Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751860AbdHCOsL (ORCPT ); Thu, 3 Aug 2017 10:48:11 -0400 Received: from foss.arm.com ([217.140.101.70]:41482 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751857AbdHCOsJ (ORCPT ); Thu, 3 Aug 2017 10:48:09 -0400 Subject: Re: [PATCH v2] dma-mapping: skip USB devices when configuring DMA during probe To: Johan Hovold , Alan Stern Cc: Christoph Hellwig , Marek Szyprowski , Greg Kroah-Hartman , =?UTF-8?Q?Andreas_F=c3=a4rber?= , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, stable , Sricharan R , Stefan Wahren References: <20170803131444.4101-1-johan@kernel.org> <20170803142308.GU30136@localhost> From: Robin Murphy Message-ID: Date: Thu, 3 Aug 2017 15:48:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170803142308.GU30136@localhost> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2681 Lines: 65 On 03/08/17 15:23, Johan Hovold wrote: > 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. :-/ Oh bum, I hadn't even realised usb_bus_type could be modular. > Add another flag (e.g. skip_dma_configure) to struct device for now? Would it be sufficient to look for dev->of_node_reused, or is it also possible for USB devices to have OF nodes of their own such that of_dma_configure() would still blat the mask with a 32-bit default? (Although that would still un-break Rpi3, even if strictly wrong) Robin.