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[209.85.128.46]) by smtp.gmail.com with ESMTPSA id sd17sm19031970ejb.93.2020.08.19.06.58.10 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2020 06:58:11 -0700 (PDT) Received: by mail-wm1-f46.google.com with SMTP id 3so2322486wmi.1 for ; Wed, 19 Aug 2020 06:58:10 -0700 (PDT) X-Received: by 2002:a1c:5581:: with SMTP id j123mr5137250wmb.11.1597845489930; Wed, 19 Aug 2020 06:58:09 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> In-Reply-To: <20200819135454.GA17098@lst.de> From: Tomasz Figa Date: Wed, 19 Aug 2020 15:57:53 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Christoph Hellwig Cc: Mauro Carvalho Chehab , Thomas Bogendoerfer , "James E.J. Bottomley" , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Ben Skeggs , Pawel Osciak , Marek Szyprowski , Matt Porter , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Tom Lendacky , alsa-devel@alsa-project.org, linux-samsung-soc , linux-ia64@vger.kernel.org, linux-scsi@vger.kernel.org, linux-parisc@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, Linux Kernel Mailing List , linux-nvme@lists.infradead.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Linux Media Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz 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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 1C332C433E1 for ; Wed, 19 Aug 2020 13:58:20 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D9E942076E for ; Wed, 19 Aug 2020 13:58:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="BXcvQo0I"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="m4IkKgPl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D9E942076E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:To:Subject:Message-ID:Date:From:In-Reply-To: References:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Q0cjIXGbK+73RLfyJAT3YYodboIdkh6kXKNhqiOMlQM=; b=BXcvQo0IuW4YOHmggZFtWssT3 pEn84GslbA9t7ItE3JP0uC7WrhMM/PBPHFHgplm/iPuJAae3FgFjXrcIR8xWRZMyinSFKS/7JBeTG 6PT+ZI5pSkwn4fqFawI+rbq4G0DpVIt4UNLUIH8Koennw+7j73KXs5PlLJRW6Qij7nBWVAwI71OVm +ZHn7tdLKbCB+B6Yk6QGhg9ALwOSf7M7p2dr0sdxwZu4bDhBYGA94JnHTxFAGi+jABxqcbjF0onz2 sR8rfoeSPYOnxe1O+sa/gaE1pK2MY9z2GhM9JCzDtg7oMzq2cxz12KtVddrS/bMUz6p21SO8nvRlB ogctRXTug==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k8ObY-0007ac-Qr; Wed, 19 Aug 2020 13:58:16 +0000 Received: from mail-ej1-x644.google.com ([2a00:1450:4864:20::644]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k8ObV-0007Yt-JW for linux-nvme@lists.infradead.org; Wed, 19 Aug 2020 13:58:14 +0000 Received: by mail-ej1-x644.google.com with SMTP id t10so26400437ejs.8 for ; Wed, 19 Aug 2020 06:58:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=m4IkKgPlDJh9Ow/m1Q5dtgZrYLnaRCS7od5vd7CevPl4aSkNJcXDYSbofI9IVrnSM1 T0Nk8lAEv28vGxYfqJpLVc+ygPg3eNS610ZSiKpYmXTIZXUzbw+fr6qoGPkql89ad0SH sz82upHUpsjkfyqDK6oYGAHuFg3NLWv3KpWnw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=fKYyuhpfPvHQa3MFEANViOn96meEwj6gYme4/j7kj783JmJINHOtmnjb3OOIa1HvQX Ch1tJZalA1l6yuiE1YjitvyScKQhl2AZdCJn3s4s7XkfEl0xdMfhs595M8hJNr0i/IKW jAiw5ILni4U4N7ohLxelGTGUpIR9mJoBH/VarwwO5sP00kKQhJMsdl/PQdw6jo8q4vpo zrJRnsFAv4ZWwia/LJIWH42YYlQNSO2Yi5ltywY/nqfCLZ9OI+fKTtcSBczykIHD4CYb gv6zBXGbviSgYHYQ5T96dSBkoICPkgOoyDXrCFNuPCSAdPD/LcdYjXzkZUcRHEHw9Ver J2Vw== X-Gm-Message-State: AOAM5315wu0e9NgSU0JMaFJX9OrpFdlM7dBiVp74W2y9OP3rFN1labIw BDEjCxBSFPgOoODONPSeKrGo4nz2vtRJsA== X-Google-Smtp-Source: ABdhPJy/cfJel72sPCEsw4RFz4EHVpYoYc3w95wnVDKRDhQou7PFalRdyzFX3AHuhB39/73MJowckA== X-Received: by 2002:a17:906:c187:: with SMTP id g7mr4516153ejz.108.1597845492045; Wed, 19 Aug 2020 06:58:12 -0700 (PDT) Received: from mail-wm1-f43.google.com (mail-wm1-f43.google.com. [209.85.128.43]) by smtp.gmail.com with ESMTPSA id cn27sm18274093edb.4.2020.08.19.06.58.11 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2020 06:58:11 -0700 (PDT) Received: by mail-wm1-f43.google.com with SMTP id f18so1734306wmc.0 for ; Wed, 19 Aug 2020 06:58:11 -0700 (PDT) X-Received: by 2002:a1c:5581:: with SMTP id j123mr5137250wmb.11.1597845489930; Wed, 19 Aug 2020 06:58:09 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> In-Reply-To: <20200819135454.GA17098@lst.de> From: Tomasz Figa Date: Wed, 19 Aug 2020 15:57:53 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Christoph Hellwig X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200819_095813_882180_5CDB39CE X-CRM114-Status: GOOD ( 19.57 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, Linux Kernel Mailing List , "James E.J. Bottomley" , linux-mm@kvack.org, Marek Szyprowski , linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, Kyungmin Park , Ben Skeggs , Matt Porter , Linux Media Mailing List , Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel , " Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme 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=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 A96B9C433DF for ; Wed, 19 Aug 2020 14:17:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 535C920639 for ; Wed, 19 Aug 2020 14:17:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="m4IkKgPl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 535C920639 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EE1B96B00B2; Wed, 19 Aug 2020 10:17:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E90D38D0041; Wed, 19 Aug 2020 10:17:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D596E6B00B4; Wed, 19 Aug 2020 10:17:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0045.hostedemail.com [216.40.44.45]) by kanga.kvack.org (Postfix) with ESMTP id B7E666B00B2 for ; Wed, 19 Aug 2020 10:17:52 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 64E743637 for ; Wed, 19 Aug 2020 14:17:52 +0000 (UTC) X-FDA: 77167521984.18.stone19_1b1659327028 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id DC30B100ED9DE for ; Wed, 19 Aug 2020 14:17:50 +0000 (UTC) X-HE-Tag: stone19_1b1659327028 X-Filterd-Recvd-Size: 5442 Received: from mail-wr1-f67.google.com (mail-wr1-f67.google.com [209.85.221.67]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Wed, 19 Aug 2020 14:17:50 +0000 (UTC) Received: by mail-wr1-f67.google.com with SMTP id a5so21722648wrm.6 for ; Wed, 19 Aug 2020 07:17:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=m4IkKgPlDJh9Ow/m1Q5dtgZrYLnaRCS7od5vd7CevPl4aSkNJcXDYSbofI9IVrnSM1 T0Nk8lAEv28vGxYfqJpLVc+ygPg3eNS610ZSiKpYmXTIZXUzbw+fr6qoGPkql89ad0SH sz82upHUpsjkfyqDK6oYGAHuFg3NLWv3KpWnw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=ZVKx597eOWxGVo0U0NIJWbtaOOwJizUtdgRwA5mqH0MdXBmXF7wSubGim+BJj5Gm4T XAvXzLDefeARoLWJggJosXfwQxseDMHWZQsrDLl9E1p9jYWLqe49MJ+LKofOTwrUCoTY 5nuZTZtnB34dVtdG2p/WXQZfCgpuaCaFizDnTmTDhsBP9omrSN7AMs+FqpoKrSUz3X+I Ex9m77zjz73x8iz69mDQwjp5byZ3e6/9maI23M2Exv9FepRP73qJDDo/zx9XOEvKbpIF KjZTwC+CJZ9dFOQR/93AXGgqiNhhc3N3ekEonwmrbJQjWOwOc7yiqnpzzU3iBaWTv2xL PyvQ== X-Gm-Message-State: AOAM532SsvBqRPGdmVwQ+5t476h92TmHLlWTxipMAO8fVB2boidPOtJU 60uO8BKyIfsTZU0GzIatchFLaTfKNz5X1g== X-Google-Smtp-Source: ABdhPJyrHYwSOKwmdmCnDzIJvLBo6CSKIhb4a5fNoW1kiFs9fEdjkt7DOvANjLxilT7ryz9/4+or9w== X-Received: by 2002:a17:906:289a:: with SMTP id o26mr24913628ejd.309.1597845948567; Wed, 19 Aug 2020 07:05:48 -0700 (PDT) Received: from mail-wm1-f47.google.com (mail-wm1-f47.google.com. [209.85.128.47]) by smtp.gmail.com with ESMTPSA id gh25sm18488363ejb.109.2020.08.19.07.05.48 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2020 07:05:48 -0700 (PDT) Received: by mail-wm1-f47.google.com with SMTP id k8so2346224wma.2 for ; Wed, 19 Aug 2020 07:05:48 -0700 (PDT) X-Received: by 2002:a1c:5581:: with SMTP id j123mr5137250wmb.11.1597845489930; Wed, 19 Aug 2020 06:58:09 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> In-Reply-To: <20200819135454.GA17098@lst.de> From: Tomasz Figa Date: Wed, 19 Aug 2020 15:57:53 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Christoph Hellwig Cc: Mauro Carvalho Chehab , Thomas Bogendoerfer , "James E.J. Bottomley" , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Ben Skeggs , Pawel Osciak , Marek Szyprowski , Matt Porter , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Tom Lendacky , alsa-devel@alsa-project.org, linux-samsung-soc , linux-ia64@vger.kernel.org, linux-scsi@vger.kernel.org, linux-parisc@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, Linux Kernel Mailing List , linux-nvme@lists.infradead.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Linux Media Mailing List Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: DC30B100ED9DE X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz 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=-3.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 D2C88C433E1 for ; Fri, 21 Aug 2020 07:51:13 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5BC8820738 for ; Fri, 21 Aug 2020 07:51:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="DDvF0oww"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="m4IkKgPl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5BC8820738 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id DEC0C1669; Fri, 21 Aug 2020 09:50:21 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz DEC0C1669 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1597996271; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=DDvF0owwp/6KofDVydAAzc6NhczsURkCFHX8bBsGFEy+O0f3O3/MHmrHFl6k1R9Bl eGUb0qVZ+Qi7mRqM2yern1yXZZhCaN+viBOXxVkUnbggAqKMKKAA/yPOO4jMXLf/3m pVh3FnnRZ4yadgw0/y3TX70ff241t7AaoFO6+FfM= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id E1E4CF802FF; Fri, 21 Aug 2020 09:36:24 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id A2056F80218; Wed, 19 Aug 2020 15:58:25 +0200 (CEST) Received: from mail-ej1-x644.google.com (mail-ej1-x644.google.com [IPv6:2a00:1450:4864:20::644]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 8F0B1F8011C for ; Wed, 19 Aug 2020 15:58:15 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 8F0B1F8011C Authentication-Results: alsa1.perex.cz; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="m4IkKgPl" Received: by mail-ej1-x644.google.com with SMTP id bo3so26366026ejb.11 for ; Wed, 19 Aug 2020 06:58:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=m4IkKgPlDJh9Ow/m1Q5dtgZrYLnaRCS7od5vd7CevPl4aSkNJcXDYSbofI9IVrnSM1 T0Nk8lAEv28vGxYfqJpLVc+ygPg3eNS610ZSiKpYmXTIZXUzbw+fr6qoGPkql89ad0SH sz82upHUpsjkfyqDK6oYGAHuFg3NLWv3KpWnw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=UDBUB7gsVCesJZGKq5p3GRhlZnEY5Y8m+0lIfPiJ56ThAKqnYHE1u6UN99t2TLq6wL UawVITSByidUN1vRFpm240Z15xuO+66MHn6Uc7//PeIlbnIuiBsxcQ6UkPg7E9mG+z6U L+jP5HMReO5pR2X7xaQDWZC18iawmq7LJzBOxlT4lzmjoVHdCsTvJG3WJWmH+oO3bd+n AtWNlLh3E6sGXBW0eOMTsEGF6nnXygCSGu3dXcJWWh+1/f+I3t5vq5ngPwN0G7cel6y6 6qG9TLB2C4sd1unnisJ7BbjVTW/PdTm+ybmbveuCtESaaWufebSLyua1aBPlWvo8x63a E3nQ== X-Gm-Message-State: AOAM531oO1XZ7Op4LZhUbXsLcO93sAzE+CutWM+AXZccPNFpM4kA8vMj PwN6RoS1VtOAQ8EToPpfNoBW1CEoq1pWQA== X-Google-Smtp-Source: ABdhPJzga+Y5Qg9pjgqElygD3DVyX0ThVJER49iWw2tIkgm5edkGTWFxmfbZtyC7MuY5gaQfUP3ouw== X-Received: by 2002:a17:906:1c84:: with SMTP id g4mr26361688ejh.50.1597845494038; Wed, 19 Aug 2020 06:58:14 -0700 (PDT) Received: from mail-wm1-f46.google.com (mail-wm1-f46.google.com. [209.85.128.46]) by smtp.gmail.com with ESMTPSA id cn27sm18274060edb.4.2020.08.19.06.58.10 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2020 06:58:11 -0700 (PDT) Received: by mail-wm1-f46.google.com with SMTP id k20so2301040wmi.5 for ; Wed, 19 Aug 2020 06:58:10 -0700 (PDT) X-Received: by 2002:a1c:5581:: with SMTP id j123mr5137250wmb.11.1597845489930; Wed, 19 Aug 2020 06:58:09 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> In-Reply-To: <20200819135454.GA17098@lst.de> From: Tomasz Figa Date: Wed, 19 Aug 2020 15:57:53 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Christoph Hellwig Content-Type: text/plain; charset="UTF-8" X-Mailman-Approved-At: Fri, 21 Aug 2020 09:36:14 +0200 Cc: alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, Linux Kernel Mailing List , "James E.J. Bottomley" , linux-mm@kvack.org, Marek Szyprowski , linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, Kyungmin Park , Ben Skeggs , Matt Porter , Linux Media Mailing List , Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel , " X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Figa Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT Date: Wed, 19 Aug 2020 15:57:53 +0200 Message-ID: References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20200819135454.GA17098@lst.de> Sender: linux-scsi-owner@vger.kernel.org To: Christoph Hellwig Cc: Mauro Carvalho Chehab , Thomas Bogendoerfer , "James E.J. Bottomley" , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Ben Skeggs , Pawel Osciak , Marek Szyprowski , Matt Porter , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Tom Lendacky , alsa-devel@alsa-project.org, linux-samsung-soc , linux-ia64@vger.kernel.org, linux-scsi@vger.kernel.org, linux-parisc@vger.k List-Id: nouveau.vger.kernel.org On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz 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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 D0E44C433E1 for ; Wed, 19 Aug 2020 14:04:03 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 98981204FD for ; Wed, 19 Aug 2020 14:04:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="m4IkKgPl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 98981204FD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 6315B86BB4; Wed, 19 Aug 2020 14:04:03 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZXpwJQNVeHqH; Wed, 19 Aug 2020 14:04:02 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id D400586B6F; Wed, 19 Aug 2020 14:04:02 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id C6642C0889; Wed, 19 Aug 2020 14:04:02 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5A439C0051 for ; Wed, 19 Aug 2020 14:04:01 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 4127D20017 for ; Wed, 19 Aug 2020 14:04:01 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id k7vCQZB1PYk6 for ; Wed, 19 Aug 2020 14:04:00 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-ej1-f66.google.com (mail-ej1-f66.google.com [209.85.218.66]) by silver.osuosl.org (Postfix) with ESMTPS id BBF672000B for ; Wed, 19 Aug 2020 14:03:59 +0000 (UTC) Received: by mail-ej1-f66.google.com with SMTP id o23so26471999ejr.1 for ; Wed, 19 Aug 2020 07:03:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=m4IkKgPlDJh9Ow/m1Q5dtgZrYLnaRCS7od5vd7CevPl4aSkNJcXDYSbofI9IVrnSM1 T0Nk8lAEv28vGxYfqJpLVc+ygPg3eNS610ZSiKpYmXTIZXUzbw+fr6qoGPkql89ad0SH sz82upHUpsjkfyqDK6oYGAHuFg3NLWv3KpWnw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=hHWtIh2yIBKBJKZpgI8qIk2WrqUOVNLX/HiYDITyynnSv8BkdXhF9hKmGPYcoIiP6t 0sFcb4nHYj0A6k2L5+Q9CrjwYQa5oeznlAS2kS8fX40F5d2Hw5t2gN2progYs7A3UJrZ kLpAujy3p4IEU26Ac+n089w66liOs0UPPBYrk1Jmw5vRfQeu8qum9waGLvwU/8b+zvvI PfwWRAKfCnUa3MILT/mgRQuPQ3MXAe+0muLXksVM8sweFQuo9c6us7L3aCsXLIvQMnD3 An1M1LFCQxeND57V8C6tXTt6deFexAgQKny/RsYfnUEJ+QhCUvjWbZr+VKQpcj/SDl4x jVDw== X-Gm-Message-State: AOAM531XmYsNScv44nNXWZTTM4/PAupboZxoGbGQTu3+LCqJ1lUer7bT AqA6Iw3sjag6IxMYzrzTwhAc8COjFKI05g== X-Google-Smtp-Source: ABdhPJxW8/m7OVbbiEExaM3NOpOLHGOiwsdql4iBqAvXr60mQEKepLWcxs4/lAvDoANFibTWlL+rKg== X-Received: by 2002:a17:906:5f8f:: with SMTP id a15mr26728880eju.291.1597845837973; Wed, 19 Aug 2020 07:03:57 -0700 (PDT) Received: from mail-wm1-f54.google.com (mail-wm1-f54.google.com. [209.85.128.54]) by smtp.gmail.com with ESMTPSA id u24sm17789640edq.23.2020.08.19.07.03.57 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2020 07:03:57 -0700 (PDT) Received: by mail-wm1-f54.google.com with SMTP id t14so2334028wmi.3 for ; Wed, 19 Aug 2020 07:03:57 -0700 (PDT) X-Received: by 2002:a1c:5581:: with SMTP id j123mr5137250wmb.11.1597845489930; Wed, 19 Aug 2020 06:58:09 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> In-Reply-To: <20200819135454.GA17098@lst.de> From: Tomasz Figa Date: Wed, 19 Aug 2020 15:57:53 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Christoph Hellwig Cc: alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, Linux Kernel Mailing List , "James E.J. Bottomley" , linux-mm@kvack.org, linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, Kyungmin Park , Ben Skeggs , Matt Porter , Linux Media Mailing List , Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel , " X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 56CE8C433E1 for ; Wed, 19 Aug 2020 14:07:03 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2087C204FD for ; Wed, 19 Aug 2020 14:07:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="oSnK9syk"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="m4IkKgPl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2087C204FD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:To:Subject:Message-ID:Date:From:In-Reply-To: References:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=uk9TA1AuD2Icj0lie0Wwdwnzw9pBsmEl/xPm24G7tno=; b=oSnK9sykaFM2endbcsU4qT3n3 B3BcVJGtpA5Ak/GJvdP2xMzYyglfZRbpw2mlyH4p9H3+AVmxjEz2EbDXJVb2Fybw+sxpw7WSkFF5w zqCSE3zNUkl+ppifvkrASIKk0MNuSqJqcL5atft9b5NnFJ5a4dR9qhMz3YL1/l3hNo9+m987AtbJF UFvcpJ7g0+dFmdWg1DsfBA8orn1YhadytWAOHwDg3F4GD3CHZB9nh5pIzvpEgKaXp+LufOpQMSVJC 4MgQwFTNjDtc0iVS/6QQnUxgSgzu2QP7z+JrWUaw3uvFghFtviZVsogqAdoN4Bc7ZGu/VtHaNMm9c AqryMqvcQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k8Oif-00016w-4z; Wed, 19 Aug 2020 14:05:37 +0000 Received: from mail-ej1-x644.google.com ([2a00:1450:4864:20::644]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k8Oib-000162-ST for linux-arm-kernel@lists.infradead.org; Wed, 19 Aug 2020 14:05:34 +0000 Received: by mail-ej1-x644.google.com with SMTP id o23so26478669ejr.1 for ; Wed, 19 Aug 2020 07:05:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=m4IkKgPlDJh9Ow/m1Q5dtgZrYLnaRCS7od5vd7CevPl4aSkNJcXDYSbofI9IVrnSM1 T0Nk8lAEv28vGxYfqJpLVc+ygPg3eNS610ZSiKpYmXTIZXUzbw+fr6qoGPkql89ad0SH sz82upHUpsjkfyqDK6oYGAHuFg3NLWv3KpWnw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6xkguvOzsgzZf/2nZcmiUdLktaalZbMKG8kwCTKJnbQ=; b=f9LZ66f86k9929uNGBu6c6GrzngheH4vKX8mZGoBu071A/D6HlckLz2fLQYCvYyjT1 nN5fjv50tXNjiSh98HhjgycA1qiUtP7E6USQM+oC7oJmu/N45gd9VI1js12ahCAzALcm MBhdoxPRlUgxlMgqIf3fStDtzT61xv0p/J7KYaa1omaMfLTmbW9mazrKtqmuFJ0FK/jd +Nkk/zm19jHoToze+cTH6X1c8q3h7IQK0jEx3B7RrhobTLRiAX5gwRuRPqER1wikWEk6 OItTRK1aNkaRa0mxReyvRcEFiHQpuxXlTg4z6XDf70o9Ai5ZLb+8pvY4NSgx+bqk7Xki XokA== X-Gm-Message-State: AOAM532QhAizAI5d4oV+3/ecDM33hj56Tq5MeyxgRi92Gm8U3L7BSKfu 9kkVVnSLh1VpnopDhm0o4lX9SI7yCshAdA== X-Google-Smtp-Source: ABdhPJznMCAu9iiMzUu+5op78pMcUdeMXCb+sNqj88HNIlPpUQQ+qe9ND3bf+46zfGJ1CGmvbSUTZw== X-Received: by 2002:a17:907:11dd:: with SMTP id va29mr26210190ejb.470.1597845932338; Wed, 19 Aug 2020 07:05:32 -0700 (PDT) Received: from mail-wm1-f46.google.com (mail-wm1-f46.google.com. [209.85.128.46]) by smtp.gmail.com with ESMTPSA id c5sm18784119ejb.103.2020.08.19.07.05.31 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2020 07:05:32 -0700 (PDT) Received: by mail-wm1-f46.google.com with SMTP id c80so2229497wme.0 for ; Wed, 19 Aug 2020 07:05:31 -0700 (PDT) X-Received: by 2002:a1c:5581:: with SMTP id j123mr5137250wmb.11.1597845489930; Wed, 19 Aug 2020 06:58:09 -0700 (PDT) MIME-Version: 1.0 References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> In-Reply-To: <20200819135454.GA17098@lst.de> From: Tomasz Figa Date: Wed, 19 Aug 2020 15:57:53 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT To: Christoph Hellwig X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200819_100533_949265_12D046BD X-CRM114-Status: GOOD ( 19.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, Linux Kernel Mailing List , "James E.J. Bottomley" , linux-mm@kvack.org, Marek Szyprowski , linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, Kyungmin Park , Ben Skeggs , Matt Porter , Linux Media Mailing List , Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel , " Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Figa Date: Wed, 19 Aug 2020 13:57:53 +0000 Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT Message-Id: List-Id: References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> In-Reply-To: <20200819135454.GA17098@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Hellwig Cc: Mauro Carvalho Chehab , Thomas Bogendoerfer , "James E.J. Bottomley" , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Ben Skeggs , Pawel Osciak , Marek Szyprowski , Matt Porter , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Tom Lendacky , alsa-devel@alsa-project.org, linux-samsung-soc , linux-ia64@vger.kernel.org, linux-scsi@vger.kernel.org, linux-parisc@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, Linux Kernel Mailing List , linux-nvme@lists.infradead.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Linux Media Mailing List On Wed, Aug 19, 2020 at 3:55 PM Christoph Hellwig wrote: > > On Wed, Aug 19, 2020 at 01:16:51PM +0200, Tomasz Figa wrote: > > Hi Christoph, > > > > On Wed, Aug 19, 2020 at 8:56 AM Christoph Hellwig wrote: > > > > > > The V4L2-FLAG-MEMORY-NON-CONSISTENT flag is entirely unused, > > > > Could you explain what makes you think it's unused? It's a feature of > > the UAPI generally supported by the videobuf2 framework and relied on > > by Chromium OS to get any kind of reasonable performance when > > accessing V4L2 buffers in the userspace. > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > so by definition it isn't used by any of these media drivers. It's still an UAPI feature, so we can't simply remove the flag, it must stay there as a no-op, until the problem is resolved. Also, it of course might be disputable as an out-of-tree usage, but selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do something on other platforms, including ARM64. Best regards, Tomasz