xhci(4) and ehci(4) are scheduling continuous isoc transfers. For that
we have implemented a kind of workaround, which checks whether
usbd_start_next() is calling in between and try to start an transfer
which is still in progress.
NetBSD has introduced a variable called 'serialise' for the pipe,
with which one can control whether to skip the usbd_start_next()
call at all, and therefore schedule continuous transfers without
the need for explicit checks whether the transfer is still in progress.
By default we set 'serialise' to 1 in pipe initialization, so that the
default behavior remains to call usbd_start_next() after a completed
transfer. If we want to schedule continuous transfers, we overwrite
'serialise' with 0 in the HC driver.
I like the approach and I think it's more straight forward than what
we do today. It will also allow to easily implement continuous
transfers in other HC drivers, i.e. in dwctwo(4).
Comments? OKs?
Index: sys/dev/usb/ehci.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/ehci.c,v
retrieving revision 1.219
diff -u -p -u -p -r1.219 ehci.c
--- sys/dev/usb/ehci.c 12 Apr 2022 19:41:11 -0000 1.219
+++ sys/dev/usb/ehci.c 29 Aug 2022 15:40:54 -0000
@@ -1505,6 +1505,7 @@ ehci_open(struct usbd_pipe *pipe)
case EHCI_QH_SPEED_HIGH:
case EHCI_QH_SPEED_FULL:
pipe->methods = &ehci_device_isoc_methods;
+ pipe->serialise = 0;
break;
case EHCI_QH_SPEED_LOW:
default:
@@ -3247,7 +3248,7 @@ ehci_device_isoc_transfer(struct usbd_xf
usbd_status err;
err = usb_insert_transfer(xfer);
- if (err && err != USBD_IN_PROGRESS)
+ if (err)
return (err);
return (ehci_device_isoc_start(xfer));
@@ -3267,15 +3268,6 @@ ehci_device_isoc_start(struct usbd_xfer
KASSERT(!(xfer->rqflags & URQ_REQUEST));
KASSERT(ival > 0 && ival <= 16);
-
- /*
- * To allow continuous transfers, above we start all transfers
- * immediately. However, we're still going to get usbd_start_next call
- * this when another xfer completes. So, check if this is already
- * in progress or not
- */
- if (ex->itdstart != NULL)
- return (USBD_IN_PROGRESS);
if (sc->sc_bus.dying)
return (USBD_IOERROR);
Index: sys/dev/usb/usb_subr.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/usb_subr.c,v
retrieving revision 1.158
diff -u -p -u -p -r1.158 usb_subr.c
--- sys/dev/usb/usb_subr.c 16 Feb 2022 06:23:42 -0000 1.158
+++ sys/dev/usb/usb_subr.c 29 Aug 2022 15:40:54 -0000
@@ -793,6 +793,7 @@ usbd_setup_pipe(struct usbd_device *dev,
p->endpoint = ep;
ep->refcnt++;
p->interval = ival;
+ p->serialise = 1;
SIMPLEQ_INIT(&p->queue);
err = dev->bus->methods->open_pipe(p);
if (err) {
Index: sys/dev/usb/usbdi.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/usbdi.c,v
retrieving revision 1.110
diff -u -p -u -p -r1.110 usbdi.c
--- sys/dev/usb/usbdi.c 3 Feb 2021 11:34:24 -0000 1.110
+++ sys/dev/usb/usbdi.c 29 Aug 2022 15:40:54 -0000
@@ -822,7 +822,7 @@ usb_transfer_complete(struct usbd_xfer *
status == USBD_TIMEOUT) &&
pipe->iface != NULL) /* not control pipe */
pipe->running = 0;
- else
+ else if (pipe->serialise)
usbd_start_next(pipe);
}
}
@@ -845,7 +845,7 @@ usb_insert_transfer(struct usbd_xfer *xf
#endif
s = splusb();
SIMPLEQ_INSERT_TAIL(&pipe->queue, xfer, next);
- if (pipe->running)
+ if (pipe->running && pipe->serialise)
err = USBD_IN_PROGRESS;
else {
pipe->running = 1;
Index: sys/dev/usb/usbdivar.h
===================================================================
RCS file: /cvs/src/sys/dev/usb/usbdivar.h,v
retrieving revision 1.82
diff -u -p -u -p -r1.82 usbdivar.h
--- sys/dev/usb/usbdivar.h 12 Apr 2022 19:41:11 -0000 1.82
+++ sys/dev/usb/usbdivar.h 29 Aug 2022 15:40:55 -0000
@@ -186,6 +186,7 @@ struct usbd_pipe {
size_t pipe_size;
char running;
char aborting;
+ char serialise;
SIMPLEQ_HEAD(, usbd_xfer) queue;
LIST_ENTRY(usbd_pipe) next;
Index: sys/dev/usb/xhci.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/xhci.c,v
retrieving revision 1.126
diff -u -p -u -p -r1.126 xhci.c
--- sys/dev/usb/xhci.c 15 Jul 2022 07:52:06 -0000 1.126
+++ sys/dev/usb/xhci.c 29 Aug 2022 15:40:55 -0000
@@ -1224,6 +1224,7 @@ xhci_pipe_open(struct usbd_pipe *pipe)
break;
case UE_ISOCHRONOUS:
pipe->methods = &xhci_device_isoc_methods;
+ pipe->serialise = 0;
break;
case UE_BULK:
pipe->methods = &xhci_device_bulk_methods;
@@ -3075,7 +3076,7 @@ xhci_device_isoc_transfer(struct usbd_xf
usbd_status err;
err = usb_insert_transfer(xfer);
- if (err && err != USBD_IN_PROGRESS)
+ if (err)
return (err);
return (xhci_device_isoc_start(xfer));
@@ -3086,7 +3087,6 @@ xhci_device_isoc_start(struct usbd_xfer
{
struct xhci_softc *sc = (struct xhci_softc *)xfer->device->bus;
struct xhci_pipe *xp = (struct xhci_pipe *)xfer->pipe;
- struct xhci_xfer *xx = (struct xhci_xfer *)xfer;
struct xhci_trb *trb0, *trb;
uint32_t len, remain, flags;
uint64_t paddr;
@@ -3095,15 +3095,6 @@ xhci_device_isoc_start(struct usbd_xfer
uint8_t toggle;
KASSERT(!(xfer->rqflags & URQ_REQUEST));
-
- /*
- * To allow continuous transfers, above we start all transfers
- * immediately. However, we're still going to get usbd_start_next call
- * this when another xfer completes. So, check if this is already
- * in progress or not
- */
- if (xx->ntrb > 0)
- return (USBD_IN_PROGRESS);
if (sc->sc_bus.dying || xp->halted)
return (USBD_IOERROR);
