This patch sets hub device's default autosuspend delay as 0 to speedup bus suspend, see comments in code for details. Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> --- drivers/usb/core/hub.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index b3205b0..522ad57 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1613,6 +1613,41 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id) desc = intf->cur_altsetting; hdev = interface_to_usbdev(intf); + /* + * Set default autosuspend delay as 0 to speedup bus suspend, + * based on the below considerations: + * + * - Unlike other drivers, the hub driver does not rely on the + * autosuspend delay to provide enough time to handle a wakeup + * event, and the submitted status URB is just to check future + * change on hub downstream ports, so it is safe to do it. + * + * - The patch might cause one or more auto supend/resume for + * below very rare devices when they are plugged into hub + * first time: + * + * devices having trouble initializing, and disconnect + * themselves from the bus and then reconnect a second + * or so later + * + * devices just for downloading firmware, and disconnects + * themselves after completing it + * + * For these quite rare devices, their drivers may change the + * autosuspend delay of their parent hub in the probe() to one + * appropriate value to avoid the subtle problem if someone + * does care it. + * + * - The patch may cause one or more auto suspend/resume on + * hub during running 'lsusb', but it is probably too + * infrequent to worry about. + * + * - Change autosuspend delay of hub can avoid unnecessary auto + * suspend timer for hub, also may decrease power consumption + * of USB bus. + */ + pm_runtime_set_autosuspend_delay(&hdev->dev, 0); + /* Hubs have proper suspend/resume support. */ usb_enable_autosuspend(hdev); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
