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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 CE10FC282C4 for ; Tue, 12 Feb 2019 14:54:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6ACC2084E for ; Tue, 12 Feb 2019 14:54:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730538AbfBLOy2 (ORCPT ); Tue, 12 Feb 2019 09:54:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42178 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727562AbfBLOy1 (ORCPT ); Tue, 12 Feb 2019 09:54:27 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AAFA07F6C7; Tue, 12 Feb 2019 14:54:26 +0000 (UTC) Received: from localhost (ovpn-204-125.brq.redhat.com [10.40.204.125]) by smtp.corp.redhat.com (Postfix) with ESMTP id 40B2860C1C; Tue, 12 Feb 2019 14:54:26 +0000 (UTC) Date: Tue, 12 Feb 2019 15:54:25 +0100 From: Stanislaw Gruszka To: Lorenzo Bianconi Cc: Felix Fietkau , linux-wireless , lorenzo@kernel.org Subject: Re: [PATCH 0/4] do not use sg if not properly supported by usb controller Message-ID: <20190212145424.GE12906@redhat.com> References: <20190212134550.GA12256@redhat.com> <20190212135100.GA15292@redhat.com> <20190212141725.GD12906@redhat.com> <20190212142528.GB24197@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190212142528.GB24197@localhost.localdomain> User-Agent: Mutt/1.8.3 (2017-05-23) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Tue, 12 Feb 2019 14:54:26 +0000 (UTC) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Tue, Feb 12, 2019 at 03:25:30PM +0100, Lorenzo Bianconi wrote: > > On Tue, Feb 12, 2019 at 03:09:53PM +0100, Lorenzo Bianconi wrote: > > > > > > > > (repost with corrected Lorenzo email) > > > > > > > > On Tue, Feb 12, 2019 at 02:45:50PM +0100, Stanislaw Gruszka wrote: > > > > > On Tue, Feb 12, 2019 at 02:24:47PM +0100, LorenzoBianconilorenzo@kernel.org wrote: > > > > > > From: Lorenzo Bianconi > > > > > > > > > > > > Use linear fragment and not a single usb scatter-gather buffer in mt76u > > > > > > {tx,rx} datapath if the usb controller has sg data length constraints. > > > > > > Moreover add disable_usb_sg module parameter in order to explicitly > > > > > > disable scatter-gather. SG I/O is not supported by all host drivers and > > > > > > some users have reported sg issues on AMD IOMMU. > > > > > > > > > > Again. This is not right approach. SG issues should be fixed > > > > > not workarounded. > > > > > > Hi Stanislaw, > > > > > > here we do not use SG, so num_sg is 0 and we use transfer_buffer. I do > > > not see how I am working around the issue. > > > > By avoiding SG buffer allocation and configuration which most likely > > need to be fixed. > > In my series I: > 1- set num_sg to 0 > 2- use transfer_buffer > > please correct me if I am wrong but in your solution you did the same since AFAIK > PageHighMem is always 0 so you end up setting num_sg to 0 and using > transfer_buffer as well. Is my understanding correct? Yes. But it still using all existing SG allocation and setup code and buffer is tracked in urb->sg[0]. > > > Moreover with this approach we avoid some unnecessary operation in the hotpath > > > > What unnecessary operation ? > > the ones in mt76u_fill_bulk_urb() Your patches also add extra operations on hotpath due to urb->num_sgs and dev->usb.sg_en checks. Stanislaw