Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752093AbdHCOEX (ORCPT ); Thu, 3 Aug 2017 10:04:23 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:41682 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751791AbdHCOEW (ORCPT ); Thu, 3 Aug 2017 10:04:22 -0400 Date: Thu, 3 Aug 2017 10:04:21 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Johan Hovold cc: Christoph Hellwig , Marek Szyprowski , Greg Kroah-Hartman , =?UTF-8?q?Andreas=20F=C3=A4rber?= , , , , stable , Robin Murphy , Sricharan R , Stefan Wahren Subject: Re: [PATCH v2] dma-mapping: skip USB devices when configuring DMA during probe In-Reply-To: <20170803131444.4101-1-johan@kernel.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2257 Lines: 58 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 # 4.12 > Cc: Robin Murphy > Cc: Sricharan R > Cc: Stefan Wahren > Reported-by: Hans Verkuil > Signed-off-by: Johan Hovold > --- > > 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