From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA445C433E0 for ; Mon, 1 Mar 2021 16:00:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7701164D8F for ; Mon, 1 Mar 2021 16:00:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237470AbhCAQAK (ORCPT ); Mon, 1 Mar 2021 11:00:10 -0500 Received: from netrider.rowland.org ([192.131.102.5]:50797 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S237135AbhCAQAI (ORCPT ); Mon, 1 Mar 2021 11:00:08 -0500 Received: (qmail 1490911 invoked by uid 1000); 1 Mar 2021 10:59:27 -0500 Date: Mon, 1 Mar 2021 10:59:27 -0500 From: Alan Stern To: Christoph Hellwig , Hans de Goede Cc: Tom Yan , linux-usb , Linux Kernel Mailing List , SCSI development list Subject: Re: [PATCH 2/2] usb-storage: revert from scsi_add_host_with_dma() to scsi_add_host() Message-ID: <20210301155927.GB1490228@rowland.harvard.edu> References: <186eb035-4bc4-ff72-ee41-aeb6d81888e3@redhat.com> <20201130172004.GA966032@rowland.harvard.edu> <20201130203618.GB975529@rowland.harvard.edu> <20210225163557.GC1350993@rowland.harvard.edu> <20210226055352.GA2996@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210226055352.GA2996@lst.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Fri, Feb 26, 2021 at 06:53:52AM +0100, Christoph Hellwig wrote: > On Thu, Feb 25, 2021 at 11:35:57AM -0500, Alan Stern wrote: > > This thread seems to have fallen through the cracks. Maybe now would be > > a good time to address the problem (since we originally planned to fix > > it in 5.11!). > > > > The questions listed below are pretty self-contained, although the rest > > of the discussion isn't. But I never received any answers. > > usb-storage must use scsi_add_host_with_dma to use the right device > for DMA mapping and parameters. The calls to set the DMA options > on the device are needed so that IOMMU merging doesn't change the > imposed requirements. If these requirements slow you down you need > to relax them, as apparently the hardware is able to handle bigger > limits. Hans, don't you have the right equipment to test this approach? Alan Stern