Use the limited scatter-gather capabilities of ehci, ohci and uhci

host controllers to avoid the need to allocate any multi-page
physically contiguous memory blocks. This makes it possible to use
USB devices reliably on low-memory systems or when memory is too
fragmented for contiguous allocations to succeed.

The USB subsystem now uses bus_dmamap_load() directly on the buffers
supplied by USB peripheral drivers, so this also avoids having to
copy data back and forth before and after transfers. The ehci and
ohci controllers support scatter/gather as long as the buffer is
contiguous in the virtual address space. For uhci the hardware
cannot handle a physical address discontinuity within a USB packet,
so it is necessary to copy small memory fragments at times.

1 files changed, 30 insertions, 0 deletions

diff --git a/sys/dev/usb/ehci_pci.c b/sys/dev/usb/ehci_pci.c
index 204fad0..6ed26140 100644
--- a/sys/dev/usb/ehci_pci.c
+++ b/sys/dev/usb/ehci_pci.c
@@ -58,6 +58,8 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/kernel.h>
 #include <sys/module.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
 #include <sys/bus.h>
 #include <sys/queue.h>
 #include <sys/lockmgr.h>
@@ -420,6 +422,30 @@ ehci_pci_attach(device_t self)
 	}
 	sc->sc_ncomp = ncomp;
 
+	/* Allocate a parent dma tag for DMA maps */
+	err = bus_dma_tag_create(NULL, 1, 0, BUS_SPACE_MAXADDR_32BIT,
+	    BUS_SPACE_MAXADDR, NULL, NULL, BUS_SPACE_MAXSIZE_32BIT,
+	    USB_DMA_NSEG, BUS_SPACE_MAXSIZE_32BIT, 0, NULL, NULL,
+	    &sc->sc_bus.parent_dmatag);
+	if (err) {
+		device_printf(self, "Could not allocate parent DMA tag (%d)\n",
+		    err);
+		ehci_pci_detach(self);
+		return ENXIO;
+	}
+
+	/* Allocate a dma tag for transfer buffers */
+	err = bus_dma_tag_create(sc->sc_bus.parent_dmatag, 1, 0,
+	    BUS_SPACE_MAXADDR_32BIT, BUS_SPACE_MAXADDR, NULL, NULL,
+	    BUS_SPACE_MAXSIZE_32BIT, USB_DMA_NSEG, BUS_SPACE_MAXSIZE_32BIT, 0,
+	    busdma_lock_mutex, &Giant, &sc->sc_bus.buffer_dmatag);
+	if (err) {
+		device_printf(self, "Could not allocate buffer DMA tag (%d)\n",
+		    err);
+		ehci_pci_detach(self);
+		return ENXIO;
+	}
+
 	ehci_pci_takecontroller(self);
 	err = ehci_init(sc);
 	if (!err) {
@@ -450,6 +476,10 @@ ehci_pci_detach(device_t self)
 	 */
 	if (sc->iot && sc->ioh)
 		bus_space_write_4(sc->iot, sc->ioh, EHCI_USBINTR, 0);
+	if (sc->sc_bus.parent_dmatag != NULL)
+		bus_dma_tag_destroy(sc->sc_bus.parent_dmatag);
+	if (sc->sc_bus.buffer_dmatag != NULL)
+		bus_dma_tag_destroy(sc->sc_bus.buffer_dmatag);
 
 	if (sc->irq_res && sc->ih) {
 		int err = bus_teardown_intr(self, sc->irq_res, sc->ih);