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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 BA708C17440 for ; Tue, 12 Nov 2019 14:06:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B73C21E6F for ; Tue, 12 Nov 2019 14:06:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727221AbfKLOGh (ORCPT ); Tue, 12 Nov 2019 09:06:37 -0500 Received: from verein.lst.de ([213.95.11.211]:55964 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726497AbfKLOGh (ORCPT ); Tue, 12 Nov 2019 09:06:37 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id 4587368BE1; Tue, 12 Nov 2019 15:06:32 +0100 (CET) Date: Tue, 12 Nov 2019 15:06:31 +0100 From: Christoph Hellwig To: Daniel Vetter Cc: Christoph Hellwig , Arnd Bergmann , Bartlomiej Zolnierkiewicz , X86 ML , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , linux-ia64@vger.kernel.org, Tony Luck , Fenghua Yu , Maarten Lankhorst , Souptick Joarder , dri-devel , Linux Fbdev development list , Linux Kernel Mailing List , Luis Chamberlain , Tuowen Zhao , Mika Westerberg , Andy Shevchenko Subject: Re: [PATCH] video: fbdev: atyfb: only use ioremap_uc() on i386 and ia64 Message-ID: <20191112140631.GA10922@lst.de> References: <20191111192258.2234502-1-arnd@arndb.de> <20191112105507.GA7122@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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, Nov 12, 2019 at 02:04:16PM +0100, Daniel Vetter wrote: > Wut ... Maybe I'm missing something, but from how we use mtrr in other > gpu drivers it's a) either you use MTRR because that's all you got or > b) you use pat. Mixing both sounds like a pretty bad idea, since if > you need MTRR for performance (because you dont have PAT) then you > can't fix the wc with the PAT-based ioremap_uc. And if you have PAT, > then you don't really need an MTRR to get wc. > > So I'd revert this patch from Luis and ... Sounds great to me.. > ... apply this one. Since the same reasoning should apply to anything > that's running on any cpu with PAT. Can you take a look at "mfd: intel-lpss: Use devm_ioremap_uc for MMIO" in linux-next, which also looks rather fishy to me? Can't we use the MTRR APIs to override the broken BIOS MTRR setup there as well? With that we could kill ioremap_uc entirely. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Tue, 12 Nov 2019 14:06:31 +0000 Subject: Re: [PATCH] video: fbdev: atyfb: only use ioremap_uc() on i386 and ia64 Message-Id: <20191112140631.GA10922@lst.de> List-Id: References: <20191111192258.2234502-1-arnd@arndb.de> <20191112105507.GA7122@lst.de> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Daniel Vetter Cc: Christoph Hellwig , Arnd Bergmann , Bartlomiej Zolnierkiewicz , X86 ML , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , linux-ia64@vger.kernel.org, Tony Luck , Fenghua Yu , Maarten Lankhorst , Souptick Joarder , dri-devel , Linux Fbdev development list , Linux Kernel Mailing List , Luis Chamberlain , Tuowen Zhao , Mika Westerberg , Andy Shevchenko On Tue, Nov 12, 2019 at 02:04:16PM +0100, Daniel Vetter wrote: > Wut ... Maybe I'm missing something, but from how we use mtrr in other > gpu drivers it's a) either you use MTRR because that's all you got or > b) you use pat. Mixing both sounds like a pretty bad idea, since if > you need MTRR for performance (because you dont have PAT) then you > can't fix the wc with the PAT-based ioremap_uc. And if you have PAT, > then you don't really need an MTRR to get wc. > > So I'd revert this patch from Luis and ... Sounds great to me.. > ... apply this one. Since the same reasoning should apply to anything > that's running on any cpu with PAT. Can you take a look at "mfd: intel-lpss: Use devm_ioremap_uc for MMIO" in linux-next, which also looks rather fishy to me? Can't we use the MTRR APIs to override the broken BIOS MTRR setup there as well? With that we could kill ioremap_uc entirely. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] video: fbdev: atyfb: only use ioremap_uc() on i386 and ia64 Date: Tue, 12 Nov 2019 15:06:31 +0100 Message-ID: <20191112140631.GA10922@lst.de> References: <20191111192258.2234502-1-arnd@arndb.de> <20191112105507.GA7122@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Daniel Vetter Cc: Christoph Hellwig , Arnd Bergmann , Bartlomiej Zolnierkiewicz , X86 ML , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , linux-ia64@vger.kernel.org, Tony Luck , Fenghua Yu , Maarten Lankhorst , Souptick Joarder , dri-devel , Linux Fbdev development list , Linux Kernel Mailing List , Luis Chamberlain , Tuowen Zhao , Mika Westerberg , Andy Shevchenko List-Id: dri-devel@lists.freedesktop.org On Tue, Nov 12, 2019 at 02:04:16PM +0100, Daniel Vetter wrote: > Wut ... Maybe I'm missing something, but from how we use mtrr in other > gpu drivers it's a) either you use MTRR because that's all you got or > b) you use pat. Mixing both sounds like a pretty bad idea, since if > you need MTRR for performance (because you dont have PAT) then you > can't fix the wc with the PAT-based ioremap_uc. And if you have PAT, > then you don't really need an MTRR to get wc. > > So I'd revert this patch from Luis and ... Sounds great to me.. > ... apply this one. Since the same reasoning should apply to anything > that's running on any cpu with PAT. Can you take a look at "mfd: intel-lpss: Use devm_ioremap_uc for MMIO" in linux-next, which also looks rather fishy to me? Can't we use the MTRR APIs to override the broken BIOS MTRR setup there as well? With that we could kill ioremap_uc entirely. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Tue, 12 Nov 2019 14:06:31 +0000 Subject: Re: [PATCH] video: fbdev: atyfb: only use ioremap_uc() on i386 and ia64 Message-Id: <20191112140631.GA10922@lst.de> List-Id: References: <20191111192258.2234502-1-arnd@arndb.de> <20191112105507.GA7122@lst.de> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Daniel Vetter Cc: Christoph Hellwig , Arnd Bergmann , Bartlomiej Zolnierkiewicz , X86 ML , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , linux-ia64@vger.kernel.org, Tony Luck , Fenghua Yu , Maarten Lankhorst , Souptick Joarder , dri-devel , Linux Fbdev development list , Linux Kernel Mailing List , Luis Chamberlain , Tuowen Zhao , Mika Westerberg , Andy Shevchenko On Tue, Nov 12, 2019 at 02:04:16PM +0100, Daniel Vetter wrote: > Wut ... Maybe I'm missing something, but from how we use mtrr in other > gpu drivers it's a) either you use MTRR because that's all you got or > b) you use pat. Mixing both sounds like a pretty bad idea, since if > you need MTRR for performance (because you dont have PAT) then you > can't fix the wc with the PAT-based ioremap_uc. And if you have PAT, > then you don't really need an MTRR to get wc. > > So I'd revert this patch from Luis and ... Sounds great to me.. > ... apply this one. Since the same reasoning should apply to anything > that's running on any cpu with PAT. Can you take a look at "mfd: intel-lpss: Use devm_ioremap_uc for MMIO" in linux-next, which also looks rather fishy to me? Can't we use the MTRR APIs to override the broken BIOS MTRR setup there as well? With that we could kill ioremap_uc entirely.