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Commit 01cd0819 authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Greg Kroah-Hartman
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USB: Patch to align the various USB timers to fire at the same time 



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: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent fc4cbd75

drivers/usb/core/hcd.c

+6 −4
Original line number Diff line number Diff line
@@ -582,10 +582,12 @@ void usb_hcd_poll_rh_status(struct usb_hcd *hcd) 
	}



	/* 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_hcd *hcd, struct urb *urb) 
		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)