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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 0F063C433E0 for ; Wed, 15 Jul 2020 02:25:02 +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 B5B3020729 for ; Wed, 15 Jul 2020 02:25:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B5B3020729 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4B61SC58Y8zDqQt for ; Wed, 15 Jul 2020 12:24:59 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=permerror (SPF Permanent Error: Unknown mechanism found: ip:192.40.192.88/32) smtp.mailfrom=kernel.crashing.org (client-ip=76.164.61.194; helo=kernel.crashing.org; envelope-from=benh@kernel.crashing.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Received: from kernel.crashing.org (kernel.crashing.org [76.164.61.194]) (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 4B61NN2F9lzDqbw for ; Wed, 15 Jul 2020 12:21:39 +1000 (AEST) Received: from localhost (gate.crashing.org [63.228.1.57]) (authenticated bits=0) by kernel.crashing.org (8.14.7/8.14.7) with ESMTP id 06F2JlC0001315 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 14 Jul 2020 21:19:51 -0500 Message-ID: <2629240c07af7fec5989127ed6da405e12cf77a3.camel@kernel.crashing.org> Subject: Re: [RFC PATCH 00/35] Move all PCIBIOS* definitions into arch/x86 From: Benjamin Herrenschmidt To: Bjorn Helgaas , Arnd Bergmann Date: Wed, 15 Jul 2020 12:19:46 +1000 In-Reply-To: <20200714234625.GA428442@bjorn-Precision-5520> References: <20200714234625.GA428442@bjorn-Precision-5520> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit 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: linux-pci , Keith Busch , Paul Mackerras , sparclinux , Toan Le , Kjetil Oftedal , Greg Ungerer , Marek Vasut , Rob Herring , Lorenzo Pieralisi , Sagi Grimberg , Russell King , Ley Foon Tan , Christoph Hellwig , Geert Uytterhoeven , Kevin Hilman , Jakub Kicinski , Matt Turner , linux-kernel-mentees@lists.linuxfoundation.org, Guenter Roeck , Ray Jui , Jens Axboe , Ivan Kokshaysky , Shuah Khan , bjorn@helgaas.com, Boris Ostrovsky , Richard Henderson , Juergen Gross , Bjorn Helgaas , Thomas Bogendoerfer , Scott Branden , Jingoo Han , "Saheed O. Bolarinwa" , "linux-kernel@vger.kernel.org" , Philipp Zabel , Greg Kroah-Hartman , Gustavo Pimentel , linuxppc-dev , "David S. Miller" , Heiner Kallweit Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, 2020-07-14 at 18:46 -0500, Bjorn Helgaas wrote: > Yes. I have no problem with that. There are a few cases where it's > important to check for errors, e.g., we read a status register and do > something based on a bit being set. A failure will return all bits > set, and we may do the wrong thing. But most of the errors we care > about will be on MMIO reads, not config reads, so we can probably > ignore most config read errors. And in both cases, we don't have the plumbing to provide accurate and reliable error returns for all platforms anyways (esp. not for MMIO). I think it makes sense to stick to the good old "if all 1's, then go out of line" including for config space. ../.. > Yep, except for things like device removal or other PCI errors. A whole bunch of these are reported asynchronously, esp for writes (and yes, including config writes, they are supposed to be non-posted but more often than not, the path from the CPU to the PCI bridge remains posted for writes including config ones). > So maybe a good place to start is by removing some of the useless > error checking for pci_read_config_*() and pci_write_config_*(). > That's a decent-sized but not impractical project that could be done > per subsystem or something: > > git grep -E "(if|return|=).*\ > finds about 400 matches. > > Some of those callers probably really *do* want to check for errors, > and I guess we'd have to identify them and do them separately as you > mentioned. I'd be curious about these considering how unreliable our error return is accross the board. Cheers, Ben.