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Commit bccbefaa authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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USB: EHCI: simplify remainder computations 



This patch (as1406) adds a micro-optimization to ehci-hcd's scheduling
code.  Instead of computing remainders with respect to the schedule
length, use bitwise-and (which is quicker).  We know that the schedule
length will always be a power of two, but the compiler doesn't have
this information.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
CC: David Brownell <david-b@pacbell.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent ae68a83b

drivers/usb/host/ehci-sched.c

+15 −14
Original line number Diff line number Diff line
@@ -1417,7 +1417,7 @@ iso_stream_schedule ( 
	if (!stream->highspeed)

		period <<= 3;



	now = ehci_readl(ehci, &ehci->regs->frame_index) % mod;

	now = ehci_readl(ehci, &ehci->regs->frame_index) & (mod - 1);



	/* Typical case: reuse current schedule, stream is still active.

	 * Hopefully there are no gaps from the host falling behind
@@ -1461,7 +1461,7 @@ iso_stream_schedule ( 
	 * jump until after the queue is primed.

	 */

	start = SCHEDULE_SLOP + (now & ~0x07);

	start %= mod;

	start &= mod - 1;

	stream->next_uframe = start;



	/* NOTE:  assumes URB_ISO_ASAP, to limit complexity/bugs */
@@ -1483,7 +1483,7 @@ iso_stream_schedule ( 


		/* schedule it here if there's enough bandwidth */

		if (enough_space) {

			stream->next_uframe = start % mod;

			stream->next_uframe = start & (mod - 1);

			goto ready;

		}

	}
@@ -1599,7 +1599,7 @@ itd_link_urb ( 
	struct ehci_iso_sched	*iso_sched = urb->hcpriv;

	struct ehci_itd		*itd;



	next_uframe = stream->next_uframe % mod;

	next_uframe = stream->next_uframe & (mod - 1);



	if (unlikely (list_empty(&stream->td_list))) {

		ehci_to_hcd(ehci)->self.bandwidth_allocated
@@ -1637,13 +1637,13 @@ itd_link_urb ( 


		next_uframe += stream->interval;

		stream->depth += stream->interval;

		next_uframe %= mod;

		next_uframe &= mod - 1;

		packet++;



		/* link completed itds into the schedule */

		if (((next_uframe >> 3) != frame)

				|| packet == urb->number_of_packets) {

			itd_link (ehci, frame % ehci->periodic_size, itd);

			itd_link(ehci, frame & (ehci->periodic_size - 1), itd);

			itd = NULL;

		}

	}
@@ -2020,7 +2020,7 @@ sitd_link_urb ( 
			"sched devp %s ep%d%s-iso [%d] %dms/%04x\n",

			urb->dev->devpath, stream->bEndpointAddress & 0x0f,

			(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out",

			(next_uframe >> 3) % ehci->periodic_size,

			(next_uframe >> 3) & (ehci->periodic_size - 1),

			stream->interval, hc32_to_cpu(ehci, stream->splits));

		stream->start = jiffies;

	}
@@ -2043,13 +2043,13 @@ sitd_link_urb ( 
		sitd->urb = urb;



		sitd_patch(ehci, stream, sitd, sched, packet);

		sitd_link (ehci, (next_uframe >> 3) % ehci->periodic_size,

		sitd_link(ehci, (next_uframe >> 3) & (ehci->periodic_size - 1),

				sitd);



		next_uframe += stream->interval << 3;

		stream->depth += stream->interval << 3;

	}

	stream->next_uframe = next_uframe % mod;

	stream->next_uframe = next_uframe & (mod - 1);



	/* don't need that schedule data any more */

	iso_sched_free (stream, sched);
@@ -2258,7 +2258,7 @@ scan_periodic (struct ehci_hcd *ehci) 
	now_uframe = ehci->next_uframe;

	if (HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {

		clock = ehci_readl(ehci, &ehci->regs->frame_index);

		clock_frame = (clock >> 3) % ehci->periodic_size;

		clock_frame = (clock >> 3) & (ehci->periodic_size - 1);

	} else  {

		clock = now_uframe + mod - 1;

		clock_frame = -1;
@@ -2267,7 +2267,7 @@ scan_periodic (struct ehci_hcd *ehci) 
		free_cached_lists(ehci);

		ehci->clock_frame = clock_frame;

	}

	clock %= mod;

	clock &= mod - 1;

	clock_frame = clock >> 3;



	for (;;) {
@@ -2356,7 +2356,7 @@ restart: 
				 * frame is current.

				 */

				if (((frame == clock_frame) ||

				     (((frame + 1) % ehci->periodic_size)

				     (((frame + 1) & (ehci->periodic_size - 1))

				      == clock_frame))

				    && live

				    && (q.sitd->hw_results &
@@ -2423,7 +2423,8 @@ restart: 
					|| ehci->periodic_sched == 0)

				break;

			ehci->next_uframe = now_uframe;

			now = ehci_readl(ehci, &ehci->regs->frame_index) % mod;

			now = ehci_readl(ehci, &ehci->regs->frame_index) &

					(mod - 1);

			if (now_uframe == now)

				break;
@@ -2436,7 +2437,7 @@ restart: 
			}

		} else {

			now_uframe++;

			now_uframe %= mod;

			now_uframe &= mod - 1;

		}

	}

}