From SRS0+7d36af90c60d82e1d2f1+1367+infradead.org+arjan@pentafluge.srs.infradead.org Tue May 22 12:44:36 2007 From: Arjan van de Ven Date: Tue, 22 May 2007 12:42:56 -0700 Subject: USB: Patch to align the various USB timers to fire at the same time To: linux-usb-devel@lists.sourceforge.net Cc: gregkh@kroah.com Message-ID: <1179862976.5470.1.camel@laptopd505.fenrus.org> This patch modifies the USB regular 250ms timer to be "perfectly aligned" to the second and quarters thereof. This change is there to make sure that if you have multiple USB ports, the timers for all these ports will fire at the same time rather than all spread out. All spread out wakes the CPU up from power saving idle a lot more than needed... Signed-off-by: Arjan van de Ven Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hcd.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -582,10 +582,12 @@ void usb_hcd_poll_rh_status(struct usb_h } /* The USB 2.0 spec says 256 ms. This is close enough and won't - * exceed that limit if HZ is 100. */ + * exceed that limit if HZ is 100. The math is more clunky than + * maybe expected, this is to make sure that all timers for USB devices + * fire at the same time to give the CPU a break inbetween */ if (hcd->uses_new_polling ? hcd->poll_rh : (length == 0 && hcd->status_urb != NULL)) - mod_timer (&hcd->rh_timer, jiffies + msecs_to_jiffies(250)); + mod_timer (&hcd->rh_timer, (jiffies/(HZ/4) + 1) * (HZ/4)); } EXPORT_SYMBOL_GPL(usb_hcd_poll_rh_status); @@ -614,8 +616,8 @@ static int rh_queue_status (struct usb_h urb->hcpriv = hcd; /* indicate it's queued */ if (!hcd->uses_new_polling) - mod_timer (&hcd->rh_timer, jiffies + - msecs_to_jiffies(250)); + mod_timer (&hcd->rh_timer, + (jiffies/(HZ/4) + 1) * (HZ/4)); /* If a status change has already occurred, report it ASAP */ else if (hcd->poll_pending)