USB: EHCI: use hrtimer for the periodic schedule

This patch (as1573) adds hrtimer support for managing ehci-hcd's
periodic schedule.  There are two issues to deal with.

First, the schedule's state (on or off) must not be changed until the
hardware status has caught up with the current command.  This is
handled by an hrtimer event that polls at 1-ms intervals to see when
the Periodic Schedule Status (PSS) flag matches the Periodic Schedule
Enable (PSE) value.

Second, the schedule should not be turned off as soon as it becomes
empty.  Turning the schedule on and off takes time, so we want to wait
until the schedule has been empty for a suitable period before turning
it off.  This is handled by an hrtimer event that gets set to expire
10 ms after the periodic schedule becomes empty.

The existing code polls (for up to 1125 us and with interrupts
disabled!) to check the status, and doesn't implement a delay before
turning off the schedule.  Furthermore, if the polling fails then the
driver decides that the controller has died.  This has caused problems
for several people; some controllers can take 10 ms or more to turn
off their periodic schedules.

This patch fixes these issues.  It also makes the "broken_periodic"
workaround unnecessary; there is no longer any danger of turning off
the periodic schedule after it has been on for less than 1 ms.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 54 deletions

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 3429b8a33c58..f5c15880c65a 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -481,67 +481,26 @@ static int tt_no_collision (
 
 static int enable_periodic (struct ehci_hcd *ehci)
 {
-	int	status;
-
-	if (ehci->periodic_sched++)
+	if (ehci->periodic_count++)
 		return 0;
 
-	/* did clearing PSE did take effect yet?
-	 * takes effect only at frame boundaries...
-	 */
-	status = handshake_on_error_set_halt(ehci, &ehci->regs->status,
-					     STS_PSS, 0, 9 * 125);
-	if (status) {
-		usb_hc_died(ehci_to_hcd(ehci));
-		return status;
-	}
-
-	ehci->command |= CMD_PSE;
-	ehci_writel(ehci, ehci->command, &ehci->regs->command);
-	/* posted write ... PSS happens later */
+	/* Stop waiting to turn off the periodic schedule */
+	ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_DISABLE_PERIODIC);
 
-	/* make sure ehci_work scans these */
-	ehci->next_uframe = ehci_read_frame_index(ehci)
-		% (ehci->periodic_size << 3);
-	if (unlikely(ehci->broken_periodic))
-		ehci->last_periodic_enable = ktime_get_real();
+	/* Don't start the schedule until PSS is 0 */
+	ehci_poll_PSS(ehci);
 	return 0;
 }
 
 static int disable_periodic (struct ehci_hcd *ehci)
 {
-	int	status;
-
-	if (--ehci->periodic_sched)
+	if (--ehci->periodic_count)
 		return 0;
 
-	if (unlikely(ehci->broken_periodic)) {
-		/* delay experimentally determined */
-		ktime_t safe = ktime_add_us(ehci->last_periodic_enable, 1000);
-		ktime_t now = ktime_get_real();
-		s64 delay = ktime_us_delta(safe, now);
-
-		if (unlikely(delay > 0))
-			udelay(delay);
-	}
-
-	/* did setting PSE not take effect yet?
-	 * takes effect only at frame boundaries...
-	 */
-	status = handshake_on_error_set_halt(ehci, &ehci->regs->status,
-					     STS_PSS, STS_PSS, 9 * 125);
-	if (status) {
-		usb_hc_died(ehci_to_hcd(ehci));
-		return status;
-	}
-
-	ehci->command &= ~CMD_PSE;
-	ehci_writel(ehci, ehci->command, &ehci->regs->command);
-	/* posted write ... */
-
-	free_cached_lists(ehci);
+	ehci->next_uframe = -1;		/* the periodic schedule is empty */
 
-	ehci->next_uframe = -1;
+	/* Don't turn off the schedule until PSS is 1 */
+	ehci_poll_PSS(ehci);
 	return 0;
 }
 
@@ -650,8 +609,7 @@ static int qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
 	qh->qh_state = QH_STATE_UNLINK;
 	qh->qh_next.ptr = NULL;
 
-	/* maybe turn off periodic schedule */
-	return disable_periodic(ehci);
+	return 0;
 }
 
 static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
@@ -706,6 +664,9 @@ static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
 			ehci_err(ehci, "can't reschedule qh %p, err %d\n",
 					qh, rc);
 	}
+
+	/* maybe turn off periodic schedule */
+	disable_periodic(ehci);
 }
 
 /*-------------------------------------------------------------------------*/
@@ -2447,7 +2408,7 @@ restart:
 
 			/* assume completion callbacks modify the queue */
 			if (unlikely (modified)) {
-				if (likely(ehci->periodic_sched > 0))
+				if (likely(ehci->periodic_count > 0))
 					goto restart;
 				/* short-circuit this scan */
 				now_uframe = clock;
@@ -2476,7 +2437,7 @@ restart:
 			unsigned	now;
 
 			if (ehci->rh_state < EHCI_RH_RUNNING
-					|| ehci->periodic_sched == 0)
+					|| ehci->periodic_count == 0)
 				break;
 			ehci->next_uframe = now_uframe;
 			now = ehci_read_frame_index(ehci) & (mod - 1);