path: root/drivers/pci/hotplug/acpiphp_glue.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * ACPI PCI HotPlug glue functions to ACPI CA subsystem
 *
 * Copyright (C) 2002,2003 Takayoshi Kochi (t-kochi@bq.jp.nec.com)
 * Copyright (C) 2002 Hiroshi Aono (h-aono@ap.jp.nec.com)
 * Copyright (C) 2002,2003 NEC Corporation
 * Copyright (C) 2003-2005 Matthew Wilcox (willy@infradead.org)
 * Copyright (C) 2003-2005 Hewlett Packard
 * Copyright (C) 2005 Rajesh Shah (rajesh.shah@intel.com)
 * Copyright (C) 2005 Intel Corporation
 *
 * All rights reserved.
 *
 * Send feedback to <kristen.c.accardi@intel.com>
 *
 */

/*
 * Lifetime rules for pci_dev:
 *  - The one in acpiphp_bridge has its refcount elevated by pci_get_slot()
 *    when the bridge is scanned and it loses a refcount when the bridge
 *    is removed.
 *  - When a P2P bridge is present, we elevate the refcount on the subordinate
 *    bus. It loses the refcount when the the driver unloads.
 */

#define pr_fmt(fmt) "acpiphp_glue: " fmt

#include <linux/module.h>

#include <linux/kernel.h>
#include <linux/pci.h>
#include <linux/pci_hotplug.h>
#include <linux/pci-acpi.h>
#include <linux/pm_runtime.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/acpi.h>

#include "../pci.h"
#include "acpiphp.h"

static LIST_HEAD(bridge_list);
static DEFINE_MUTEX(bridge_mutex);

static int acpiphp_hotplug_notify(struct acpi_device *adev, u32 type);
static void acpiphp_post_dock_fixup(struct acpi_device *adev);
static void acpiphp_sanitize_bus(struct pci_bus *bus);
static void hotplug_event(u32 type, struct acpiphp_context *context);
static void free_bridge(struct kref *kref);

/**
 * acpiphp_init_context - Create hotplug context and grab a reference to it.
 * @adev: ACPI device object to create the context for.
 *
 * Call under acpi_hp_context_lock.
 */
static struct acpiphp_context *acpiphp_init_context(struct acpi_device *adev)
{
	struct acpiphp_context *context;

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

	context->refcount = 1;
	context->hp.notify = acpiphp_hotplug_notify;
	context->hp.fixup = acpiphp_post_dock_fixup;
	acpi_set_hp_context(adev, &context->hp);
	return context;
}

/**
 * acpiphp_get_context - Get hotplug context and grab a reference to it.
 * @adev: ACPI device object to get the context for.
 *
 * Call under acpi_hp_context_lock.
 */
static struct acpiphp_context *acpiphp_get_context(struct acpi_device *adev)
{
	struct acpiphp_context *context;

	if (!adev->hp)
		return NULL;

	context = to_acpiphp_context(adev->hp);
	context->refcount++;
	return context;
}

/**
 * acpiphp_put_context - Drop a reference to ACPI hotplug context.
 * @context: ACPI hotplug context to drop a reference to.
 *
 * The context object is removed if there are no more references to it.
 *
 * Call under acpi_hp_context_lock.
 */
static void acpiphp_put_context(struct acpiphp_context *context)
{
	if (--context->refcount)
		return;

	WARN_ON(context->bridge);
	context->hp.self->hp = NULL;
	kfree(context);
}

static inline void get_bridge(struct acpiphp_bridge *bridge)
{
	kref_get(&bridge->ref);
}

static inline void put_bridge(struct acpiphp_bridge *bridge)
{
	kref_put(&bridge->ref, free_bridge);
}

static struct acpiphp_context *acpiphp_grab_context(struct acpi_device *adev)
{
	struct acpiphp_context *context;

	acpi_lock_hp_context();
	context = acpiphp_get_context(adev);
	if (!context || context->func.parent->is_going_away) {
		acpi_unlock_hp_context();
		return NULL;
	}
	get_bridge(context->func.parent);
	acpiphp_put_context(context);
	acpi_unlock_hp_context();
	return context;
}

static void acpiphp_let_context_go(struct acpiphp_context *context)
{
	put_bridge(context->func.parent);
}

static void free_bridge(struct kref *kref)
{
	struct acpiphp_context *context;
	struct acpiphp_bridge *bridge;
	struct acpiphp_slot *slot, *next;
	struct acpiphp_func *func, *tmp;

	acpi_lock_hp_context();

	bridge = container_of(kref, struct acpiphp_bridge, ref);

	list_for_each_entry_safe(slot, next, &bridge->slots, node) {
		list_for_each_entry_safe(func, tmp, &slot->funcs, sibling)
			acpiphp_put_context(func_to_context(func));

		kfree(slot);
	}

	context = bridge->context;
	/* Root bridges will not have hotplug context. */
	if (context) {
		/* Release the reference taken by acpiphp_enumerate_slots(). */
		put_bridge(context->func.parent);
		context->bridge = NULL;
		acpiphp_put_context(context);
	}

	put_device(&bridge->pci_bus->dev);
	pci_dev_put(bridge->pci_dev);
	kfree(bridge);

	acpi_unlock_hp_context();
}

/**
 * acpiphp_post_dock_fixup - Post-dock fixups for PCI devices.
 * @adev: ACPI device object corresponding to a PCI device.
 *
 * TBD - figure out a way to only call fixups for systems that require them.
 */
static void acpiphp_post_dock_fixup(struct acpi_device *adev)
{
	struct acpiphp_context *context = acpiphp_grab_context(adev);
	struct pci_bus *bus;
	u32 buses;

	if (!context)
		return;

	bus = context->func.slot->bus;
	if (!bus->self)
		goto out;

	/* fixup bad _DCK function that rewrites
	 * secondary bridge on slot
	 */
	pci_read_config_dword(bus->self, PCI_PRIMARY_BUS, &buses);

	if (((buses >> 8) & 0xff) != bus->busn_res.start) {
		buses = (