USB: add USB-Persist facility
This patch (as886) adds the controversial USB-persist facility,
allowing USB devices to persist across a power loss during system
suspend.
The facility is controlled by a new Kconfig option (with appropriate
warnings about the potential dangers); when the option is off the
behavior will remain the same as it is now. But when the option is
on, people will be able to use suspend-to-disk and keep their USB
filesystems intact -- something particularly valuable for small
machines where the root filesystem is on a USB device!
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 77a6627..51d2d30 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -553,45 +553,121 @@
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);
+
+ /* 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_device *hdev = hub->hdev;
+ int port1;
+
+ for (port1 = 1; port1 <= hdev->maxchild; ++port1) {
+ 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);
- 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);
- }
- }
+ /* 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);
}
@@ -1054,32 +1130,63 @@
#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);
@@ -1513,29 +1620,6 @@
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
@@ -3018,7 +3102,7 @@
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);