USB: debounce before unregistering
This patch (as1080) makes a significant change to the way khubd
handles port connect-change and enable-change events. Both types of
event are now debounced, and the debouncing is carried out _before_ an
existing usb_device is unregistered, instead of afterward.
This means that drivers will have to deal with longer runs of errors
when a device is unplugged, but they are supposed to be prepared for
that in any case.
The advantage is that when an enable-change occurs (caused for example
by electromagnetic interference), the debouncing period will provide
time for the cause of the problem to die away. A simple port reset
(added in a forthcoming patch) will then allow us to recover from the
fault.
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 d14da21..d741b94 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2673,9 +2673,10 @@
struct usb_device *hdev = hub->hdev;
struct device *hub_dev = hub->intfdev;
struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
- u16 wHubCharacteristics = le16_to_cpu(hub->descriptor->wHubCharacteristics);
+ unsigned wHubCharacteristics =
+ le16_to_cpu(hub->descriptor->wHubCharacteristics);
int status, i;
-
+
dev_dbg (hub_dev,
"port %d, status %04x, change %04x, %s\n",
port1, portstatus, portchange, portspeed (portstatus));
@@ -2684,30 +2685,36 @@
set_port_led(hub, port1, HUB_LED_AUTO);
hub->indicator[port1-1] = INDICATOR_AUTO;
}
-
- /* Disconnect any existing devices under this port */
- if (hdev->children[port1-1])
- usb_disconnect(&hdev->children[port1-1]);
- clear_bit(port1, hub->change_bits);
#ifdef CONFIG_USB_OTG
/* during HNP, don't repeat the debounce */
if (hdev->bus->is_b_host)
- portchange &= ~USB_PORT_STAT_C_CONNECTION;
+ portchange &= ~(USB_PORT_STAT_C_CONNECTION |
+ USB_PORT_STAT_C_ENABLE);
#endif
- if (portchange & USB_PORT_STAT_C_CONNECTION) {
+ /* Try to use the debounce delay for protection against
+ * port-enable changes caused, for example, by EMI.
+ */
+ if (portchange & (USB_PORT_STAT_C_CONNECTION |
+ USB_PORT_STAT_C_ENABLE)) {
status = hub_port_debounce(hub, port1);
if (status < 0) {
if (printk_ratelimit())
dev_err (hub_dev, "connect-debounce failed, "
"port %d disabled\n", port1);
- goto done;
+ portstatus &= ~USB_PORT_STAT_CONNECTION;
+ } else {
+ portstatus = status;
}
- portstatus = status;
}
- /* Return now if nothing is connected */
+ /* Disconnect any existing devices under this port */
+ if (hdev->children[port1-1])
+ usb_disconnect(&hdev->children[port1-1]);
+ clear_bit(port1, hub->change_bits);
+
+ /* Return now if debouncing failed or nothing is connected */
if (!(portstatus & USB_PORT_STAT_CONNECTION)) {
/* maybe switch power back on (e.g. root hub was reset) */
