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>

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>
Alan Stern · Greg Kroah-Hartman
1 parent d58b4bcc6d
Showing 5 changed files with 101 additions and 61 deletions Side-by-side Diff
drivers/usb/host/ehci-hcd.c
drivers/usb/host/ehci-pci.c
drivers/usb/host/ehci-sched.c
drivers/usb/host/ehci-timer.c
drivers/usb/host/ehci.h
@@ -546,7 +546,7 @@
 	 */
 	if (ehci->rh_state == EHCI_RH_RUNNING &&
 			(ehci->async->qh_next.ptr != NULL ||
-			 ehci->periodic_sched != 0))
+			 ehci->periodic_count != 0))
 		timer_action (ehci, TIMER_IO_WATCHDOG);
 }
  
@@ -104,10 +104,6 @@
 		break;
 	case PCI_VENDOR_ID_INTEL:
 		ehci->fs_i_thresh = 1;
-		if (pdev->device == 0x27cc) {
-			ehci->broken_periodic = 1;
-			ehci_info(ehci, "using broken periodic workaround\n");
-		}
 		if (pdev->device == PCI_DEVICE_ID_INTEL_CE4100_USB)
 			hcd->has_tt = 1;
 		break;
@@ -481,67 +481,26 @@
  
 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;
-	}
+	/* Stop waiting to turn off the periodic schedule */
+	ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_DISABLE_PERIODIC);
  
-	ehci->command |= CMD_PSE;
-	ehci_writel(ehci, ehci->command, &ehci->regs->command);
-	/* posted write ... PSS happens later */
-
-	/* 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);
+	ehci->next_uframe = -1;		/* the periodic schedule is empty */
  
-		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;
+	/* Don't turn off the schedule until PSS is 1 */
+	ehci_poll_PSS(ehci);
 	return 0;
 }
  
@@ -650,8 +609,7 @@
 	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 @@
 			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 @@
  
 			/* 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 @@
 			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);
@@ -16,6 +16,28 @@
  
 /*-------------------------------------------------------------------------*/
  
+/* Set a bit in the USBCMD register */
+static void ehci_set_command_bit(struct ehci_hcd *ehci, u32 bit)
+{
+	ehci->command |= bit;
+	ehci_writel(ehci, ehci->command, &ehci->regs->command);
+
+	/* unblock posted write */
+	ehci_readl(ehci, &ehci->regs->command);
+}
+
+/* Clear a bit in the USBCMD register */
+static void ehci_clear_command_bit(struct ehci_hcd *ehci, u32 bit)
+{
+	ehci->command &= ~bit;
+	ehci_writel(ehci, ehci->command, &ehci->regs->command);
+
+	/* unblock posted write */
+	ehci_readl(ehci, &ehci->regs->command);
+}
+
+/*-------------------------------------------------------------------------*/
+
 /*
  * EHCI timer support...  Now using hrtimers.
  *
@@ -45,6 +67,8 @@
  * the event types indexed by enum ehci_hrtimer_event in ehci.h.
  */
 static unsigned event_delays_ns[] = {
+	1 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_POLL_PSS */
+	10 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_DISABLE_PERIODIC */
 };
  
 /* Enable a pending hrtimer event */
  
@@ -67,12 +91,68 @@
 }
  
  
+/* Poll the STS_PSS status bit; see when it agrees with CMD_PSE */
+static void ehci_poll_PSS(struct ehci_hcd *ehci)
+{
+	unsigned	actual, want;
+
+	/* Don't do anything if the controller isn't running (e.g., died) */
+	if (ehci->rh_state != EHCI_RH_RUNNING)
+		return;
+
+	want = (ehci->command & CMD_PSE) ? STS_PSS : 0;
+	actual = ehci_readl(ehci, &ehci->regs->status) & STS_PSS;
+
+	if (want != actual) {
+
+		/* Poll again later, but give up after about 20 ms */
+		if (ehci->PSS_poll_count++ < 20) {
+			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
+			return;
+		}
+		ehci_warn(ehci, "Waited too long for the periodic schedule status, giving up\n");
+	}
+	ehci->PSS_poll_count = 0;
+
+	/* The status is up-to-date; restart or stop the schedule as needed */
+	if (want == 0) {	/* Stopped */
+		free_cached_lists(ehci);
+		if (ehci->periodic_count > 0) {
+
+			/* make sure ehci_work scans these */
+			ehci->next_uframe = ehci_read_frame_index(ehci)
+					& ((ehci->periodic_size << 3) - 1);
+			ehci_set_command_bit(ehci, CMD_PSE);
+		}
+
+	} else {		/* Running */
+		if (ehci->periodic_count == 0) {
+
+			/* Turn off the schedule after a while */
+			ehci_enable_event(ehci, EHCI_HRTIMER_DISABLE_PERIODIC,
+					true);
+		}
+	}
+}
+
+/* Turn off the periodic schedule after a brief delay */
+static void ehci_disable_PSE(struct ehci_hcd *ehci)
+{
+	ehci_clear_command_bit(ehci, CMD_PSE);
+
+	/* Poll to see when it actually stops */
+	ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
+}
+
+
 /*
  * Handler functions for the hrtimer event types.
  * Keep this array in the same order as the event types indexed by
  * enum ehci_hrtimer_event in ehci.h.
  */
 static void (*event_handlers[])(struct ehci_hcd *) = {
+	ehci_poll_PSS,			/* EHCI_HRTIMER_POLL_PSS */
+	ehci_disable_PSE,		/* EHCI_HRTIMER_DISABLE_PERIODIC */
 };
  
 static enum hrtimer_restart ehci_hrtimer_func(struct hrtimer *t)
@@ -79,6 +79,8 @@
  * ehci-timer.c) in parallel with this list.
  */
 enum ehci_hrtimer_event {
+	EHCI_HRTIMER_POLL_PSS,		/* Poll for periodic schedule off */
+	EHCI_HRTIMER_DISABLE_PERIODIC,	/* Wait to disable periodic sched */
 	EHCI_HRTIMER_NUM_EVENTS		/* Must come last */
 };
 #define EHCI_HRTIMER_NO_EVENT	99
@@ -90,6 +92,8 @@
 	ktime_t			hr_timeouts[EHCI_HRTIMER_NUM_EVENTS];
 	struct hrtimer		hrtimer;
  
+	int			PSS_poll_count;
+
 	/* glue to PCI and HCD framework */
 	struct ehci_caps __iomem *caps;
 	struct ehci_regs __iomem *regs;
@@ -116,7 +120,7 @@
  
 	union ehci_shadow	*pshadow;	/* mirror hw periodic table */
 	int			next_uframe;	/* scan periodic, start here */
-	unsigned		periodic_sched;	/* periodic activity count */
+	unsigned		periodic_count;	/* periodic activity count */
 	unsigned		uframe_periodic_max; /* max periodic time per uframe */
  
  
@@ -165,7 +169,6 @@
 	unsigned		big_endian_capbase:1;
 	unsigned		has_amcc_usb23:1;
 	unsigned		need_io_watchdog:1;
-	unsigned		broken_periodic:1;
 	unsigned		amd_pll_fix:1;
 	unsigned		fs_i_thresh:1;	/* Intel iso scheduling */
 	unsigned		use_dummy_qh:1;	/* AMD Frame List table quirk*/
...	...	@@ -546,7 +546,7 @@
546	546	*/
547	547	if (ehci->rh_state == EHCI_RH_RUNNING &&
548	548	(ehci->async->qh_next.ptr != NULL \|\|
549		- ehci->periodic_sched != 0))
	549	+ ehci->periodic_count != 0))
550	550	timer_action (ehci, TIMER_IO_WATCHDOG);
551	551	}
552	552
...	...	@@ -104,10 +104,6 @@
104	104	break;
105	105	case PCI_VENDOR_ID_INTEL:
106	106	ehci->fs_i_thresh = 1;
107		- if (pdev->device == 0x27cc) {
108		- ehci->broken_periodic = 1;
109		- ehci_info(ehci, "using broken periodic workaround\n");
110		- }
111	107	if (pdev->device == PCI_DEVICE_ID_INTEL_CE4100_USB)
112	108	hcd->has_tt = 1;
113	109	break;
...	...	@@ -481,67 +481,26 @@
481	481
482	482	static int enable_periodic (struct ehci_hcd *ehci)
483	483	{
484		- int status;
485		-
486		- if (ehci->periodic_sched++)
	484	+ if (ehci->periodic_count++)
487	485	return 0;
488	486
489		- /* did clearing PSE did take effect yet?
490		- * takes effect only at frame boundaries...
491		- */
492		- status = handshake_on_error_set_halt(ehci, &ehci->regs->status,
493		- STS_PSS, 0, 9 * 125);
494		- if (status) {
495		- usb_hc_died(ehci_to_hcd(ehci));
496		- return status;
497		- }
	487	+ /* Stop waiting to turn off the periodic schedule */
	488	+ ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_DISABLE_PERIODIC);
498	489
499		- ehci->command \|= CMD_PSE;
500		- ehci_writel(ehci, ehci->command, &ehci->regs->command);
501		- /* posted write ... PSS happens later */
502		-
503		- /* make sure ehci_work scans these */
504		- ehci->next_uframe = ehci_read_frame_index(ehci)
505		- % (ehci->periodic_size << 3);
506		- if (unlikely(ehci->broken_periodic))
507		- ehci->last_periodic_enable = ktime_get_real();
	490	+ /* Don't start the schedule until PSS is 0 */
	491	+ ehci_poll_PSS(ehci);
508	492	return 0;
509	493	}
510	494
511	495	static int disable_periodic (struct ehci_hcd *ehci)
512	496	{
513		- int status;
514		-
515		- if (--ehci->periodic_sched)
	497	+ if (--ehci->periodic_count)
516	498	return 0;
517	499
518		- if (unlikely(ehci->broken_periodic)) {
519		- /* delay experimentally determined */
520		- ktime_t safe = ktime_add_us(ehci->last_periodic_enable, 1000);
521		- ktime_t now = ktime_get_real();
522		- s64 delay = ktime_us_delta(safe, now);
	500	+ ehci->next_uframe = -1; /* the periodic schedule is empty */
523	501
524		- if (unlikely(delay > 0))
525		- udelay(delay);
526		- }
527		-
528		- /* did setting PSE not take effect yet?
529		- * takes effect only at frame boundaries...
530		- */
531		- status = handshake_on_error_set_halt(ehci, &ehci->regs->status,
532		- STS_PSS, STS_PSS, 9 * 125);
533		- if (status) {
534		- usb_hc_died(ehci_to_hcd(ehci));
535		- return status;
536		- }
537		-
538		- ehci->command &= ~CMD_PSE;
539		- ehci_writel(ehci, ehci->command, &ehci->regs->command);
540		- /* posted write ... */
541		-
542		- free_cached_lists(ehci);
543		-
544		- ehci->next_uframe = -1;
	502	+ /* Don't turn off the schedule until PSS is 1 */
	503	+ ehci_poll_PSS(ehci);
545	504	return 0;
546	505	}
547	506
...	...	@@ -650,8 +609,7 @@
650	609	qh->qh_state = QH_STATE_UNLINK;
651	610	qh->qh_next.ptr = NULL;
652	611
653		- /* maybe turn off periodic schedule */
654		- return disable_periodic(ehci);
	612	+ return 0;
655	613	}
656	614
657	615	static void intr_deschedule (struct ehci_hcd ehci, struct ehci_qh qh)
...	...	@@ -706,6 +664,9 @@
706	664	ehci_err(ehci, "can't reschedule qh %p, err %d\n",
707	665	qh, rc);
708	666	}
	667	+
	668	+ /* maybe turn off periodic schedule */
	669	+ disable_periodic(ehci);
709	670	}
710	671
711	672	/-------------------------------------------------------------------------/
...	...	@@ -2447,7 +2408,7 @@
2447	2408
2448	2409	/* assume completion callbacks modify the queue */
2449	2410	if (unlikely (modified)) {
2450		- if (likely(ehci->periodic_sched > 0))
	2411	+ if (likely(ehci->periodic_count > 0))
2451	2412	goto restart;
2452	2413	/* short-circuit this scan */
2453	2414	now_uframe = clock;
...	...	@@ -2476,7 +2437,7 @@
2476	2437	unsigned now;
2477	2438
2478	2439	if (ehci->rh_state < EHCI_RH_RUNNING
2479		- \|\| ehci->periodic_sched == 0)
	2440	+ \|\| ehci->periodic_count == 0)
2480	2441	break;
2481	2442	ehci->next_uframe = now_uframe;
2482	2443	now = ehci_read_frame_index(ehci) & (mod - 1);
...	...	@@ -16,6 +16,28 @@
16	16
17	17	/-------------------------------------------------------------------------/
18	18
	19	+/* Set a bit in the USBCMD register */
	20	+static void ehci_set_command_bit(struct ehci_hcd *ehci, u32 bit)
	21	+{
	22	+ ehci->command \|= bit;
	23	+ ehci_writel(ehci, ehci->command, &ehci->regs->command);
	24	+
	25	+ /* unblock posted write */
	26	+ ehci_readl(ehci, &ehci->regs->command);
	27	+}
	28	+
	29	+/* Clear a bit in the USBCMD register */
	30	+static void ehci_clear_command_bit(struct ehci_hcd *ehci, u32 bit)
	31	+{
	32	+ ehci->command &= ~bit;
	33	+ ehci_writel(ehci, ehci->command, &ehci->regs->command);
	34	+
	35	+ /* unblock posted write */
	36	+ ehci_readl(ehci, &ehci->regs->command);
	37	+}
	38	+
	39	+/-------------------------------------------------------------------------/
	40	+
19	41	/*
20	42	* EHCI timer support... Now using hrtimers.
21	43	*
...	...	@@ -45,6 +67,8 @@
45	67	* the event types indexed by enum ehci_hrtimer_event in ehci.h.
46	68	*/
47	69	static unsigned event_delays_ns[] = {
	70	+ 1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_PSS */
	71	+ 10 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_PERIODIC */
48	72	};
49	73
50	74	/* Enable a pending hrtimer event */
51	75
...	...	@@ -67,12 +91,68 @@
67	91	}
68	92
69	93
	94	+/* Poll the STS_PSS status bit; see when it agrees with CMD_PSE */
	95	+static void ehci_poll_PSS(struct ehci_hcd *ehci)
	96	+{
	97	+ unsigned actual, want;
	98	+
	99	+ /* Don't do anything if the controller isn't running (e.g., died) */
	100	+ if (ehci->rh_state != EHCI_RH_RUNNING)
	101	+ return;
	102	+
	103	+ want = (ehci->command & CMD_PSE) ? STS_PSS : 0;
	104	+ actual = ehci_readl(ehci, &ehci->regs->status) & STS_PSS;
	105	+
	106	+ if (want != actual) {
	107	+
	108	+ /* Poll again later, but give up after about 20 ms */
	109	+ if (ehci->PSS_poll_count++ < 20) {
	110	+ ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
	111	+ return;
	112	+ }
	113	+ ehci_warn(ehci, "Waited too long for the periodic schedule status, giving up\n");
	114	+ }
	115	+ ehci->PSS_poll_count = 0;
	116	+
	117	+ /* The status is up-to-date; restart or stop the schedule as needed */
	118	+ if (want == 0) { /* Stopped */
	119	+ free_cached_lists(ehci);
	120	+ if (ehci->periodic_count > 0) {
	121	+
	122	+ /* make sure ehci_work scans these */
	123	+ ehci->next_uframe = ehci_read_frame_index(ehci)
	124	+ & ((ehci->periodic_size << 3) - 1);
	125	+ ehci_set_command_bit(ehci, CMD_PSE);
	126	+ }
	127	+
	128	+ } else { /* Running */
	129	+ if (ehci->periodic_count == 0) {
	130	+
	131	+ /* Turn off the schedule after a while */
	132	+ ehci_enable_event(ehci, EHCI_HRTIMER_DISABLE_PERIODIC,
	133	+ true);
	134	+ }
	135	+ }
	136	+}
	137	+
	138	+/* Turn off the periodic schedule after a brief delay */
	139	+static void ehci_disable_PSE(struct ehci_hcd *ehci)
	140	+{
	141	+ ehci_clear_command_bit(ehci, CMD_PSE);
	142	+
	143	+ /* Poll to see when it actually stops */
	144	+ ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
	145	+}
	146	+
	147	+
70	148	/*
71	149	* Handler functions for the hrtimer event types.
72	150	* Keep this array in the same order as the event types indexed by
73	151	* enum ehci_hrtimer_event in ehci.h.
74	152	*/
75	153	static void (event_handlers[])(struct ehci_hcd ) = {
	154	+ ehci_poll_PSS, /* EHCI_HRTIMER_POLL_PSS */
	155	+ ehci_disable_PSE, /* EHCI_HRTIMER_DISABLE_PERIODIC */
76	156	};
77	157
78	158	static enum hrtimer_restart ehci_hrtimer_func(struct hrtimer *t)
...	...	@@ -79,6 +79,8 @@
79	79	* ehci-timer.c) in parallel with this list.
80	80	*/
81	81	enum ehci_hrtimer_event {
	82	+ EHCI_HRTIMER_POLL_PSS, /* Poll for periodic schedule off */
	83	+ EHCI_HRTIMER_DISABLE_PERIODIC, /* Wait to disable periodic sched */
82	84	EHCI_HRTIMER_NUM_EVENTS /* Must come last */
83	85	};
84	86	#define EHCI_HRTIMER_NO_EVENT 99
...	...	@@ -90,6 +92,8 @@
90	92	ktime_t hr_timeouts[EHCI_HRTIMER_NUM_EVENTS];
91	93	struct hrtimer hrtimer;
92	94
	95	+ int PSS_poll_count;
	96	+
93	97	/* glue to PCI and HCD framework */
94	98	struct ehci_caps __iomem *caps;
95	99	struct ehci_regs __iomem *regs;
...	...	@@ -116,7 +120,7 @@
116	120
117	121	union ehci_shadow pshadow; / mirror hw periodic table */
118	122	int next_uframe; /* scan periodic, start here */
119		- unsigned periodic_sched; /* periodic activity count */
	123	+ unsigned periodic_count; /* periodic activity count */
120	124	unsigned uframe_periodic_max; /* max periodic time per uframe */
121	125
122	126
...	...	@@ -165,7 +169,6 @@
165	169	unsigned big_endian_capbase:1;
166	170	unsigned has_amcc_usb23:1;
167	171	unsigned need_io_watchdog:1;
168		- unsigned broken_periodic:1;
169	172	unsigned amd_pll_fix:1;
170	173	unsigned fs_i_thresh:1; /* Intel iso scheduling */
171	174	unsigned use_dummy_qh:1; /* AMD Frame List table quirk*/