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=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 97CD0C4646B for ; Wed, 26 Jun 2019 06:49:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 778DE20665 for ; Wed, 26 Jun 2019 06:49:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726807AbfFZGtK (ORCPT ); Wed, 26 Jun 2019 02:49:10 -0400 Received: from verein.lst.de ([213.95.11.211]:40589 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725954AbfFZGtK (ORCPT ); Wed, 26 Jun 2019 02:49:10 -0400 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 Cc: Christoph Hellwig , Paul Gortmaker , Dale Farnsworth , Greg Kroah-Hartman , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.