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

#define KMSG_COMPONENT "zpci"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/delay.h>
#include <linux/seq_file.h>
#include <linux/jump_label.h>
#include <linux/pci.h>
#include <linux/printk.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)
{
        struct resource_entry *window, *n;
        struct resource *res;
        int rc;

        if (!zdev_enabled(zdev)) {
                rc = zpci_enable_device(zdev);
                if (rc)
                        return rc;
                rc = zpci_dma_init_device(zdev);
                if (rc) {
                        zpci_disable_device(zdev);
                        return rc;
                }
        }

        if (!zdev->has_resources) {
                zpci_setup_bus_resources(zdev, &zdev->zbus->resources);
                resource_list_for_each_entry_safe(window, n, &zdev->zbus->resources) {
                        res = window->res;
                        pci_bus_add_resource(zdev->zbus->bus, res, 0);
                }
        }

        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_bus_add_device(pdev);
        pci_lock_rescan_remove();
        pci_bus_add_devices(zdev->zbus->bus);
        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 there is no function 0 on the zbus nothing is scanned. If
 * a function does not have a slot yet because it was added to the zbus before
 * function 0 the slot is created. 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;

        if (!zbus->function[0])
                return 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;
}

/* zpci_bus_scan_busses - Scan all registered busses
 *
 * Scan all available zbusses
 *
 */
void zpci_bus_scan_busses(void)
{
        struct zpci_bus *zbus = NULL;

        mutex_lock(&zbus_list_lock);
        list_for_each_entry(zbus, &zbus_list, bus_next) {
                zpci_bus_scan_bus(zbus);
                cond_resched();
        }
        mutex_unlock(&zbus_list_lock);
}

/* zpci_bus_create_pci_bus - Create the PCI bus associated with this zbus
 * @zbus: the zbus holding the zdevices
 * @f0: function 0 of the bus
 * @ops: the pci operations
 *
 * Function zero is taken as a parameter as this is used to determine the
 * domain, 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 *f0, struct pci_ops *ops)
{
        struct pci_bus *bus;
        int domain;

        domain = zpci_alloc_domain((u16)f0->uid);
        if (domain < 0)
                return domain;

        zbus->domain_nr = domain;
        zbus->multifunction = f0->rid_available;
        zbus->max_bus_speed = f0->max_bus_speed;

        /*
         * 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) {
                zpci_free_domain(zbus->domain_nr);
                return -EFAULT;
        }

        zbus->bus = bus;
        pci_bus_add_devices(bus);

        return 0;
}

static void zpci_bus_release(struct kref *kref)
{
        struct zpci_bus *zbus = container_of(kref, struct zpci_bus, kref);

        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();
        }

        mutex_lock(&zbus_list_lock);
        list_del(&zbus->bus_next);
        mutex_unlock(&zbus_list_lock);
        kfree(zbus);
}

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

static struct zpci_bus *zpci_bus_get(int pchid)
{
        struct zpci_bus *zbus;

        mutex_lock(&zbus_list_lock);
        list_for_each_entry(zbus, &zbus_list, bus_next) {
                if (pchid == zbus->pchid) {
                        kref_get(&zbus->kref);
                        goto out_unlock;
                }
        }
        zbus = NULL;
out_unlock:
        mutex_unlock(&zbus_list_lock);
        return zbus;
}

static struct zpci_bus *zpci_bus_alloc(int pchid)
{
        struct zpci_bus *zbus;

        zbus = kzalloc(sizeof(*zbus), GFP_KERNEL);
        if (!zbus)
                return NULL;

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

        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);

        return zbus;
}

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

/* zpci_bus_create_hotplug_slots - Add hotplug slot(s) for device added to bus
 * @zdev: the zPCI device that was newly added
 *
 * Add the hotplug slot(s) for the newly added PCI function. Normally this is
 * simply the slot for the function itself. If however we are adding the
 * function 0 on a zbus, it might be that we already registered functions on
 * that zbus but could not create their hotplug slots yet so add those now too.
 *
 * Return: 0 on success, an error code otherwise
 */
static int zpci_bus_create_hotplug_slots(struct zpci_dev *zdev)
{
        struct zpci_bus *zbus = zdev->zbus;
        int devfn, rc = 0;

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

        if (zdev->devfn == 0 && zbus->multifunction) {
                /* Now that function 0 is there we can finally create the
                 * hotplug slots for those functions with devfn != 0 that have
                 * been parked in zbus->function[] waiting for us to be able to
                 * create the PCI bus.
                 */
                for  (devfn = 1; devfn < ZPCI_FUNCTIONS_PER_BUS; devfn++) {
                        zdev = zbus->function[devfn];
                        if (zdev && !zdev->has_hp_slot) {
                                rc = zpci_init_slot(zdev);
                                if (rc)
                                        return rc;
                                zdev->has_hp_slot = 1;
                        }
                }

        }

        return rc;
}

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

        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++;

        if (zbus->bus) {
                if (zbus->multifunction && !zdev->rid_available) {
                        WARN_ONCE(1, "rid_available not set for multifunction\n");
                        goto error;
                }

                zpci_bus_create_hotplug_slots(zdev);
        } else {
                /* Hotplug slot will be created once function 0 appears */
                zbus->multifunction = 1;
        }

        return 0;

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

int zpci_bus_device_register(struct zpci_dev *zdev, struct pci_ops *ops)
{
        struct zpci_bus *zbus = NULL;
        int 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;
        }

        if (zdev->devfn >= ZPCI_FUNCTIONS_PER_BUS)
                return -EINVAL;

        if (!s390_pci_no_rid && zdev->rid_available)
                zbus = zpci_bus_get(zdev->pchid);

        if (!zbus) {
                zbus = zpci_bus_alloc(zdev->pchid);
                if (!zbus)
                        return -ENOMEM;
        }

        if (zdev->devfn == 0) {
                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);
}