Work around a problem seen on VIA EHCI controllers where occasionally

an interrupt appears to occur before the transfer has been marked
as completed. This caused umass transfers to get stuck, especially
when writing large files. The workaround sets up a timer that
rechecks for missed completed transfers if some operations are still
pending. Other suggested workarounds, such as performing a PCI read
immediately after acknowledging the interrupts, do not appear to
help.

Obtained from:	OpenBSD

3 files changed, 38 insertions, 0 deletions

diff --git a/sys/dev/usb/ehci.c b/sys/dev/usb/ehci.c
index eeb47a4..5324c5e0 100644
--- a/sys/dev/usb/ehci.c
+++ b/sys/dev/usb/ehci.c
@@ -153,6 +153,7 @@ Static void		ehci_check_intr(ehci_softc_t *, struct ehci_xfer *);
 Static void		ehci_idone(struct ehci_xfer *);
 Static void		ehci_timeout(void *);
 Static void		ehci_timeout_task(void *);
+Static void		ehci_intrlist_timeout(void *);
 
 Static usbd_status	ehci_allocm(struct usbd_bus *, usb_dma_t *, u_int32_t);
 Static void		ehci_freem(struct usbd_bus *, usb_dma_t *);
@@ -489,6 +490,7 @@ ehci_init(ehci_softc_t *sc)
 	EOWRITE4(sc, EHCI_ASYNCLISTADDR, sqh->physaddr | EHCI_LINK_QH);
 
 	usb_callout_init(sc->sc_tmo_pcd);
+	usb_callout_init(sc->sc_tmo_intrlist);
 
 	lockinit(&sc->sc_doorbell_lock, PZERO, "ehcidb", 0, 0);
 
@@ -692,6 +694,12 @@ ehci_softintr(void *v)
 		ehci_check_intr(sc, ex);
 	}
 
+	/* Schedule a callout to catch any dropped transactions. */
+	if ((sc->sc_flags & EHCI_SCFLG_LOSTINTRBUG) &&
+	    !LIST_EMPTY(&sc->sc_intrhead))
+		usb_callout(sc->sc_tmo_intrlist, hz / 5, ehci_intrlist_timeout,
+		   sc);
+
 #ifdef USB_USE_SOFTINTR
 	if (sc->sc_softwake) {
 		sc->sc_softwake = 0;
@@ -942,6 +950,7 @@ ehci_detach(struct ehci_softc *sc, int flags)
 	EOWRITE4(sc, EHCI_USBINTR, sc->sc_eintrs);
 	EOWRITE4(sc, EHCI_USBCMD, 0);
 	EOWRITE4(sc, EHCI_USBCMD, EHCI_CMD_HCRESET);
+	usb_uncallout(sc->sc_tmo_intrlist, ehci_intrlist_timeout, sc);
 	usb_uncallout(sc->sc_tmo_pcd, ehci_pcd_enable, sc);
 
 #if defined(__NetBSD__) || defined(__OpenBSD__)
@@ -2700,6 +2709,29 @@ ehci_timeout_task(void *addr)
 	splx(s);
 }
 
+/*
+ * Some EHCI chips from VIA seem to trigger interrupts before writing back the
+ * qTD status, or miss signalling occasionally under heavy load.  If the host
+ * machine is too fast, we we can miss transaction completion - when we scan
+ * the active list the transaction still seems to be active.  This generally
+ * exhibits itself as a umass stall that never recovers.
+ *
+ * We work around this behaviour by setting up this callback after any softintr
+ * that completes with transactions still pending, giving us another chance to
+ * check for completion after the writeback has taken place.
+ */
+void
+ehci_intrlist_timeout(void *arg)
+{
+	ehci_softc_t *sc = arg;
+	int s = splusb();
+
+	DPRINTFN(3, ("ehci_intrlist_timeout\n"));
+	usb_schedsoftintr(&sc->sc_bus);
+
+	splx(s);
+}
+
 /************************/
 
 Static usbd_status
diff --git a/sys/dev/usb/ehci_pci.c b/sys/dev/usb/ehci_pci.c
index 9918efc..b03d94c 100644
--- a/sys/dev/usb/ehci_pci.c
+++ b/sys/dev/usb/ehci_pci.c
@@ -373,6 +373,10 @@ ehci_pci_attach(device_t self)
 		return ENXIO;
 	}
 
+	/* Enable workaround for dropped interrupts as required */
+	if (pci_get_vendor(self) == PCI_EHCI_VENDORID_VIA)
+		sc->sc_flags |= EHCI_SCFLG_LOSTINTRBUG;
+
 	/*
 	 * Find companion controllers.  According to the spec they always
 	 * have lower function numbers so they should be enumerated already.
diff --git a/sys/dev/usb/ehcivar.h b/sys/dev/usb/ehcivar.h
index f7a2029..e1b852d 100644
--- a/sys/dev/usb/ehcivar.h
+++ b/sys/dev/usb/ehcivar.h
@@ -94,6 +94,7 @@ struct ehci_soft_islot {
 #define EHCI_COMPANION_MAX 8
 
 #define EHCI_SCFLG_DONEINIT	0x0001	/* ehci_init() has been called. */
+#define EHCI_SCFLG_LOSTINTRBUG	0x0002	/* workaround for VIA chipsets */
 
 typedef struct ehci_softc {
 	struct usbd_bus sc_bus;		/* base device */
@@ -153,6 +154,7 @@ typedef struct ehci_softc {
 	struct lock sc_doorbell_lock;
 
 	usb_callout_t sc_tmo_pcd;
+	usb_callout_t sc_tmo_intrlist;
 
 #if defined(__NetBSD__) || defined(__OpenBSD__)
 	device_ptr_t sc_child;		/* /dev/usb# device */