/*
 * PCI Hotplug Driver for PowerPC PowerNV platform.
 *
 * Copyright Gavin Shan, IBM Corporation 2016.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/libfdt.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/pci_hotplug.h>

#include <asm/opal.h>
#include <asm/pnv-pci.h>
#include <asm/ppc-pci.h>

#define DRIVER_VERSION  "0.1"
#define DRIVER_AUTHOR   "Gavin Shan, IBM Corporation"
#define DRIVER_DESC     "PowerPC PowerNV PCI Hotplug Driver"

static LIST_HEAD(pnv_php_slot_list);
static DEFINE_SPINLOCK(pnv_php_lock);

static void pnv_php_register(struct device_node *dn);
static void pnv_php_unregister_one(struct device_node *dn);
static void pnv_php_unregister(struct device_node *dn);

static void pnv_php_free_slot(struct kref *kref)
{
        struct pnv_php_slot *php_slot = container_of(kref,
                                        struct pnv_php_slot, kref);

        WARN_ON(!list_empty(&php_slot->children));
        kfree(php_slot->name);
        kfree(php_slot);
}

static inline void pnv_php_put_slot(struct pnv_php_slot *php_slot)
{

        if (WARN_ON(!php_slot))
                return;

        kref_put(&php_slot->kref, pnv_php_free_slot);
}

static struct pnv_php_slot *pnv_php_match(struct device_node *dn,
                                          struct pnv_php_slot *php_slot)
{
        struct pnv_php_slot *target, *tmp;

        if (php_slot->dn == dn) {
                kref_get(&php_slot->kref);
                return php_slot;
        }

        list_for_each_entry(tmp, &php_slot->children, link) {
                target = pnv_php_match(dn, tmp);
                if (target)
                        return target;
        }

        return NULL;
}

struct pnv_php_slot *pnv_php_find_slot(struct device_node *dn)
{
        struct pnv_php_slot *php_slot, *tmp;
        unsigned long flags;

        spin_lock_irqsave(&pnv_php_lock, flags);
        list_for_each_entry(tmp, &pnv_php_slot_list, link) {
                php_slot = pnv_php_match(dn, tmp);
                if (php_slot) {
                        spin_unlock_irqrestore(&pnv_php_lock, flags);
                        return php_slot;
                }
        }
        spin_unlock_irqrestore(&pnv_php_lock, flags);

        return NULL;
}
EXPORT_SYMBOL_GPL(pnv_php_find_slot);

/*
 * Remove pdn for all children of the indicated device node.
 * The function should remove pdn in a depth-first manner.
 */
static void pnv_php_rmv_pdns(struct device_node *dn)
{
        struct device_node *child;

        for_each_child_of_node(dn, child) {
                pnv_php_rmv_pdns(child);

                pci_remove_device_node_info(child);
        }
}

/*
 * Detach all child nodes of the indicated device nodes. The
 * function should handle device nodes in depth-first manner.
 *
 * We should not invoke of_node_release() as the memory for
 * individual device node is part of large memory block. The
 * large block is allocated from memblock (system bootup) or
 * kmalloc() when unflattening the device tree by OF changeset.
 * We can not free the large block allocated from memblock. For
 * later case, it should be released at once.
 */
static void pnv_php_detach_device_nodes(struct device_node *parent)
{
        struct device_node *dn;
        int refcount;

        for_each_child_of_node(parent, dn) {
                pnv_php_detach_device_nodes(dn);

                of_node_put(dn);
                refcount = atomic_read(&dn->kobj.kref.refcount);
                if (unlikely(refcount != 1))
                        pr_warn("Invalid refcount %d on <%s>\n",
                                refcount, of_node_full_name(dn));

                of_detach_node(dn);
        }
}

static void pnv_php_rmv_devtree(struct pnv_php_slot *php_slot)
{
        pnv_php_rmv_pdns(php_slot->dn);

        /*
         * Decrease the refcount if the device nodes were created
         * through OF changeset before detaching them.
         */
        if (php_slot->fdt)
                of_changeset_destroy(&php_slot->ocs);
        pnv_php_detach_device_nodes(php_slot->dn);

        if (php_slot->fdt) {
                kfree(php_slot->dt);
                kfree(php_slot->fdt);
                php_slot->dt        = NULL;
                php_slot->dn->child = NULL;
                php_slot->fdt       = NULL;
        }
}

/*
 * As the nodes in OF changeset are applied in reverse order, we
 * need revert the nodes in advance so that we have correct node
 * order after the changeset is applied.
 */
static void pnv_php_reverse_nodes(struct device_node *parent)
{
        struct device_node *child, *next;

        /* In-depth first */
        for_each_child_of_node(parent, child)
                pnv_php_reverse_nodes(child);

        /* Reverse the nodes in the child list */
        child = parent->child;
        parent->child = NULL;
        while (child) {
                next = child->sibling;

                child->sibling = parent->child;
                parent->child = child;
                child = next;
        }
}

static int pnv_php_populate_changeset(struct of_changeset *ocs,
                                      struct device_node *dn)
{
        struct device_node *child;
        int ret = 0;

        for_each_child_of_node(dn, child) {
                ret = of_changeset_attach_node(ocs, child);
                if (unlikely(ret))
                        break;

                ret = pnv_php_populate_changeset(ocs, child);
                if (unlikely(ret))
                        break;
        }

        return ret;
}

static void *pnv_php_add_one_pdn(struct device_node *dn, void *data)
{
        struct pci_controller *hose = (struct pci_controller *)data;
        struct pci_dn *pdn;

        pdn = pci_add_device_node_info(hose, dn);
        if (unlikely(!pdn))
                return ERR_PTR(-ENOMEM);

        return NULL;
}

static void pnv_php_add_pdns(struct pnv_php_slot *slot)
{
        struct pci_controller *hose = pci_bus_to_host(slot->bus);

        pci_traverse_device_nodes(slot->dn, pnv_php_add_one_pdn, hose);
}

static int pnv_php_add_devtree(struct pnv_php_slot *php_slot)
{
        void *fdt, *fdt1, *dt;
        int ret;

        /* We don't know the FDT blob size. We try to get it through
         * maximal memory chunk and then copy it to another chunk that
         * fits the real size.
         */
        fdt1 = kzalloc(0x10000, GFP_KERNEL);
        if (unlikely(!fdt1)) {
                ret = -ENOMEM;
                dev_warn(&php_slot->pdev->dev, "Cannot alloc FDT blob\n");
                goto out;
        }

        ret = pnv_pci_get_device_tree(php_slot->dn->phandle, fdt1, 0x10000);
        if (unlikely(ret)) {
                dev_warn(&php_slot->pdev->dev, "Error %d getting FDT blob\n",
                         ret);
                goto free_fdt1;
        }

        fdt = kzalloc(fdt_totalsize(fdt1), GFP_KERNEL);
        if (unlikely(!fdt)) {
                ret = -ENOMEM;
                dev_warn(&php_slot->pdev->dev, "Cannot %d bytes memory\n",
                         fdt_totalsize(fdt1));
                goto free_fdt1;
        }

        /* Unflatten device tree blob */
        memcpy(fdt, fdt1, fdt_totalsize(fdt1));
        dt = of_fdt_unflatten_tree(fdt, php_slot->dn, NULL);
        if (unlikely(!dt)) {
                ret = -EINVAL;
                dev_warn(&php_slot->pdev->dev, "Cannot unflatten FDT\n");
                goto free_fdt;
        }

        /* Initialize and apply the changeset */
        of_changeset_init(&php_slot->ocs);
        pnv_php_reverse_nodes(php_slot->dn);
        ret = pnv_php_populate_changeset(&php_slot->ocs, php_slot->dn);
        if (unlikely(ret)) {
                pnv_php_reverse_nodes(php_slot->dn);
                dev_warn(&php_slot->pdev->dev, "Error %d populating changeset\n",
                         ret);
                goto free_dt;
        }

        php_slot->dn->child = NULL;
        ret = of_changeset_apply(&php_slot->ocs);
        if (unlikely(ret)) {
                dev_warn(&php_slot->pdev->dev, "Error %d applying changeset\n",
                         ret);
                goto destroy_changeset;
        }

        /* Add device node firmware data */
        pnv_php_add_pdns(php_slot);
        php_slot->fdt = fdt;
        php_slot->dt  = dt;
        kfree(fdt1);
        goto out;

destroy_changeset:
        of_changeset_destroy(&php_slot->ocs);
free_dt:
        kfree(dt);
        php_slot->dn->child = NULL;
free_fdt:
        kfree(fdt);
free_fdt1:
        kfree(fdt1);
out:
        return ret;
}

int pnv_php_set_slot_power_state(struct hotplug_slot *slot,
                                 uint8_t state)
{
        struct pnv_php_slot *php_slot = slot->private;
        struct opal_msg msg;
        int ret;

        ret = pnv_pci_set_power_state(php_slot->id, state, &msg);
        if (likely(ret > 0)) {
                if (be64_to_cpu(msg.params[1]) != php_slot->dn->phandle ||
                    be64_to_cpu(msg.params[2]) != state                 ||
                    be64_to_cpu(msg.params[3]) != OPAL_SUCCESS) {
                        dev_warn(&php_slot->pdev->dev, "Wrong msg (%lld, %lld, %lld)\n",
                                 be64_to_cpu(msg.params[1]),
                                 be64_to_cpu(msg.params[2]),
                                 be64_to_cpu(msg.params[3]));
                        return -ENOMSG;
                }
        } else if (unlikely(ret < 0)) {
                dev_warn(&php_slot->pdev->dev, "Error %d powering %s\n",
                         ret, (state == OPAL_PCI_SLOT_POWER_ON) ? "on" : "off");
                return ret;
        }

        if (state == OPAL_PCI_SLOT_POWER_OFF || state == OPAL_PCI_SLOT_OFFLINE)
                pnv_php_rmv_devtree(php_slot);
        else
                ret = pnv_php_add_devtree(php_slot);

        return ret;
}
EXPORT_SYMBOL_GPL(pnv_php_set_slot_power_state);

static int pnv_php_get_power_state(struct hotplug_slot *slot, u8 *state)
{
        struct pnv_php_slot *php_slot = slot->private;
        uint8_t power_state = OPAL_PCI_SLOT_POWER_ON;
        int ret;

        /*
         * Retrieve power status from firmware. If we fail
         * getting that, the power status fails back to
         * be on.
         */
        ret = pnv_pci_get_power_state(php_slot->id, &power_state);
        if (unlikely(ret)) {
                dev_warn(&php_slot->pdev->dev, "Error %d getting power status\n",
                         ret);
        } else {
                *state = power_state;
                slot->info->power_status = power_state;
        }

        return 0;
}

static int pnv_php_get_adapter_state(struct hotplug_slot *slot, u8 *state)
{
        struct pnv_php_slot *php_slot = slot->private;
        uint8_t presence = OPAL_PCI_SLOT_EMPTY;
        int ret;

        /*
         * Retrieve presence status from firmware. If we can't
         * get that, it will fail back to be empty.
         */
        ret = pnv_pci_get_presence_state(php_slot->id, &presence);
        if (likely(ret >= 0)) {
                *state = presence;
                slot->info->adapter_status = presence;
                ret = 0;
        } else {
                dev_warn(&php_slot->pdev->dev, "Error %d getting presence\n",
                         ret);
        }

        return ret;
}

static int pnv_php_set_attention_state(struct hotplug_slot *slot, u8 state)
{
        /* FIXME: Make it real once firmware supports it */
        slot->info->attention_status = state;

        return 0;
}

static int pnv_php_enable(struct pnv_php_slot *php_slot, bool rescan)
{
        struct hotplug_slot *slot = &php_slot->slot;
        uint8_t presence = OPAL_PCI_SLOT_EMPTY;
        uint8_t power_status = OPAL_PCI_SLOT_POWER_ON;
        int ret;

        /* Check if the slot has been configured */
        if (php_slot->state != PNV_PHP_STATE_REGISTERED)
                return 0;

        /* Retrieve slot presence status */
        ret = pnv_php_get_adapter_state(slot, &presence);
        if (unlikely(ret))
                return ret;

        /* Proceed if there have nothing behind the slot */
        if (presence == OPAL_PCI_SLOT_EMPTY)
                goto scan;

        /*
         * If the power supply to the slot is off, we can't detect
         * adapter presence state. That means we have to turn the
         * slot on before going to probe slot's presence state.
         *
         * On the first time, we don't change the power status to
         * boost system boot with assumption that the firmware
         * supplies consistent slot power status: empty slot always
         * has its power off and non-empty slot has its power on.
         */
        if (!php_slot->power_state_check) {
                php_slot->power_state_check = true;

                ret = pnv_php_get_power_state(slot, &power_status);
                if (unlikely(ret))
                        return ret;

                if (power_status != OPAL_PCI_SLOT_POWER_ON)
                        return 0;
        }

        /* Check the power status. Scan the slot if it is already on */
        ret = pnv_php_get_power_state(slot, &power_status);
        if (unlikely(ret))
                return ret;

        if (power_status == OPAL_PCI_SLOT_POWER_ON)
                goto scan;

        /* Power is off, turn it on and then scan the slot */
        ret = pnv_php_set_slot_power_state(slot, OPAL_PCI_SLOT_POWER_ON);
        if (unlikely(ret))
                return ret;

scan:
        if (presence == OPAL_PCI_SLOT_PRESENT) {
                if (rescan) {
                        pci_lock_rescan_remove();
                        pci_hp_add_devices(php_slot->bus);
                        pci_unlock_rescan_remove();
                }

                /* Rescan for child hotpluggable slots */
                php_slot->state = PNV_PHP_STATE_POPULATED;
                if (rescan)
                        pnv_php_register(php_slot->dn);
        } else {
                php_slot->state = PNV_PHP_STATE_POPULATED;
        }

        return 0;
}

static int pnv_php_enable_slot(struct hotplug_slot *slot)
{
        struct pnv_php_slot *php_slot = container_of(slot,
                                                     struct pnv_php_slot, slot);

        return pnv_php_enable(php_slot, true);
}

static int pnv_php_disable_slot(struct hotplug_slot *slot)
{
        struct pnv_php_slot *php_slot = slot->private;
        int ret;

        if (php_slot->state != PNV_PHP_STATE_POPULATED)
                return 0;

        /* Remove all devices behind the slot */
        pci_lock_rescan_remove();
        pci_hp_remove_devices(php_slot->bus);
        pci_unlock_rescan_remove();

        /* Detach the child hotpluggable slots */
        pnv_php_unregister(php_slot->dn);

        /* Notify firmware and remove device nodes */
        ret = pnv_php_set_slot_power_state(slot, OPAL_PCI_SLOT_POWER_OFF);

        php_slot->state = PNV_PHP_STATE_REGISTERED;
        return ret;
}

static struct hotplug_slot_ops php_slot_ops = {
        .get_power_status       = pnv_php_get_power_state,
        .get_adapter_status     = pnv_php_get_adapter_state,
        .set_attention_status   = pnv_php_set_attention_state,
        .enable_slot            = pnv_php_enable_slot,
        .disable_slot           = pnv_php_disable_slot,
};

static void pnv_php_release(struct hotplug_slot *slot)
{
        struct pnv_php_slot *php_slot = slot->private;
        unsigned long flags;

        /* Remove from global or child list */
        spin_lock_irqsave(&pnv_php_lock, flags);
        list_del(&php_slot->link);
        spin_unlock_irqrestore(&pnv_php_lock, flags);

        /* Detach from parent */
        pnv_php_put_slot(php_slot);
        pnv_php_put_slot(php_slot->parent);
}

static struct pnv_php_slot *pnv_php_alloc_slot(struct device_node *dn)
{
        struct pnv_php_slot *php_slot;
        struct pci_bus *bus;
        const char *label;
        uint64_t id;

        label = of_get_property(dn, "ibm,slot-label", NULL);
        if (unlikely(!label))
                return NULL;

        if (pnv_pci_get_slot_id(dn, &id))
                return NULL;

        bus = pci_find_bus_by_node(dn);
        if (unlikely(!bus))
                return NULL;

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

        php_slot->name = kstrdup(label, GFP_KERNEL);
        if (unlikely(!php_slot->name)) {
                kfree(php_slot);
                return NULL;
        }

        if (likely(dn->child && PCI_DN(dn->child)))
                php_slot->slot_no = PCI_SLOT(PCI_DN(dn->child)->devfn);
        else
                php_slot->slot_no = -1;   /* Placeholder slot */

        kref_init(&php_slot->kref);
        php_slot->state                 = PNV_PHP_STATE_INITIALIZED;
        php_slot->dn                    = dn;
        php_slot->pdev                  = bus->self;
        php_slot->bus                   = bus;
        php_slot->id                    = id;
        php_slot->power_state_check     = false;
        php_slot->slot.ops              = &php_slot_ops;
        php_slot->slot.info             = &php_slot->slot_info;
        php_slot->slot.release          = pnv_php_release;
        php_slot->slot.private          = php_slot;

        INIT_LIST_HEAD(&php_slot->children);
        INIT_LIST_HEAD(&php_slot->link);

        return php_slot;
}

static int pnv_php_register_slot(struct pnv_php_slot *php_slot)
{
        struct pnv_php_slot *parent;
        struct device_node *dn = php_slot->dn;
        unsigned long flags;
        int ret;

        /* Check if the slot is registered or not */
        parent = pnv_php_find_slot(php_slot->dn);
        if (unlikely(parent)) {
                pnv_php_put_slot(parent);
                return -EEXIST;
        }

        /* Register PCI slot */
        ret = pci_hp_register(&php_slot->slot, php_slot->bus,
                              php_slot->slot_no, php_slot->name);
        if (unlikely(ret)) {
                dev_warn(&php_slot->pdev->dev, "Error %d registering slot\n",
                         ret);
                return ret;
        }

        /* Attach to the parent's child list or global list */
        while ((dn = of_get_parent(dn))) {
                if (!PCI_DN(dn)) {
                        of_node_put(dn);
                        break;
                }

                parent = pnv_php_find_slot(dn);
                if (parent) {
                        of_node_put(dn);
                        break;
                }

                of_node_put(dn);
        }

        spin_lock_irqsave(&pnv_php_lock, flags);
        php_slot->parent = parent;
        if (parent)
                list_add_tail(&php_slot->link, &parent->children);
        else
                list_add_tail(&php_slot->link, &pnv_php_slot_list);
        spin_unlock_irqrestore(&pnv_php_lock, flags);

        php_slot->state = PNV_PHP_STATE_REGISTERED;
        return 0;
}

static int pnv_php_register_one(struct device_node *dn)
{
        struct pnv_php_slot *php_slot;
        const __be32 *prop32;
        int ret;

        /* Check if it's hotpluggable slot */
        prop32 = of_get_property(dn, "ibm,slot-pluggable", NULL);
        if (!prop32 || !of_read_number(prop32, 1))
                return -ENXIO;

        prop32 = of_get_property(dn, "ibm,reset-by-firmware", NULL);
        if (!prop32 || !of_read_number(prop32, 1))
                return -ENXIO;

        php_slot = pnv_php_alloc_slot(dn);
        if (unlikely(!php_slot))
                return -ENODEV;

        ret = pnv_php_register_slot(php_slot);
        if (unlikely(ret))
                goto free_slot;

        ret = pnv_php_enable(php_slot, false);
        if (unlikely(ret))
                goto unregister_slot;

        return 0;

unregister_slot:
        pnv_php_unregister_one(php_slot->dn);
free_slot:
        pnv_php_put_slot(php_slot);
        return ret;
}

static void pnv_php_register(struct device_node *dn)
{
        struct device_node *child;

        /*
         * The parent slots should be registered before their
         * child slots.
         */
        for_each_child_of_node(dn, child) {
                pnv_php_register_one(child);
                pnv_php_register(child);
        }
}

static void pnv_php_unregister_one(struct device_node *dn)
{
        struct pnv_php_slot *php_slot;

        php_slot = pnv_php_find_slot(dn);
        if (!php_slot)
                return;

        php_slot->state = PNV_PHP_STATE_OFFLINE;
        pnv_php_put_slot(php_slot);
        pci_hp_deregister(&php_slot->slot);
}

static void pnv_php_unregister(struct device_node *dn)
{
        struct device_node *child;

        /* The child slots should go before their parent slots */
        for_each_child_of_node(dn, child) {
                pnv_php_unregister(child);
                pnv_php_unregister_one(child);
        }
}

static int __init pnv_php_init(void)
{
        struct device_node *dn;

        pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
        for_each_compatible_node(dn, NULL, "ibm,ioda2-phb")
                pnv_php_register(dn);

        return 0;
}

static void __exit pnv_php_exit(void)
{
        struct device_node *dn;

        for_each_compatible_node(dn, NULL, "ibm,ioda2-phb")
                pnv_php_unregister(dn);
}

module_init(pnv_php_init);
module_exit(pnv_php_exit);

MODULE_VERSION(DRIVER_VERSION);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);