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, 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 D78F5C4708F for ; Fri, 4 Jun 2021 09:02:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C183E613E4 for ; Fri, 4 Jun 2021 09:02:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230025AbhFDJEU (ORCPT ); Fri, 4 Jun 2021 05:04:20 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:38137 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229959AbhFDJET (ORCPT ); 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Fri, 4 Jun 2021 10:02:29 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.018; Fri, 4 Jun 2021 10:02:29 +0100 From: David Laight To: 'Palmer Dabbelt' , Anup Patel CC: "guoren@kernel.org" , "anup@brainfault.org" , "drew@beagleboard.org" , Christoph Hellwig , "wefu@redhat.com" , "lazyparser@gmail.com" , "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linux-sunxi@lists.linux.dev" , "guoren@linux.alibaba.com" , Paul Walmsley Subject: RE: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support Thread-Topic: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support Thread-Index: AQHXWI67+E+HbgFRkkm3Xv2DTkp7y6sDjh4w Date: Fri, 4 Jun 2021 09:02:29 +0000 Message-ID: References: In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210604_020237_942609_DA8840FC X-CRM114-Status: GOOD ( 12.07 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Palmer Dabbelt > Sent: 03 June 2021 16:39 ... > An example here would be the errata: every system has errata of some > sort, so if we start flipping off various vendor's errata Kconfigs > you'll end up with kernels that only function properly on some systems. > That's fine with me, as long as it's possible to turn on all vendor's > errata Kconfigs at the same time and the resulting kernel functions > correctly on all systems. ISTM that if you can (easily) detect the errata then the detection should be left it - but the kernel fail to boot if the system needs the errata fixed. The same would be needed for DMA in systems with non-coherent memory. Only a hardware engineer would build a system with non-coherent memory and without the ability to do uncached accesses and flush/invalidate small sections of cache. Mind you we did get a dual-cpu system that didn't have cache-coherency between the cpus! That was singularly useless. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv