Firewire, CompactFlash, MMC, external SATA, or even IDE hotplug bays)
before suspending; then remount them after resuming.
+There is a work-around for this problem. For more information, see
+Documentation/usb/persist.txt.
+
Q: I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were
compiled with the similar configuration files. Anyway I found that
suspend to disk (and resume) is much slower on 2.6.16 compared to
--- /dev/null
+ USB device persistence during system suspend
+
+ Alan Stern <stern@rowland.harvard.edu>
+
+ September 2, 2006 (Updated March 27, 2007)
+
+
+ What is the problem?
+
+According to the USB specification, when a USB bus is suspended the
+bus must continue to supply suspend current (around 1-5 mA). This
+is so that devices can maintain their internal state and hubs can
+detect connect-change events (devices being plugged in or unplugged).
+The technical term is "power session".
+
+If a USB device's power session is interrupted then the system is
+required to behave as though the device has been unplugged. It's a
+conservative approach; in the absence of suspend current the computer
+has no way to know what has actually happened. Perhaps the same
+device is still attached or perhaps it was removed and a different
+device plugged into the port. The system must assume the worst.
+
+By default, Linux behaves according to the spec. If a USB host
+controller loses power during a system suspend, then when the system
+wakes up all the devices attached to that controller are treated as
+though they had disconnected. This is always safe and it is the
+"officially correct" thing to do.
+
+For many sorts of devices this behavior doesn't matter in the least.
+If the kernel wants to believe that your USB keyboard was unplugged
+while the system was asleep and a new keyboard was plugged in when the
+system woke up, who cares? It'll still work the same when you type on
+it.
+
+Unfortunately problems _can_ arise, particularly with mass-storage
+devices. The effect is exactly the same as if the device really had
+been unplugged while the system was suspended. If you had a mounted
+filesystem on the device, you're out of luck -- everything in that
+filesystem is now inaccessible. This is especially annoying if your
+root filesystem was located on the device, since your system will
+instantly crash.
+
+Loss of power isn't the only mechanism to worry about. Anything that
+interrupts a power session will have the same effect. For example,
+even though suspend current may have been maintained while the system
+was asleep, on many systems during the initial stages of wakeup the
+firmware (i.e., the BIOS) resets the motherboard's USB host
+controllers. Result: all the power sessions are destroyed and again
+it's as though you had unplugged all the USB devices. Yes, it's
+entirely the BIOS's fault, but that doesn't do _you_ any good unless
+you can convince the BIOS supplier to fix the problem (lots of luck!).
+
+On many systems the USB host controllers will get reset after a
+suspend-to-RAM. On almost all systems, no suspend current is
+available during suspend-to-disk (also known as swsusp). You can
+check the kernel log after resuming to see if either of these has
+happened; look for lines saying "root hub lost power or was reset".
+
+In practice, people are forced to unmount any filesystems on a USB
+device before suspending. If the root filesystem is on a USB device,
+the system can't be suspended at all. (All right, it _can_ be
+suspended -- but it will crash as soon as it wakes up, which isn't
+much better.)
+
+
+ What is the solution?
+
+Setting CONFIG_USB_PERSIST will cause the kernel to work around these
+issues. It enables a mode in which the core USB device data
+structures are allowed to persist across a power-session disruption.
+It works like this. If the kernel sees that a USB host controller is
+not in the expected state during resume (i.e., if the controller was
+reset or otherwise had lost power) then it applies a persistence check
+to each of the USB devices below that controller. It doesn't try to
+resume the device; that can't work once the power session is gone.
+Instead it issues a USB port reset and then re-enumerates the device.
+(This is exactly the same thing that happens whenever a USB device is
+reset.) If the re-enumeration shows that the device now attached to
+that port has the same descriptors as before, including the Vendor and
+Product IDs, then the kernel continues to use the same device
+structure. In effect, the kernel treats the device as though it had
+merely been reset instead of unplugged.
+
+If no device is now attached to the port, or if the descriptors are
+different from what the kernel remembers, then the treatment is what
+you would expect. The kernel destroys the old device structure and
+behaves as though the old device had been unplugged and a new device
+plugged in, just as it would without the CONFIG_USB_PERSIST option.
+
+The end result is that the USB device remains available and usable.
+Filesystem mounts and memory mappings are unaffected, and the world is
+now a good and happy place.
+
+
+ Is this the best solution?
+
+Perhaps not. Arguably, keeping track of mounted filesystems and
+memory mappings across device disconnects should be handled by a
+centralized Logical Volume Manager. Such a solution would allow you
+to plug in a USB flash device, create a persistent volume associated
+with it, unplug the flash device, plug it back in later, and still
+have the same persistent volume associated with the device. As such
+it would be more far-reaching than CONFIG_USB_PERSIST.
+
+On the other hand, writing a persistent volume manager would be a big
+job and using it would require significant input from the user. This
+solution is much quicker and easier -- and it exists now, a giant
+point in its favor!
+
+Furthermore, the USB_PERSIST option applies to _all_ USB devices, not
+just mass-storage devices. It might turn out to be equally useful for
+other device types, such as network interfaces.
+
+
+ WARNING: Using CONFIG_USB_PERSIST can be dangerous!!
+
+When recovering an interrupted power session the kernel does its best
+to make sure the USB device hasn't been changed; that is, the same
+device is still plugged into the port as before. But the checks
+aren't guaranteed to be 100% accurate.
+
+If you replace one USB device with another of the same type (same
+manufacturer, same IDs, and so on) there's an excellent chance the
+kernel won't detect the change. Serial numbers and other strings are
+not compared. In many cases it wouldn't help if they were, because
+manufacturers frequently omit serial numbers entirely in their
+devices.
+
+Furthermore it's quite possible to leave a USB device exactly the same
+while changing its media. If you replace the flash memory card in a
+USB card reader while the system is asleep, the kernel will have no
+way to know you did it. The kernel will assume that nothing has
+happened and will continue to use the partition tables, inodes, and
+memory mappings for the old card.
+
+If the kernel gets fooled in this way, it's almost certain to cause
+data corruption and to crash your system. You'll have no one to blame
+but yourself.
+
+YOU HAVE BEEN WARNED! USE AT YOUR OWN RISK!
+
+That having been said, most of the time there shouldn't be any trouble
+at all. The "persist" feature can be extremely useful. Make the most
+of it.
hid_suspend(intf, PMSG_ON);
}
-static void hid_post_reset(struct usb_interface *intf)
+static void hid_post_reset(struct usb_interface *intf, int reset_resume)
{
struct usb_device *dev = interface_to_usbdev (intf);
If you are unsure about this, say N here.
+config USB_PERSIST
+ bool "USB device persistence during system suspend (DANGEROUS)"
+ depends on USB && PM && EXPERIMENTAL
+ default n
+ help
+ If you say Y here, USB device data structures will remain
+ persistent across system suspend, even if the USB bus loses
+ power. (This includes software-suspend, also known as swsusp,
+ or suspend-to-disk.) The devices will reappear as if by magic
+ when the system wakes up, with no need to unmount USB filesystems,
+ rmmod host-controller drivers, or do anything else.
+
+ WARNING: This option can be dangerous!
+
+ If a USB device is replaced by another of the same type while
+ the system is asleep, there's a good chance the kernel won't
+ detect the change. Likewise if the media in a USB storage
+ device is replaced. When this happens it's almost certain to
+ cause data corruption and maybe even crash your system.
+
+ If you are unsure, say N here.
+
config USB_OTG
bool
depends on USB && EXPERIMENTAL
struct usb_device_driver *udriver;
int status = 0;
- if (udev->state == USB_STATE_NOTATTACHED ||
- udev->state != USB_STATE_SUSPENDED)
+ if (udev->state == USB_STATE_NOTATTACHED)
+ goto done;
+ if (udev->state != USB_STATE_SUSPENDED && !udev->reset_resume)
goto done;
/* Can't resume it if it doesn't have a driver. */
}
/* Caller has locked intf's usb_device's pm_mutex */
-static int usb_resume_interface(struct usb_interface *intf)
+static int usb_resume_interface(struct usb_interface *intf, int reset_resume)
{
struct usb_driver *driver;
int status = 0;
}
driver = to_usb_driver(intf->dev.driver);
- if (driver->resume) {
+ if (reset_resume && driver->post_reset)
+ driver->post_reset(intf, reset_resume);
+ else if (driver->resume) {
status = driver->resume(intf);
if (status)
dev_err(&intf->dev, "%s error %d\n",
"resume", status);
- else
- mark_active(intf);
- } else {
+ } else
dev_warn(&intf->dev, "no resume for driver %s?\n",
driver->name);
- mark_active(intf);
- }
done:
// dev_dbg(&intf->dev, "%s: status %d\n", __FUNCTION__, status);
+ if (status == 0)
+ mark_active(intf);
return status;
}
if (status != 0) {
while (--i >= 0) {
intf = udev->actconfig->interface[i];
- usb_resume_interface(intf);
+ usb_resume_interface(intf, 0);
}
/* Try another autosuspend when the interfaces aren't busy */
}
} else {
- /* Needed only for setting udev->dev.power.power_state.event
- * and for possible debugging message. */
+ /* Needed for setting udev->dev.power.power_state.event,
+ * for possible debugging message, and for reset_resume. */
status = usb_resume_device(udev);
}
if (status == 0 && udev->actconfig) {
for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
intf = udev->actconfig->interface[i];
- usb_resume_interface(intf);
+ usb_resume_interface(intf, udev->reset_resume);
}
}
done:
// dev_dbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
+ udev->reset_resume = 0;
return status;
}
if (!is_usb_device(dev)) /* Ignore PM for interfaces */
return 0;
udev = to_usb_device(dev);
- if (udev->autoresume_disabled)
- return -EPERM;
+
+ /* If autoresume is disabled then we also want to prevent resume
+ * during system wakeup. However, a "persistent-device" reset-resume
+ * after power loss counts as a wakeup event. So allow a
+ * reset-resume to occur if remote wakeup is enabled. */
+ if (udev->autoresume_disabled) {
+ if (!(udev->reset_resume && udev->do_remote_wakeup))
+ return -EPERM;
+ }
return usb_external_resume_device(udev);
}
{
int rc;
- rc = usb_port_resume(udev);
+ if (udev->reset_resume)
+ rc = usb_reset_suspended_device(udev);
+ else
+ rc = usb_port_resume(udev);
/* Root hubs don't have upstream ports to resume or reset,
* so the line above won't do much for them. We have to
static int hub_port_disable(struct usb_hub *hub, int port1, int set_state)
{
struct usb_device *hdev = hub->hdev;
- int ret;
+ int ret = 0;
- if (hdev->children[port1-1] && set_state) {
+ if (hdev->children[port1-1] && set_state)
usb_set_device_state(hdev->children[port1-1],
USB_STATE_NOTATTACHED);
- }
- ret = clear_port_feature(hdev, port1, USB_PORT_FEAT_ENABLE);
+ if (!hub->error)
+ ret = clear_port_feature(hdev, port1, USB_PORT_FEAT_ENABLE);
if (ret)
dev_err(hub->intfdev, "cannot disable port %d (err = %d)\n",
- port1, ret);
-
+ port1, ret);
return ret;
}
+/*
+ * Disable a port and mark a logical connnect-change event, so that some
+ * time later khubd will disconnect() any existing usb_device on the port
+ * and will re-enumerate if there actually is a device attached.
+ */
+static void hub_port_logical_disconnect(struct usb_hub *hub, int port1)
+{
+ dev_dbg(hub->intfdev, "logical disconnect on port %d\n", port1);
+ hub_port_disable(hub, port1, 1);
-/* caller has locked the hub device */
-static void hub_pre_reset(struct usb_interface *intf)
+ /* FIXME let caller ask to power down the port:
+ * - some devices won't enumerate without a VBUS power cycle
+ * - SRP saves power that way
+ * - ... new call, TBD ...
+ * That's easy if this hub can switch power per-port, and
+ * khubd reactivates the port later (timer, SRP, etc).
+ * Powerdown must be optional, because of reset/DFU.
+ */
+
+ set_bit(port1, hub->change_bits);
+ kick_khubd(hub);
+}
+
+static void disconnect_all_children(struct usb_hub *hub, int logical)
{
- struct usb_hub *hub = usb_get_intfdata(intf);
struct usb_device *hdev = hub->hdev;
int port1;
for (port1 = 1; port1 <= hdev->maxchild; ++port1) {
- if (hdev->children[port1 - 1]) {
- usb_disconnect(&hdev->children[port1 - 1]);
- if (hub->error == 0)
- hub_port_disable(hub, port1, 0);
+ if (hdev->children[port1-1]) {
+ if (logical)
+ hub_port_logical_disconnect(hub, port1);
+ else
+ usb_disconnect(&hdev->children[port1-1]);
+ }
+ }
+}
+
+#ifdef CONFIG_USB_PERSIST
+
+#define USB_PERSIST 1
+
+/* For "persistent-device" resets we must mark the child devices for reset
+ * and turn off a possible connect-change status (so khubd won't disconnect
+ * them later).
+ */
+static void mark_children_for_reset_resume(struct usb_hub *hub)
+{
+ struct usb_device *hdev = hub->hdev;
+ int port1;
+
+ for (port1 = 1; port1 <= hdev->maxchild; ++port1) {
+ struct usb_device *child = hdev->children[port1-1];
+
+ if (child) {
+ child->reset_resume = 1;
+ clear_port_feature(hdev, port1,
+ USB_PORT_FEAT_C_CONNECTION);
}
}
+}
+
+#else
+
+#define USB_PERSIST 0
+
+static inline void mark_children_for_reset_resume(struct usb_hub *hub)
+{ }
+
+#endif /* CONFIG_USB_PERSIST */
+
+/* caller has locked the hub device */
+static void hub_pre_reset(struct usb_interface *intf)
+{
+ struct usb_hub *hub = usb_get_intfdata(intf);
+
+ /* This routine doesn't run as part of a reset-resume, so it's safe
+ * to disconnect all the drivers below the hub.
+ */
+ disconnect_all_children(hub, 0);
hub_quiesce(hub);
}
/* caller has locked the hub device */
-static void hub_post_reset(struct usb_interface *intf)
+static void hub_post_reset(struct usb_interface *intf, int reset_resume)
{
struct usb_hub *hub = usb_get_intfdata(intf);
- hub_activate(hub);
hub_power_on(hub);
+ if (reset_resume) {
+ if (USB_PERSIST)
+ mark_children_for_reset_resume(hub);
+ else {
+ /* Reset-resume doesn't call pre_reset, so we have to
+ * disconnect the children here. But we may not lock
+ * the child devices, so we have to do a "logical"
+ * disconnect.
+ */
+ disconnect_all_children(hub, 1);
+ }
+ }
+ hub_activate(hub);
}
#ifdef CONFIG_PM
+/**
+ * usb_reset_suspended_device - reset a suspended device instead of resuming it
+ * @udev: device to be reset instead of resumed
+ *
+ * If a host controller doesn't maintain VBUS suspend current during a
+ * system sleep or is reset when the system wakes up, all the USB
+ * power sessions below it will be broken. This is especially troublesome
+ * for mass-storage devices containing mounted filesystems, since the
+ * device will appear to have disconnected and all the memory mappings
+ * to it will be lost.
+ *
+ * As an alternative, this routine attempts to recover power sessions for
+ * devices that are still present by resetting them instead of resuming
+ * them. If all goes well, the devices will appear to persist across the
+ * the interruption of the power sessions.
+ *
+ * This facility is inherently dangerous. Although usb_reset_device()
+ * makes every effort to insure that the same device is present after the
+ * reset as before, it cannot provide a 100% guarantee. Furthermore it's
+ * quite possible for a device to remain unaltered but its media to be
+ * changed. If the user replaces a flash memory card while the system is
+ * asleep, he will have only himself to blame when the filesystem on the
+ * new card is corrupted and the system crashes.
+ */
+int usb_reset_suspended_device(struct usb_device *udev)
+{
+ int rc = 0;
+
+ dev_dbg(&udev->dev, "usb %sresume\n", "reset-");
+
+ /* After we're done the device won't be suspended any more.
+ * In addition, the reset won't work if udev->state is SUSPENDED.
+ */
+ usb_set_device_state(udev, udev->actconfig
+ ? USB_STATE_CONFIGURED
+ : USB_STATE_ADDRESS);
+
+ /* Root hubs don't need to be (and can't be) reset */
+ if (udev->parent)
+ rc = usb_reset_device(udev);
+ return rc;
+}
+
/**
* usb_root_hub_lost_power - called by HCD if the root hub lost Vbus power
* @rhdev: struct usb_device for the root hub
*
* The USB host controller driver calls this function when its root hub
* is resumed and Vbus power has been interrupted or the controller
- * has been reset. The routine marks all the children of the root hub
- * as NOTATTACHED and marks logical connect-change events on their ports.
+ * has been reset. The routine marks @rhdev as having lost power. When
+ * the hub driver is resumed it will take notice; if CONFIG_USB_PERSIST
+ * is enabled then it will carry out power-session recovery, otherwise
+ * it will disconnect all the child devices.
*/
void usb_root_hub_lost_power(struct usb_device *rhdev)
{
- struct usb_hub *hub;
- int port1;
- unsigned long flags;
-
dev_warn(&rhdev->dev, "root hub lost power or was reset\n");
-
- spin_lock_irqsave(&device_state_lock, flags);
- hub = hdev_to_hub(rhdev);
- for (port1 = 1; port1 <= rhdev->maxchild; ++port1) {
- if (rhdev->children[port1 - 1]) {
- recursively_mark_NOTATTACHED(
- rhdev->children[port1 - 1]);
- set_bit(port1, hub->change_bits);
- }
- }
- spin_unlock_irqrestore(&device_state_lock, flags);
+ rhdev->reset_resume = 1;
}
EXPORT_SYMBOL_GPL(usb_root_hub_lost_power);
return status;
}
-/*
- * Disable a port and mark a logical connnect-change event, so that some
- * time later khubd will disconnect() any existing usb_device on the port
- * and will re-enumerate if there actually is a device attached.
- */
-static void hub_port_logical_disconnect(struct usb_hub *hub, int port1)
-{
- dev_dbg(hub->intfdev, "logical disconnect on port %d\n", port1);
- hub_port_disable(hub, port1, 1);
-
- /* FIXME let caller ask to power down the port:
- * - some devices won't enumerate without a VBUS power cycle
- * - SRP saves power that way
- * - ... new call, TBD ...
- * That's easy if this hub can switch power per-port, and
- * khubd reactivates the port later (timer, SRP, etc).
- * Powerdown must be optional, because of reset/DFU.
- */
-
- set_bit(port1, hub->change_bits);
- kick_khubd(hub);
-}
-
#ifdef CONFIG_PM
#ifdef CONFIG_USB_SUSPEND
cintf->dev.driver) {
drv = to_usb_driver(cintf->dev.driver);
if (drv->post_reset)
- (drv->post_reset)(cintf);
+ (drv->post_reset)(cintf, 0);
}
if (cintf != iface)
up(&cintf->dev.sem);
extern void usb_autosuspend_work(struct work_struct *work);
extern int usb_port_suspend(struct usb_device *dev);
extern int usb_port_resume(struct usb_device *dev);
+extern int usb_reset_suspended_device(struct usb_device *udev);
extern int usb_external_suspend_device(struct usb_device *udev,
pm_message_t msg);
extern int usb_external_resume_device(struct usb_device *udev);
mutex_lock(&us->dev_mutex);
}
-static void storage_post_reset(struct usb_interface *iface)
+static void storage_post_reset(struct usb_interface *iface, int reset_resume)
{
struct us_data *us = usb_get_intfdata(iface);
/* FIXME: Notify the subdrivers that they need to reinitialize
* the device */
- mutex_unlock(&us->dev_mutex);
+
+ /* If this is a reset-resume then the pre_reset routine wasn't
+ * called, so we don't need to unlock the mutex. */
+ if (!reset_resume)
+ mutex_unlock(&us->dev_mutex);
}
/*
unsigned auto_pm:1; /* autosuspend/resume in progress */
unsigned do_remote_wakeup:1; /* remote wakeup should be enabled */
+ unsigned reset_resume:1; /* needs reset instead of resume */
unsigned autosuspend_disabled:1; /* autosuspend and autoresume */
unsigned autoresume_disabled:1; /* disabled by the user */
#endif
* @pre_reset: Called by usb_reset_composite_device() when the device
* is about to be reset.
* @post_reset: Called by usb_reset_composite_device() after the device
- * has been reset.
+ * has been reset, or in lieu of @resume following a reset-resume
+ * (i.e., the device is reset instead of being resumed, as might
+ * happen if power was lost). The second argument tells which is
+ * the reason.
* @id_table: USB drivers use ID table to support hotplugging.
* Export this with MODULE_DEVICE_TABLE(usb,...). This must be set
* or your driver's probe function will never get called.
int (*resume) (struct usb_interface *intf);
void (*pre_reset) (struct usb_interface *intf);
- void (*post_reset) (struct usb_interface *intf);
+ void (*post_reset) (struct usb_interface *intf, int reset_resume);
const struct usb_device_id *id_table;
projects / linux-2.6 / commitdiff