USB: EHCI: stagger frames for interrupt transfers (68335e81) · Commits · 戴 / test

This patch (as1243) tries to improve ehci-hcd's scheduling of interrupt transfers. Instead of trying to cram all transfers with the same period into the same frame, the new code will spread the transfers out among lots of different frames. This should reduce the periodic schedule load in any one frame -- some host controllers have trouble when there's too much work to do. A more thorough approach would stagger the uframe values as well. But this is enough to make a big improvement. Signed-off-by:

Alan Stern <stern@rowland.harvard.edu> Tested-by:

Dwayne Fontenot <dwayne.fontenot@att.net> Cc: David Brownell <david-b@pacbell.net> Signed-off-by:

Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-sched.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -760,8 +760,10 @@ static int qh_schedule(struct ehci_hcd ehci, struct ehci_qh qh)
		if (status) {
		/* "normal" case, uframing flexible except with splits */
		if (qh->period) {
		frame = qh->period - 1;
		do {
		int i;

		for (i = qh->period; status && i > 0; --i) {
		frame = ++ehci->random_frame % qh->period;
		for (uframe = 0; uframe < 8; uframe++) {
		status = check_intr_schedule (ehci,
		frame, uframe, qh,
		@@ -769,7 +771,7 @@ static int qh_schedule(struct ehci_hcd ehci, struct ehci_qh qh)
		if (status == 0)
		break;
		}
		} while (status && frame--);
		}

		/* qh->period == 0 means every uframe */
		} else {

drivers/usb/host/ehci.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -116,6 +116,7 @@ struct ehci_hcd { /* one per controller */
		struct timer_list watchdog;
		unsigned long actions;
		unsigned stamp;
		unsigned random_frame;
		unsigned long next_statechange;
		u32 command;

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