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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 D36BDC4646B for ; Wed, 26 Jun 2019 06:51:08 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 5D8BD2146E for ; Wed, 26 Jun 2019 06:51:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D8BD2146E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45YYZv38mGzDqJN for ; Wed, 26 Jun 2019 16:51:03 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=lst.de (client-ip=213.95.11.211; helo=newverein.lst.de; envelope-from=hch@lst.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=lst.de Received: from newverein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 45YYXm3MZyzDqFK for ; Wed, 26 Jun 2019 16:49:11 +1000 (AEST) Received: by newverein.lst.de (Postfix, from userid 2407) id 0462268B05; Wed, 26 Jun 2019 08:48:38 +0200 (CEST) Date: Wed, 26 Jun 2019 08:48:37 +0200 From: Christoph Hellwig To: Mark Greer Subject: Re: DMA coherency in drivers/tty/serial/mpsc.c Message-ID: <20190626064837.GA24531@lst.de> References: <20190625122641.GA4421@lst.de> <20190625163722.GA18626@animalcreek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190625163722.GA18626@animalcreek.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Paul Gortmaker , linux-serial@vger.kernel.org, Dale Farnsworth , linuxppc-dev@lists.ozlabs.org, Christoph Hellwig Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Jun 25, 2019 at 09:37:22AM -0700, Mark Greer wrote: > Yeah, the mpsc driver had lots of ugly cache related hacks because of > cache coherency bugs in the early version of the MV64x60 bridge chips > that it was embedded in. That chip is pretty much dead now and I've > removed core support for it from the powerpc tree. Removing the mpsc > driver is on my todo list but I've been busy and lazy. So, to sum it > up, don't spend any more time worrying about it as it should be removed. > > I'll post a patch to do that tonight and I'm sorry for any time you've > spent looking at it so far. No problem. And if future such broken chips show up we now have support for per-device DMA coherency settings and could actually handle it in a reaѕonably clean way.