From patchwork Tue Sep 13 08:16:03 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roger Quadros X-Patchwork-Id: 76041 Delivered-To: patch@linaro.org Received: by 10.140.106.72 with SMTP id d66csp1243564qgf; Tue, 13 Sep 2016 01:16:24 -0700 (PDT) X-Received: by 10.66.253.101 with SMTP id zz5mr41320120pac.32.1473754584731; Tue, 13 Sep 2016 01:16:24 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id pl6si19664326pab.281.2016.09.13.01.16.24; Tue, 13 Sep 2016 01:16:24 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756079AbcIMIQW (ORCPT + 27 others); Tue, 13 Sep 2016 04:16:22 -0400 Received: from arroyo.ext.ti.com ([198.47.19.12]:47565 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751967AbcIMIQT (ORCPT ); Tue, 13 Sep 2016 04:16:19 -0400 Received: from dflxv15.itg.ti.com ([128.247.5.124]) by arroyo.ext.ti.com (8.13.7/8.13.7) with ESMTP id u8D8G9Ip007018; Tue, 13 Sep 2016 03:16:09 -0500 Received: from DLEE70.ent.ti.com (dlee70.ent.ti.com [157.170.170.113]) by dflxv15.itg.ti.com (8.14.3/8.13.8) with ESMTP id u8D8G99i006163; Tue, 13 Sep 2016 03:16:09 -0500 Received: from dflp32.itg.ti.com (10.64.6.15) by DLEE70.ent.ti.com (157.170.170.113) with Microsoft SMTP Server id 14.3.294.0; Tue, 13 Sep 2016 03:16:06 -0500 Received: from [192.168.2.6] (ileax41-snat.itg.ti.com [10.172.224.153]) by dflp32.itg.ti.com (8.14.3/8.13.8) with ESMTP id u8D8G3KJ013687; Tue, 13 Sep 2016 03:16:03 -0500 Subject: [PATCH v4] usb: core: setup dma_pfn_offset for USB devices and, interfaces To: , References: <1471437328-8621-1-git-send-email-rogerq@ti.com> CC: , , , , Arnd Bergmann , From: Roger Quadros Message-ID: <92772fe0-5c3d-b2f0-6ab3-0504f29de7e4@ti.com> Date: Tue, 13 Sep 2016 11:16:03 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If dma_pfn_offset is not inherited correctly from the host controller, it might result in sub-optimal configuration as bounce buffer limit might be set to less than optimal level. Consider the mass storage device case. USB storage driver creates a scsi host for the mass storage interface in drivers/usb/storage/usb.c The scsi host parent device is nothing but the the USB interface device. Now, __scsi_init_queue() calls scsi_calculate_bounce_limit() to find out and set the block layer bounce limit. scsi_calculate_bounce_limit() uses dma_max_pfn(host_dev) to get the bounce_limit. host_dev is nothing but the device representing the mass storage interface. If that device doesn't have the right dma_pfn_offset, then dma_max_pfn() is messed up and the bounce buffer limit is wrong. e.g. On Keystone 2 systems, dma_max_pfn() is 0x87FFFF and dma_mask_pfn is 0xFFFFF. Consider a mass storage use case: Without this patch, usb scsi host device (usb-storage) will get a dma_pfn_offset of 0 resulting in a dma_max_pfn() of 0xFFFFF within the scsi layer (scsi_calculate_bounce_limit()). This will result in bounce buffers being unnecessarily used. Hint: On 32-bit ARM platforms dma_max_pfn() = dma_mask_pfn + dma_pfn_offset Signed-off-by: Roger Quadros --- Changelog: v4: - added comment in the code as to why we need to set dma_mask and dma_pfn_offset for usb devices. v3: - removed comments from code as commit log is sufficient. v2: - added more information in commit log and code. drivers/usb/core/message.c | 5 +++++ drivers/usb/core/usb.c | 11 +++++++++++ 2 files changed, 16 insertions(+) -- 2.7.4 Acked-by: Arnd Bergmann diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c index 0406a59..bb617df 100644 --- a/drivers/usb/core/message.c +++ b/drivers/usb/core/message.c @@ -1862,7 +1862,12 @@ free_interfaces: intf->dev.bus = &usb_bus_type; intf->dev.type = &usb_if_device_type; intf->dev.groups = usb_interface_groups; + /* + * Please refer to usb_alloc_dev() to see why we set + * dma_mask and dma_pfn_offset. + */ intf->dev.dma_mask = dev->dev.dma_mask; + intf->dev.dma_pfn_offset = dev->dev.dma_pfn_offset; INIT_WORK(&intf->reset_ws, __usb_queue_reset_device); intf->minor = -1; device_initialize(&intf->dev); diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index 5e80697..5921514 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -440,7 +440,18 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent, dev->dev.bus = &usb_bus_type; dev->dev.type = &usb_device_type; dev->dev.groups = usb_device_groups; + /* + * Fake a dma_mask/offset for the USB device: + * We cannot really use the dma-mapping API (dma_alloc_* and + * dma_map_*) for USB devices but instead need to use + * usb_alloc_coherent and pass data in 'urb's, but some subsystems + * manually look into the mask/offset pair to determine whether + * they need bounce buffers. + * Note: calling dma_set_mask() on a USB device would set the + * mask for the entire HCD, so don't do that. + */ dev->dev.dma_mask = bus->controller->dma_mask; + dev->dev.dma_pfn_offset = bus->controller->dma_pfn_offset; set_dev_node(&dev->dev, dev_to_node(bus->controller)); dev->state = USB_STATE_ATTACHED; dev->lpm_disable_count = 1;