diff options
author | Ming Lei <ming.lei@canonical.com> | 2012-10-24 11:59:25 +0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-10-25 11:45:32 -0700 |
commit | 596d789a211d134dc5f94d1e5957248c204ef850 (patch) | |
tree | 6ffb0552cde7a5d607119251a337d66c583a9362 /drivers/usb/core | |
parent | e6f30deafe61179df048ac9040fe2bdf73a996c3 (diff) |
USB: set hub's default autosuspend delay as 0
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@rowland.harvard.edu>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/core')
-rw-r--r-- | drivers/usb/core/hub.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index ff86355d0df..43ce1467f8c 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1614,6 +1614,41 @@ 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); |