On Thu, 3 Aug 2017, Johan Hovold wrote: > USB devices use the DMA mask and offset of the controller, which have > already been setup when a device is probed. Note that modifying the > DMA mask of a USB device would change the mask for the controller (and > all devices on the bus) as the mask is literally shared. > > Since commit 2bf698671205 ("USB: of: fix root-hub device-tree node > handling"), of_dma_configure() would be called also for root hubs, which > use the device node of the controller. A separate, long-standing bug > that makes of_dma_configure() generate a 30-bit DMA mask from the RPI3's > "dma-ranges" would thus set a broken mask also for the controller. This > in turn prevents USB devices from enumerating when control transfers > fail: > > dwc2 3f980000.usb: Cannot do DMA to address 0x000000003a166a00 > > Note that the aforementioned DMA-mask bug was benign for the HCD itself > as the dwc2 driver overwrites the mask previously set by > of_dma_configure() for the platform device in its probe callback. The > mask would only later get corrupted when the root-hub child device was > probed. > > Fix this, and similar future problems, by simply skipping USB devices > when dma_configure() is called during probe. > > Fixes: 09515ef5ddad ("of/acpi: Configure dma operations at probe time for platform/amba/pci bus devices") > Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.12 > Cc: Robin Murphy <robin.murphy@xxxxxxx> > Cc: Sricharan R <sricharan@xxxxxxxxxxxxxx> > Cc: Stefan Wahren <stefan.wahren@xxxxxxxx> > Reported-by: Hans Verkuil <hverkuil@xxxxxxxxx> > Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> > --- > > v2 > - amend commit message and point out that the long-standing 30-bit DMA-mask > bug was benign to the dwc2 HCD itself (Robin) > - add and use a new dev_is_usb() helper (Robin) > diff --git a/include/linux/usb.h b/include/linux/usb.h > index cb9fbd54386e..f86ad9d8c756 100644 > --- a/include/linux/usb.h > +++ b/include/linux/usb.h > @@ -1222,6 +1222,11 @@ struct usb_device_driver { > > extern struct bus_type usb_bus_type; > > +static inline bool dev_is_usb(struct device *dev) > +{ > + return dev->bus == &usb_bus_type; > +} > + Will this work if the USB subsystem is built as a module? Alan Stern