linux/drivers/pci/hotplug/cpci_hotplug_core.c
Lukas Wunner 51bbf9bee3 PCI: hotplug: Demidlayer registration with the core
When a hotplug driver calls pci_hp_register(), all steps necessary for
registration are carried out in one go, including creation of a kobject
and addition to sysfs.  That's a problem for pciehp once it's converted
to enable/disable the slot exclusively from the IRQ thread:  The thread
needs to be spawned after creation of the kobject (because it uses the
kobject's name), but before addition to sysfs (because it will handle
enable/disable requests submitted via sysfs).

pci_hp_deregister() does offer a ->release callback that's invoked
after deletion from sysfs and before destruction of the kobject.  But
because pci_hp_register() doesn't offer a counterpart, hotplug drivers'
->probe and ->remove code becomes asymmetric, which is error prone
as recently discovered use-after-free bugs in pciehp's ->remove hook
have shown.

In a sense, this appears to be a case of the midlayer antipattern:

   "The core thesis of the "midlayer mistake" is that midlayers are
    bad and should not exist.  That common functionality which it is
    so tempting to put in a midlayer should instead be provided as
    library routines which can [be] used, augmented, or ignored by
    each bottom level driver independently.  Thus every subsystem
    that supports multiple implementations (or drivers) should
    provide a very thin top layer which calls directly into the
    bottom layer drivers, and a rich library of support code that
    eases the implementation of those drivers.  This library is
    available to, but not forced upon, those drivers."
        --  Neil Brown (2009), https://lwn.net/Articles/336262/

The presence of midlayer traits in the PCI hotplug core might be ascribed
to its age:  When it was introduced in February 2002, the blessings of a
library approach might not have been well known:
https://git.kernel.org/tglx/history/c/a8a2069f432c

For comparison, the driver core does offer split functions for creating
a kobject (device_initialize()) and addition to sysfs (device_add()) as
an alternative to carrying out everything at once (device_register()).
This was introduced in October 2002:
https://git.kernel.org/tglx/history/c/8b290eb19962

The odd ->release callback in the PCI hotplug core was added in 2003:
https://git.kernel.org/tglx/history/c/69f8d663b595

Clearly, a library approach would not force every hotplug driver to
implement a ->release callback, but rather allow the driver to remove
the sysfs files, release its data structures and finally destroy the
kobject.  Alternatively, a driver may choose to remove everything with
pci_hp_deregister(), then release its data structures.

To this end, offer drivers pci_hp_initialize() and pci_hp_add() as a
split-up version of pci_hp_register().  Likewise, offer pci_hp_del()
and pci_hp_destroy() as a split-up version of pci_hp_deregister().

Eliminate the ->release callback and move its code into each driver's
teardown routine.

Declare pci_hp_deregister() void, in keeping with the usual kernel
pattern that enablement can fail, but disablement cannot.  It only
returned an error if the caller passed in a NULL pointer or a slot which
has never or is no longer registered or is sharing its name with another
slot.  Those would be bugs, so WARN about them.  Few hotplug drivers
actually checked the return value and those that did only printed a
useless error message to dmesg.  Remove that.

For most drivers the conversion was straightforward since it doesn't
matter whether the code in the ->release callback is executed before or
after destruction of the kobject.  But in the case of ibmphp, it was
unclear to me whether setting slot_cur->ctrl and slot_cur->bus_on to
NULL needs to happen before the kobject is destroyed, so I erred on
the side of caution and ensured that the order stays the same.  Another
nontrivial case is pnv_php, I've found the list and kref logic difficult
to understand, however my impression was that it is safe to delete the
list element and drop the references until after the kobject is
destroyed.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>  # drivers/platform/x86
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Scott Murray <scott@spiteful.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Gavin Shan <gwshan@linux.vnet.ibm.com>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Corentin Chary <corentin.chary@gmail.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Andy Shevchenko <andy@infradead.org>
2018-07-23 17:04:13 -05:00

703 lines
16 KiB
C

// SPDX-License-Identifier: GPL-2.0+
/*
* CompactPCI Hot Plug Driver
*
* Copyright (C) 2002,2005 SOMA Networks, Inc.
* Copyright (C) 2001 Greg Kroah-Hartman (greg@kroah.com)
* Copyright (C) 2001 IBM Corp.
*
* All rights reserved.
*
* Send feedback to <scottm@somanetworks.com>
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/pci_hotplug.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/atomic.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include "cpci_hotplug.h"
#define DRIVER_AUTHOR "Scott Murray <scottm@somanetworks.com>"
#define DRIVER_DESC "CompactPCI Hot Plug Core"
#define MY_NAME "cpci_hotplug"
#define dbg(format, arg...) \
do { \
if (cpci_debug) \
printk(KERN_DEBUG "%s: " format "\n", \
MY_NAME, ## arg); \
} while (0)
#define err(format, arg...) printk(KERN_ERR "%s: " format "\n", MY_NAME, ## arg)
#define info(format, arg...) printk(KERN_INFO "%s: " format "\n", MY_NAME, ## arg)
#define warn(format, arg...) printk(KERN_WARNING "%s: " format "\n", MY_NAME, ## arg)
/* local variables */
static DECLARE_RWSEM(list_rwsem);
static LIST_HEAD(slot_list);
static int slots;
static atomic_t extracting;
int cpci_debug;
static struct cpci_hp_controller *controller;
static struct task_struct *cpci_thread;
static int thread_finished;
static int enable_slot(struct hotplug_slot *slot);
static int disable_slot(struct hotplug_slot *slot);
static int set_attention_status(struct hotplug_slot *slot, u8 value);
static int get_power_status(struct hotplug_slot *slot, u8 *value);
static int get_attention_status(struct hotplug_slot *slot, u8 *value);
static int get_adapter_status(struct hotplug_slot *slot, u8 *value);
static int get_latch_status(struct hotplug_slot *slot, u8 *value);
static struct hotplug_slot_ops cpci_hotplug_slot_ops = {
.enable_slot = enable_slot,
.disable_slot = disable_slot,
.set_attention_status = set_attention_status,
.get_power_status = get_power_status,
.get_attention_status = get_attention_status,
.get_adapter_status = get_adapter_status,
.get_latch_status = get_latch_status,
};
static int
update_latch_status(struct hotplug_slot *hotplug_slot, u8 value)
{
struct hotplug_slot_info info;
memcpy(&info, hotplug_slot->info, sizeof(struct hotplug_slot_info));
info.latch_status = value;
return pci_hp_change_slot_info(hotplug_slot, &info);
}
static int
update_adapter_status(struct hotplug_slot *hotplug_slot, u8 value)
{
struct hotplug_slot_info info;
memcpy(&info, hotplug_slot->info, sizeof(struct hotplug_slot_info));
info.adapter_status = value;
return pci_hp_change_slot_info(hotplug_slot, &info);
}
static int
enable_slot(struct hotplug_slot *hotplug_slot)
{
struct slot *slot = hotplug_slot->private;
int retval = 0;
dbg("%s - physical_slot = %s", __func__, slot_name(slot));
if (controller->ops->set_power)
retval = controller->ops->set_power(slot, 1);
return retval;
}
static int
disable_slot(struct hotplug_slot *hotplug_slot)
{
struct slot *slot = hotplug_slot->private;
int retval = 0;
dbg("%s - physical_slot = %s", __func__, slot_name(slot));
down_write(&list_rwsem);
/* Unconfigure device */
dbg("%s - unconfiguring slot %s", __func__, slot_name(slot));
retval = cpci_unconfigure_slot(slot);
if (retval) {
err("%s - could not unconfigure slot %s",
__func__, slot_name(slot));
goto disable_error;
}
dbg("%s - finished unconfiguring slot %s", __func__, slot_name(slot));
/* Clear EXT (by setting it) */
if (cpci_clear_ext(slot)) {
err("%s - could not clear EXT for slot %s",
__func__, slot_name(slot));
retval = -ENODEV;
goto disable_error;
}
cpci_led_on(slot);
if (controller->ops->set_power) {
retval = controller->ops->set_power(slot, 0);
if (retval)
goto disable_error;
}
if (update_adapter_status(slot->hotplug_slot, 0))
warn("failure to update adapter file");
if (slot->extracting) {
slot->extracting = 0;
atomic_dec(&extracting);
}
disable_error:
up_write(&list_rwsem);
return retval;
}
static u8
cpci_get_power_status(struct slot *slot)
{
u8 power = 1;
if (controller->ops->get_power)
power = controller->ops->get_power(slot);
return power;
}
static int
get_power_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = hotplug_slot->private;
*value = cpci_get_power_status(slot);
return 0;
}
static int
get_attention_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = hotplug_slot->private;
*value = cpci_get_attention_status(slot);
return 0;
}
static int
set_attention_status(struct hotplug_slot *hotplug_slot, u8 status)
{
return cpci_set_attention_status(hotplug_slot->private, status);
}
static int
get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
*value = hotplug_slot->info->adapter_status;
return 0;
}
static int
get_latch_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
*value = hotplug_slot->info->latch_status;
return 0;
}
static void release_slot(struct slot *slot)
{
kfree(slot->hotplug_slot->info);
kfree(slot->hotplug_slot);
pci_dev_put(slot->dev);
kfree(slot);
}
#define SLOT_NAME_SIZE 6
int
cpci_hp_register_bus(struct pci_bus *bus, u8 first, u8 last)
{
struct slot *slot;
struct hotplug_slot *hotplug_slot;
struct hotplug_slot_info *info;
char name[SLOT_NAME_SIZE];
int status;
int i;
if (!(controller && bus))
return -ENODEV;
/*
* Create a structure for each slot, and register that slot
* with the pci_hotplug subsystem.
*/
for (i = first; i <= last; ++i) {
slot = kzalloc(sizeof(struct slot), GFP_KERNEL);
if (!slot) {
status = -ENOMEM;
goto error;
}
hotplug_slot =
kzalloc(sizeof(struct hotplug_slot), GFP_KERNEL);
if (!hotplug_slot) {
status = -ENOMEM;
goto error_slot;
}
slot->hotplug_slot = hotplug_slot;
info = kzalloc(sizeof(struct hotplug_slot_info), GFP_KERNEL);
if (!info) {
status = -ENOMEM;
goto error_hpslot;
}
hotplug_slot->info = info;
slot->bus = bus;
slot->number = i;
slot->devfn = PCI_DEVFN(i, 0);
snprintf(name, SLOT_NAME_SIZE, "%02x:%02x", bus->number, i);
hotplug_slot->private = slot;
hotplug_slot->ops = &cpci_hotplug_slot_ops;
/*
* Initialize the slot info structure with some known
* good values.
*/
dbg("initializing slot %s", name);
info->power_status = cpci_get_power_status(slot);
info->attention_status = cpci_get_attention_status(slot);
dbg("registering slot %s", name);
status = pci_hp_register(slot->hotplug_slot, bus, i, name);
if (status) {
err("pci_hp_register failed with error %d", status);
goto error_info;
}
dbg("slot registered with name: %s", slot_name(slot));
/* Add slot to our internal list */
down_write(&list_rwsem);
list_add(&slot->slot_list, &slot_list);
slots++;
up_write(&list_rwsem);
}
return 0;
error_info:
kfree(info);
error_hpslot:
kfree(hotplug_slot);
error_slot:
kfree(slot);
error:
return status;
}
EXPORT_SYMBOL_GPL(cpci_hp_register_bus);
int
cpci_hp_unregister_bus(struct pci_bus *bus)
{
struct slot *slot;
struct slot *tmp;
int status = 0;
down_write(&list_rwsem);
if (!slots) {
up_write(&list_rwsem);
return -1;
}
list_for_each_entry_safe(slot, tmp, &slot_list, slot_list) {
if (slot->bus == bus) {
list_del(&slot->slot_list);
slots--;
dbg("deregistering slot %s", slot_name(slot));
pci_hp_deregister(slot->hotplug_slot);
release_slot(slot);
}
}
up_write(&list_rwsem);
return status;
}
EXPORT_SYMBOL_GPL(cpci_hp_unregister_bus);
/* This is the interrupt mode interrupt handler */
static irqreturn_t
cpci_hp_intr(int irq, void *data)
{
dbg("entered cpci_hp_intr");
/* Check to see if it was our interrupt */
if ((controller->irq_flags & IRQF_SHARED) &&
!controller->ops->check_irq(controller->dev_id)) {
dbg("exited cpci_hp_intr, not our interrupt");
return IRQ_NONE;
}
/* Disable ENUM interrupt */
controller->ops->disable_irq();
/* Trigger processing by the event thread */
wake_up_process(cpci_thread);
return IRQ_HANDLED;
}
/*
* According to PICMG 2.1 R2.0, section 6.3.2, upon
* initialization, the system driver shall clear the
* INS bits of the cold-inserted devices.
*/
static int
init_slots(int clear_ins)
{
struct slot *slot;
struct pci_dev *dev;
dbg("%s - enter", __func__);
down_read(&list_rwsem);
if (!slots) {
up_read(&list_rwsem);
return -1;
}
list_for_each_entry(slot, &slot_list, slot_list) {
dbg("%s - looking at slot %s", __func__, slot_name(slot));
if (clear_ins && cpci_check_and_clear_ins(slot))
dbg("%s - cleared INS for slot %s",
__func__, slot_name(slot));
dev = pci_get_slot(slot->bus, PCI_DEVFN(slot->number, 0));
if (dev) {
if (update_adapter_status(slot->hotplug_slot, 1))
warn("failure to update adapter file");
if (update_latch_status(slot->hotplug_slot, 1))
warn("failure to update latch file");
slot->dev = dev;
}
}
up_read(&list_rwsem);
dbg("%s - exit", __func__);
return 0;
}
static int
check_slots(void)
{
struct slot *slot;
int extracted;
int inserted;
u16 hs_csr;
down_read(&list_rwsem);
if (!slots) {
up_read(&list_rwsem);
err("no slots registered, shutting down");
return -1;
}
extracted = inserted = 0;
list_for_each_entry(slot, &slot_list, slot_list) {
dbg("%s - looking at slot %s", __func__, slot_name(slot));
if (cpci_check_and_clear_ins(slot)) {
/*
* Some broken hardware (e.g. PLX 9054AB) asserts
* ENUM# twice...
*/
if (slot->dev) {
warn("slot %s already inserted",
slot_name(slot));
inserted++;
continue;
}
/* Process insertion */
dbg("%s - slot %s inserted", __func__, slot_name(slot));
/* GSM, debug */
hs_csr = cpci_get_hs_csr(slot);
dbg("%s - slot %s HS_CSR (1) = %04x",
__func__, slot_name(slot), hs_csr);
/* Configure device */
dbg("%s - configuring slot %s",
__func__, slot_name(slot));
if (cpci_configure_slot(slot)) {
err("%s - could not configure slot %s",
__func__, slot_name(slot));
continue;
}
dbg("%s - finished configuring slot %s",
__func__, slot_name(slot));
/* GSM, debug */
hs_csr = cpci_get_hs_csr(slot);
dbg("%s - slot %s HS_CSR (2) = %04x",
__func__, slot_name(slot), hs_csr);
if (update_latch_status(slot->hotplug_slot, 1))
warn("failure to update latch file");
if (update_adapter_status(slot->hotplug_slot, 1))
warn("failure to update adapter file");
cpci_led_off(slot);
/* GSM, debug */
hs_csr = cpci_get_hs_csr(slot);
dbg("%s - slot %s HS_CSR (3) = %04x",
__func__, slot_name(slot), hs_csr);
inserted++;
} else if (cpci_check_ext(slot)) {
/* Process extraction request */
dbg("%s - slot %s extracted",
__func__, slot_name(slot));
/* GSM, debug */
hs_csr = cpci_get_hs_csr(slot);
dbg("%s - slot %s HS_CSR = %04x",
__func__, slot_name(slot), hs_csr);
if (!slot->extracting) {
if (update_latch_status(slot->hotplug_slot, 0))
warn("failure to update latch file");
slot->extracting = 1;
atomic_inc(&extracting);
}
extracted++;
} else if (slot->extracting) {
hs_csr = cpci_get_hs_csr(slot);
if (hs_csr == 0xffff) {
/*
* Hmmm, we're likely hosed at this point, should we
* bother trying to tell the driver or not?
*/
err("card in slot %s was improperly removed",
slot_name(slot));
if (update_adapter_status(slot->hotplug_slot, 0))
warn("failure to update adapter file");
slot->extracting = 0;
atomic_dec(&extracting);
}
}
}
up_read(&list_rwsem);
dbg("inserted=%d, extracted=%d, extracting=%d",
inserted, extracted, atomic_read(&extracting));
if (inserted || extracted)
return extracted;
else if (!atomic_read(&extracting)) {
err("cannot find ENUM# source, shutting down");
return -1;
}
return 0;
}
/* This is the interrupt mode worker thread body */
static int
event_thread(void *data)
{
int rc;
dbg("%s - event thread started", __func__);
while (1) {
dbg("event thread sleeping");
set_current_state(TASK_INTERRUPTIBLE);
schedule();
if (kthread_should_stop())
break;
do {
rc = check_slots();
if (rc > 0) {
/* Give userspace a chance to handle extraction */
msleep(500);
} else if (rc < 0) {
dbg("%s - error checking slots", __func__);
thread_finished = 1;
goto out;
}
} while (atomic_read(&extracting) && !kthread_should_stop());
if (kthread_should_stop())
break;
/* Re-enable ENUM# interrupt */
dbg("%s - re-enabling irq", __func__);
controller->ops->enable_irq();
}
out:
return 0;
}
/* This is the polling mode worker thread body */
static int
poll_thread(void *data)
{
int rc;
while (1) {
if (kthread_should_stop() || signal_pending(current))
break;
if (controller->ops->query_enum()) {
do {
rc = check_slots();
if (rc > 0) {
/* Give userspace a chance to handle extraction */
msleep(500);
} else if (rc < 0) {
dbg("%s - error checking slots", __func__);
thread_finished = 1;
goto out;
}
} while (atomic_read(&extracting) && !kthread_should_stop());
}
msleep(100);
}
out:
return 0;
}
static int
cpci_start_thread(void)
{
if (controller->irq)
cpci_thread = kthread_run(event_thread, NULL, "cpci_hp_eventd");
else
cpci_thread = kthread_run(poll_thread, NULL, "cpci_hp_polld");
if (IS_ERR(cpci_thread)) {
err("Can't start up our thread");
return PTR_ERR(cpci_thread);
}
thread_finished = 0;
return 0;
}
static void
cpci_stop_thread(void)
{
kthread_stop(cpci_thread);
thread_finished = 1;
}
int
cpci_hp_register_controller(struct cpci_hp_controller *new_controller)
{
int status = 0;
if (controller)
return -1;
if (!(new_controller && new_controller->ops))
return -EINVAL;
if (new_controller->irq) {
if (!(new_controller->ops->enable_irq &&
new_controller->ops->disable_irq))
status = -EINVAL;
if (request_irq(new_controller->irq,
cpci_hp_intr,
new_controller->irq_flags,
MY_NAME,
new_controller->dev_id)) {
err("Can't get irq %d for the hotplug cPCI controller",
new_controller->irq);
status = -ENODEV;
}
dbg("%s - acquired controller irq %d",
__func__, new_controller->irq);
}
if (!status)
controller = new_controller;
return status;
}
EXPORT_SYMBOL_GPL(cpci_hp_register_controller);
static void
cleanup_slots(void)
{
struct slot *slot;
struct slot *tmp;
/*
* Unregister all of our slots with the pci_hotplug subsystem,
* and free up all memory that we had allocated.
*/
down_write(&list_rwsem);
if (!slots)
goto cleanup_null;
list_for_each_entry_safe(slot, tmp, &slot_list, slot_list) {
list_del(&slot->slot_list);
pci_hp_deregister(slot->hotplug_slot);
release_slot(slot);
}
cleanup_null:
up_write(&list_rwsem);
return;
}
int
cpci_hp_unregister_controller(struct cpci_hp_controller *old_controller)
{
int status = 0;
if (controller) {
if (!thread_finished)
cpci_stop_thread();
if (controller->irq)
free_irq(controller->irq, controller->dev_id);
controller = NULL;
cleanup_slots();
} else
status = -ENODEV;
return status;
}
EXPORT_SYMBOL_GPL(cpci_hp_unregister_controller);
int
cpci_hp_start(void)
{
static int first = 1;
int status;
dbg("%s - enter", __func__);
if (!controller)
return -ENODEV;
down_read(&list_rwsem);
if (list_empty(&slot_list)) {
up_read(&list_rwsem);
return -ENODEV;
}
up_read(&list_rwsem);
status = init_slots(first);
if (first)
first = 0;
if (status)
return status;
status = cpci_start_thread();
if (status)
return status;
dbg("%s - thread started", __func__);
if (controller->irq) {
/* Start enum interrupt processing */
dbg("%s - enabling irq", __func__);
controller->ops->enable_irq();
}
dbg("%s - exit", __func__);
return 0;
}
EXPORT_SYMBOL_GPL(cpci_hp_start);
int
cpci_hp_stop(void)
{
if (!controller)
return -ENODEV;
if (controller->irq) {
/* Stop enum interrupt processing */
dbg("%s - disabling irq", __func__);
controller->ops->disable_irq();
}
cpci_stop_thread();
return 0;
}
EXPORT_SYMBOL_GPL(cpci_hp_stop);
int __init
cpci_hotplug_init(int debug)
{
cpci_debug = debug;
return 0;
}