifunction property
 * and maximum bus speed of the entire bus.
 *
 * Return: 0 on success, an error code otherwise
 */
static int zpci_bus_create_pci_bus(struct zpci_bus *zbus, struct zpci_dev *fr, struct pci_ops *ops)
{
        struct pci_bus *bus;
        int domain;

        domain = zpci_alloc_domain((u16)fr->uid);
        if (domain < 0)
                return domain;

        zbus->domain_nr = domain;
        zbus->multifunction = zpci_bus_is_multifunction_root(fr);
        zbus->max_bus_speed = fr->max_bus_speed;

        if (zpci_create_parent_msi_domain(zbus))
                goto out_free_domain;

        /*
         * Note that the zbus->resources are taken over and zbus->resources
         * is empty after a successful call
         */
        bus = pci_create_root_bus(NULL, ZPCI_BUS_NR, ops, zbus, &zbus->resources);
        if (!bus)
                goto out_remove_msi_domain;

        zbus->bus = bus;
        dev_set_msi_domain(&zbus->bus->dev, zbus->msi_parent_domain);

        return 0;

out_remove_msi_domain:
        zpci_remove_parent_msi_domain(zbus);
out_free_domain:
        zpci_free_domain(zbus->domain_nr);
        return -ENOMEM;
}

/**
 * zpci_bus_release - Un-initialize resources associated with the zbus and
 *                    free memory
 * @kref:       refcount * that is part of struct zpci_bus
 *
 * MUST be called with `zbus_list_lock` held, but the lock is released during
 * run of the function.
 */
static inline void zpci_bus_release(struct kref *kref)
        __releases(&zbus_list_lock)
{
        struct zpci_bus *zbus = container_of(kref, struct zpci_bus, kref);

        lockdep_assert_held(&zbus_list_lock);

        list_del(&zbus->bus_next);
        mutex_unlock(&zbus_list_lock);

        /*
         * At this point no-one should see this object, or be able to get a new
         * reference to it.
         */

        if (zbus->bus) {
                pci_lock_rescan_remove();
                pci_stop_root_bus(zbus->bus);

                zpci_free_domain(zbus->domain_nr);
                pci_free_resource_list(&zbus->resources);

                pci_remove_root_bus(zbus->bus);
                pci_unlock_rescan_remove();
        }

        zpci_remove_parent_msi_domain(zbus);
        kfree(zbus);
}

static inline void __zpci_bus_get(struct zpci_bus *zbus)
{
        lockdep_assert_held(&zbus_list_lock);
        kref_get(&zbus->kref);
}

static inline void zpci_bus_put(struct zpci_bus *zbus)
{
        kref_put_mutex(&zbus->kref, zpci_bus_release, &zbus_list_lock);
}

static struct zpci_bus *zpci_bus_get(int topo, bool topo_is_tid)
{
        struct zpci_bus *zbus;

        mutex_lock(&zbus_list_lock);
        list_for_each_entry(zbus, &zbus_list, bus_next) {
                if (!zbus->multifunction)
                        continue;
                if (topo_is_tid == zbus->topo_is_tid && topo == zbus->topo) {
                        __zpci_bus_get(zbus);
                        goto out_unlock;
                }
        }
        zbus = NULL;
out_unlock:
        mutex_unlock(&zbus_list_lock);
        return zbus;
}

/**
 * zpci_bus_get_next - get the next zbus object from given position in the list
 * @pos:        current position/cursor in the global zbus list
 *
 * Acquires and releases references as the cursor iterates (might also free/
 * release the cursor). Is tolerant of concurrent operations on the list.
 *
 * To begin the iteration, set *@pos to %NULL before calling the function.
 *
 * *@pos is set to %NULL in cases where either the list is empty, or *@pos is
 * the last element in the list.
 *
 * Context: Process context. May sleep.
 */
void zpci_bus_get_next(struct zpci_bus **pos)
{
        struct zpci_bus *curp = *pos, *next = NULL;

        mutex_lock(&zbus_list_lock);
        if (curp)
                next = list_next_entry(curp, bus_next);
        else
                next = list_first_entry(&zbus_list, typeof(*curp), bus_next);

        if (list_entry_is_head(next, &zbus_list, bus_next))
                next = NULL;

        if (next)
                __zpci_bus_get(next);

        *pos = next;
        mutex_unlock(&zbus_list_lock);

        /* zpci_bus_put() might drop refcount to 0 and locks zbus_list_lock */
        if (curp)
                zpci_bus_put(curp);
}

static struct zpci_bus *zpci_bus_alloc(int topo, bool topo_is_tid)
{
        struct zpci_bus *zbus;

        zbus = kzalloc_obj(*zbus);
        if (!zbus)
                return NULL;

        zbus->topo = topo;
        zbus->topo_is_tid = topo_is_tid;
        INIT_LIST_HEAD(&zbus->bus_next);

        kref_init(&zbus->kref);
        INIT_LIST_HEAD(&zbus->resources);

        zbus->bus_resource.start = 0;
        zbus->bus_resource.end = ZPCI_BUS_NR;
        zbus->bus_resource.flags = IORESOURCE_BUS;
        pci_add_resource(&zbus->resources, &zbus->bus_resource);

        mutex_lock(&zbus_list_lock);
        list_add_tail(&zbus->bus_next, &zbus_list);
        mutex_unlock(&zbus_list_lock);

        return zbus;
}

static void pci_dma_range_setup(struct pci_dev *pdev)
{
        struct zpci_dev *zdev = to_zpci(pdev);
        u64 aligned_end, size;
        dma_addr_t dma_start;
        int ret;

        dma_start = PAGE_ALIGN(zdev->start_dma);
        aligned_end = PAGE_ALIGN_DOWN(zdev->end_dma + 1);
        if (aligned_end >= dma_start)
                size = aligned_end - dma_start;
        else
                size = 0;
        WARN_ON_ONCE(size == 0);

        ret = dma_direct_set_offset(&pdev->dev, 0, dma_start, size);
        if (ret)
                pr_err("Failed to allocate DMA range map for %s\n", pci_name(pdev));
}

void pcibios_bus_add_device(struct pci_dev *pdev)
{
        struct zpci_dev *zdev = to_zpci(pdev);

        pci_dma_range_setup(pdev);

        /*
         * With pdev->no_vf_scan the common PCI probing code does not
         * perform PF/VF linking.
         */
        if (zdev->vfn) {
                zpci_iov_setup_virtfn(zdev->zbus, pdev, zdev->vfn);
                pdev->no_command_memory = 1;
        }
}

static int zpci_bus_add_device(struct zpci_bus *zbus, struct zpci_dev *zdev)
{
        int rc = -EINVAL;

        if (zbus->multifunction) {
                if (!zdev->rid_available) {
                        WARN_ONCE(1, "rid_available not set for multifunction\n");
                        return rc;
                }
                zdev->devfn = zdev->rid & ZPCI_RID_MASK_DEVFN;
        }

        if (zbus->function[zdev->devfn]) {
                pr_err("devfn %04x is already assigned\n", zdev->devfn);
                return rc;
        }
        zdev->zbus = zbus;
        zbus->function[zdev->devfn] = zdev;
        zpci_nb_devices++;

        rc = zpci_init_slot(zdev);
        if (rc)
                goto error;
        zdev->has_hp_slot = 1;

        return 0;

error:
        zbus->function[zdev->devfn] = NULL;
        zdev->zbus = NULL;
        zpci_nb_devices--;
        return rc;
}

static bool zpci_bus_is_isolated_vf(struct zpci_bus *zbus, struct zpci_dev *zdev)
{
        struct pci_dev *pdev;

        if (!zdev->vfn)
                return false;

        pdev = zpci_iov_find_parent_pf(zbus, zdev);
        if (!pdev)
                return true;
        pci_dev_put(pdev);
        return false;
}

int zpci_bus_device_register(struct zpci_dev *zdev, struct pci_ops *ops)
{
        bool topo_is_tid = zdev->tid_avail;
        struct zpci_bus *zbus = NULL;
        int topo, rc = -EBADF;

        if (zpci_nb_devices == ZPCI_NR_DEVICES) {
                pr_warn("Adding PCI function %08x failed because the configured limit of %d is reached\n",
                        zdev->fid, ZPCI_NR_DEVICES);
                return -ENOSPC;
        }

        topo = topo_is_tid ? zdev->tid : zdev->pchid;
        zbus = zpci_bus_get(topo, topo_is_tid);
        /*
         * An isolated VF gets its own domain/bus even if there exists
         * a matching domain/bus already
         */
        if (zbus && zpci_bus_is_isolated_vf(zbus, zdev)) {
                zpci_bus_put(zbus);
                zbus = NULL;
        }

        if (!zbus) {
                zbus = zpci_bus_alloc(topo, topo_is_tid);
                if (!zbus)
                        return -ENOMEM;
        }

        if (!zbus->bus) {
                /* The UID of the first PCI function registered with a zpci_bus
                 * is used as the domain number for that bus. Currently there
                 * is exactly one zpci_bus per domain.
                 */
                rc = zpci_bus_create_pci_bus(zbus, zdev, ops);
                if (rc)
                        goto error;
        }

        rc = zpci_bus_add_device(zbus, zdev);
        if (rc)
                goto error;

        return 0;

error:
        pr_err("Adding PCI function %08x failed\n", zdev->fid);
        zpci_bus_put(zbus);
        return rc;
}

void zpci_bus_device_unregister(struct zpci_dev *zdev)
{
        struct zpci_bus *zbus = zdev->zbus;

        zpci_nb_devices--;
        zbus->function[zdev->devfn] = NULL;
        zpci_bus_put(zbus);
}