This patch (as1674) speeds up system sleep transitions by not
suspending each individual device on a USB-1.1 or USB-2 bus. The
devices will automatically go into suspend when their root hubs are
suspended (i.e., stop sending out Start-Of-Frame packets) -- this is
what the USB spec calls "global suspend".
Since this is what we do already when CONFIG_USB_SUSPEND isn't
enabled, it shouldn't cause any problems.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
CC: Peter Chen <peter.chen@xxxxxxxxxxxxx>
---
drivers/usb/core/hub.c | 30 +++++++++++++++++++++++-------
1 file changed, 23 insertions(+), 7 deletions(-)
Index: usb-3.9/drivers/usb/core/hub.c
===================================================================
--- usb-3.9.orig/drivers/usb/core/hub.c
+++ usb-3.9/drivers/usb/core/hub.c
@@ -2882,9 +2882,11 @@ static int usb_disable_function_remotewa
* Linux (2.6) currently has NO mechanisms to initiate that: no khubd
* timer, no SRP, no requests through sysfs.
*
- * If CONFIG_USB_SUSPEND isn't enabled, devices only really suspend when
- * the root hub for their bus goes into global suspend ... so we don't
- * (falsely) update the device power state to say it suspended.
+ * If CONFIG_USB_SUSPEND isn't enabled, non-SuperSpeed devices really get
+ * suspended only when their bus goes into global suspend (i.e., the root
+ * hub is suspended). Nevertheless, we change @udev->state to
+ * USB_STATE_SUSPENDED as this is the device's "logical" state. The actual
+ * upstream port setting is stored in @udev->port_is_suspended.
*
* Returns 0 on success, else negative errno.
*/
@@ -2895,6 +2897,7 @@ int usb_port_suspend(struct usb_device *
enum pm_qos_flags_status pm_qos_stat;
int port1 = udev->portnum;
int status;
+ bool really_suspend = true;
/* enable remote wakeup when appropriate; this lets the device
* wake up the upstream hub (including maybe the root hub).
@@ -2951,9 +2954,19 @@ int usb_port_suspend(struct usb_device *
/* see 7.1.7.6 */
if (hub_is_superspeed(hub->hdev))
status = hub_set_port_link_state(hub, port1, USB_SS_PORT_LS_U3);
- else
+ else if (PMSG_IS_AUTO(msg))
status = set_port_feature(hub->hdev, port1,
USB_PORT_FEAT_SUSPEND);
+ /*
+ * For system suspend, we do not need to enable the suspend feature
+ * on individual USB-2 ports. The devices will automatically go
+ * into suspend a few ms after the root hub stops sending packets.
+ * The USB 2.0 spec calls this "global suspend".
+ */
+ else {
+ really_suspend = false;
+ status = 0;
+ }
if (status) {
dev_dbg(hub->intfdev, "can't suspend port %d, status %d\n",
port1, status);
@@ -2989,8 +3002,10 @@ int usb_port_suspend(struct usb_device *
(PMSG_IS_AUTO(msg) ? "auto-" : ""),
udev->do_remote_wakeup);
usb_set_device_state(udev, USB_STATE_SUSPENDED);
- udev->port_is_suspended = 1;
- msleep(10);
+ if (really_suspend) {
+ udev->port_is_suspended = 1;
+ msleep(10);
+ }
}
/*
--
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