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USB: EHCI: use hrtimer for async schedule

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This patch (as1576) adds hrtimer support for managing ehci-hcd's
async schedule.  Just as with the earlier change to the periodic
schedule management, two new hrtimer events take care of everything.

One event polls at 1-ms intervals to see when the Asynchronous
Schedule Status (ASS) flag matches the Asynchronous Schedule Enable
(ASE) value; the schedule's state must not be changed until it does.
The other event delays for 15 ms after the async schedule becomes
empty before turning it off.

The new events replace a busy-wait poll and a kernel timer usage.
They also replace the rather illogical method currently used for
indicating the async schedule should be turned off: attempting to
unlink the dedicated QH at the head of the async list.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2012-07-11 11:22:21 -04:00 • committed by Greg Kroah-Hartman
parent 9671cd7a91
commit 314466101c
4 changed files with 86 additions and 49 deletions
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13
drivers/usb/host/ehci-hcd.c
View file

@ -95,7 +95,6 @@ static const char hcd_name [] = "ehci_hcd";
#define EHCI_IAA_MSECS 10 /* arbitrary */
#define EHCI_IO_JIFFIES (HZ/10) /* io watchdog > irq_thresh */
#define EHCI_ASYNC_JIFFIES (HZ/20) /* async idle timeout */
#define EHCI_SHRINK_JIFFIES (DIV_ROUND_UP(HZ, 200) + 1)
/* 5-ms async qh unlink delay */
@ -137,7 +136,7 @@ timer_action(struct ehci_hcd *ehci, enum ehci_timer_action action)
* SHRINK were pending, OFF would never be requested.
*/
if (timer_pending(&ehci->watchdog)
&& ((BIT(TIMER_ASYNC_SHRINK) | BIT(TIMER_ASYNC_OFF))
&& (BIT(TIMER_ASYNC_SHRINK)
& ehci->actions))
return;
@ -150,9 +149,6 @@ timer_action(struct ehci_hcd *ehci, enum ehci_timer_action action)
return;
t = EHCI_IO_JIFFIES;
break;
case TIMER_ASYNC_OFF:
t = EHCI_ASYNC_JIFFIES;
break;
/* case TIMER_ASYNC_SHRINK: */
default:
t = EHCI_SHRINK_JIFFIES;
@ -376,10 +372,6 @@ static void ehci_watchdog(unsigned long param)
spin_lock_irqsave(&ehci->lock, flags);
/* stop async processing after it's idled a bit */
if (test_bit (TIMER_ASYNC_OFF, &ehci->actions))
start_unlink_async (ehci, ehci->async);
/* ehci could run by timer, without IRQs ... */
ehci_work (ehci);
@ -470,7 +462,8 @@ static void ehci_work (struct ehci_hcd *ehci)
if (ehci->scanning)
return;
ehci->scanning = 1;
scan_async (ehci);
if (ehci->async_count)
scan_async(ehci);
if (ehci->next_uframe != -1)
scan_periodic (ehci);
ehci->scanning = 0;