From 948fea37dcebfef8f0f2faf00930e7ec7e756e07 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Mon, 28 Apr 2008 11:07:07 -0400 Subject: USB: optimize port debouncing during hub activation This patch (as1082) makes a small optimization to the way the hub driver carries out port debouncing immediately after a hub is activated (i.e., initialized, reset, or resumed). If any port-change statuses are observed, the code will delay for a minimal debounce period -- thereby making a good start at debouncing all the ports at once. If this wasn't sufficient then khubd will debounce any port that still requires attention. But in most cases it should suffice; it's rare for a device to need more than a minimal debounce delay. (In the cases of hub initialization or reset even that is most likely not needed, since any devices plugged in at such times have probably been attached for a while.) Signed-off-by: Alan Stern Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hub.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) (limited to 'drivers/usb/core') diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 8ea095e5909..bc80168957b 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -130,6 +130,10 @@ MODULE_PARM_DESC(use_both_schemes, DECLARE_RWSEM(ehci_cf_port_reset_rwsem); EXPORT_SYMBOL_GPL(ehci_cf_port_reset_rwsem); +#define HUB_DEBOUNCE_TIMEOUT 1500 +#define HUB_DEBOUNCE_STEP 25 +#define HUB_DEBOUNCE_STABLE 100 + static inline char *portspeed(int portstatus) { @@ -643,6 +647,7 @@ static void hub_restart(struct usb_hub *hub, enum hub_activation_type type) { struct usb_device *hdev = hub->hdev; int port1; + bool need_debounce_delay = false; /* Check each port and set hub->change_bits to let khubd know * which ports need attention. @@ -673,6 +678,18 @@ static void hub_restart(struct usb_hub *hub, enum hub_activation_type type) portstatus &= ~USB_PORT_STAT_ENABLE; } + /* Clear status-change flags; we'll debounce later */ + if (portchange & USB_PORT_STAT_C_CONNECTION) { + need_debounce_delay = true; + clear_port_feature(hub->hdev, port1, + USB_PORT_FEAT_C_CONNECTION); + } + if (portchange & USB_PORT_STAT_C_ENABLE) { + need_debounce_delay = true; + clear_port_feature(hub->hdev, port1, + USB_PORT_FEAT_C_ENABLE); + } + if (!udev || udev->state == USB_STATE_NOTATTACHED) { /* Tell khubd to disconnect the device or * check for a new connection @@ -702,6 +719,16 @@ static void hub_restart(struct usb_hub *hub, enum hub_activation_type type) } } + /* If no port-status-change flags were set, we don't need any + * debouncing. If flags were set we can try to debounce the + * ports all at once right now, instead of letting khubd do them + * one at a time later on. + * + * If any port-status changes do occur during this delay, khubd + * will see them later and handle them normally. + */ + if (need_debounce_delay) + msleep(HUB_DEBOUNCE_STABLE); hub_activate(hub); } @@ -2211,11 +2238,6 @@ static inline int remote_wakeup(struct usb_device *udev) * every 25ms for transient disconnects. When the port status has been * unchanged for 100ms it returns the port status. */ - -#define HUB_DEBOUNCE_TIMEOUT 1500 -#define HUB_DEBOUNCE_STEP 25 -#define HUB_DEBOUNCE_STABLE 100 - static int hub_port_debounce(struct usb_hub *hub, int port1) { int ret; -- cgit v1.2.3-70-g09d2