Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751930AbdHCOXO (ORCPT ); Thu, 3 Aug 2017 10:23:14 -0400 Received: from mail-lf0-f68.google.com ([209.85.215.68]:35419 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751878AbdHCOXM (ORCPT ); Thu, 3 Aug 2017 10:23:12 -0400 Date: Thu, 3 Aug 2017 16:23:08 +0200 From: Johan Hovold To: Alan Stern Cc: Johan Hovold , Christoph Hellwig , Marek Szyprowski , Greg Kroah-Hartman , Andreas =?iso-8859-1?Q?F=E4rber?= , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, stable , Robin Murphy , Sricharan R , Stefan Wahren Subject: Re: [PATCH v2] dma-mapping: skip USB devices when configuring DMA during probe Message-ID: <20170803142308.GU30136@localhost> References: <20170803131444.4101-1-johan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2309 Lines: 58 On Thu, Aug 03, 2017 at 10:04:21AM -0400, Alan Stern wrote: > 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 > > --- > > 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? Nope. :-/ Add another flag (e.g. skip_dma_configure) to struct device for now? Thanks, Johan