Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A266AC43219 for ; Fri, 31 Dec 2021 16:04:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231248AbhLaQEq (ORCPT ); Fri, 31 Dec 2021 11:04:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229503AbhLaQEo (ORCPT ); Fri, 31 Dec 2021 11:04:44 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2807DC061574; Fri, 31 Dec 2021 08:04:44 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E78B2B81D9B; Fri, 31 Dec 2021 16:04:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B56E0C36AF4; Fri, 31 Dec 2021 16:04:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1640966681; bh=pu3EOtLhubDoxaVwiYbh4e/NfH+lhjOkYe7VbmME5Z0=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=raXMVpPTRAf3vF8B62lkOgsA/cVfsPOPEGtrByVh26tgU6FewLliwwvE5oVSxTfvJ 1isY+reYV6wkTVj9kZeXXITYA4ZLSnegTHP2FPOPl+zVGpV7aOvkSmkBLyhNAOgHR1 2sxK+Ewu9K8opb6D6pVml2o8615MS9DLn+olxHqwVzvT8Xh5P7+RRwmCSJfOODKM51 uCDoa4le3AzkzvHOK55tCCwn96EKQBOHpr853njIbdmLrUqgvOFCO+ErxSuQhW1ZUE /E5E7A34ZTJ7Vtr7fXqJFcLl8V4bz4PcNAUhmkNNyPOu/FhFcut4rQ7dYvKY+75A6Q F+kxB9VuFSY/g== Received: by mail-lf1-f50.google.com with SMTP id h2so50380521lfv.9; Fri, 31 Dec 2021 08:04:41 -0800 (PST) X-Gm-Message-State: AOAM532KKP2lW9+vigWtiFAVx+ScumiyAxB4mgB6XqwFtA2NIAGwSqYP /MOKLXDGej5zOzL+XyY78CNLeGxPzFIzBbu32fc= X-Google-Smtp-Source: ABdhPJzApDVGjcuVEHw18tz1R9gDPlbk/Ui+m3pYQWhrQTDSy0tEhDoMzOEccUFjcDO7rPU48bSeyrks7IEcpaugXLU= X-Received: by 2002:adf:f051:: with SMTP id t17mr29442418wro.192.1640966669503; Fri, 31 Dec 2021 08:04:29 -0800 (PST) MIME-Version: 1.0 References: <20211227164317.4146918-1-schnelle@linux.ibm.com> <20211227164317.4146918-3-schnelle@linux.ibm.com> <1f90f145-219e-1cad-6162-9959d43a27ad@gmail.com> <0211719b-8402-9865-8e5d-5c0a35715816@gmail.com> In-Reply-To: <0211719b-8402-9865-8e5d-5c0a35715816@gmail.com> From: Arnd Bergmann Date: Fri, 31 Dec 2021 11:04:12 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC 02/32] Kconfig: introduce HAS_IOPORT option and select it as necessary To: Michael Schmitz Cc: Geert Uytterhoeven , Niklas Schnelle , Bjorn Helgaas , John Garry , Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , Dinh Nguyen , Chris Zankel , Karol Gugala , Jeff Dike , Yoshinori Sato , Brian Cain , Heiko Carstens , Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Russell King , Catalin Marinas , Will Deacon , Michal Simek , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Rich Felker , "David S. Miller" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "the arch/x86 maintainers" , "H. Peter Anvin" , Linux Kernel Mailing List , linux-arch , linux-pci , linux-riscv , linux-csky@vger.kernel.org, "open list:TENSILICA XTENSA PORT (xtensa)" , Openrisc , linux-s390 , alpha , "open list:SYNOPSYS ARC ARCHITECTURE" , Linux ARM , linux-ia64@vger.kernel.org, linux-m68k , "open list:BROADCOM NVRAM DRIVER" , Parisc List , linuxppc-dev , Linux-sh list , sparclinux , Greg Ungerer Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 29, 2021 at 10:44 PM Michael Schmitz wrote: > Am 30.12.2021 um 14:48 schrieb Arnd Bergmann: > > On Tue, Dec 28, 2021 at 11:15 PM Michael Schmitz wrote: > > What some other architectures do is to rely on inb()/outb() to have a > > zero-based offset, and use an io_offset in PCI buses to ensure that a > > low port number on the bus gets translated into a pointer value for the > > virtual mapping in the kernel, which is then represented as an unsigned > > int. > > M54xx does just that for Coldfire: > > arch/m68k/include/asm/io_no.h: > #define PCI_IO_PA 0xf8000000 /* Host physical address */ > > (used to set PCI BAR mappings, so matches your definition above). I think coldfire gets it right here, using PCI_IOBASE to find the start of the window and a zero io_offset: #define PCI_IOBASE ((void __iomem *) PCI_IO_PA) > All other (MMU) m68k users of inb()/outb() apply an io_offset in the > platform specific address translation: > > arch/m68k/include/asm/io_mm.h: > > #define q40_isa_io_base 0xff400000 > #define enec_isa_read_base 0xfffa0000 > #define enec_isa_write_base 0xfffb0000 > > arch/m68k/include/asm/amigayle.h: > > #define GAYLE_IO (0xa20000+zTwoBase) /* 16bit and > even 8bit registers */ > #define GAYLE_IO_8BITODD (0xa30000+zTwoBase) /* odd 8bit > registers */ > > (all constants used in address translation inlines that are used by the > m68k inb()/outb() macros - you can call that the poor man's version of > PCI BAR mappings ...). This still looks like the same thing to me, where you have inb() take a zero-based port number, not a pointer. The effect is the same as the coldfire version, it just uses a custom inline function instead of the version from asm-generic/io.h. > So as long as support for any of the m68k PCI or ISA bridges is selected > in the kernel config, the appropriate IO space mapping is applied. If no > support for PCI or ISA bridges is selected, we already fall back to zero > offset mapping (but as far as I can tell, it shouldn't be possible to > build a kernel without bridge support but drivers that require it). Right. > > As this is indistinguishable from architectures that just don't have > > a base address for I/O ports (we unfortunately picked 0 as the default > > PCI_IOBASE value), my suggestion was to start marking architectures > > that may have this problem as using HAS_IOPORT in order to keep > > the existing behavior unchanged. If m68k does not suffer from this, > > making HAS_IOPORT conditional on those config options that actually > > need it would of course be best. > > Following your description, HAS_IOPORT would be required for neither of > PCI, ISA or ATARI_ROM_ISA ?? For these three options, we definitely need HAS_IOPORT, which would imply that some version of inb()/outb() is provided. The difference between using a custom PCI_IOBASE (or an open-coded equivalent) and using a zero PCI_IOBASE in combination with registering PCI using a custom io_offset is whether we can use drivers with hardcoded port numbers. These should depend on a different Kconfig symbol to be introduced (CONFIG_HARDCODED_IOPORT or similar) once we introduce them, and you could decide for m68k whether to allow those or not, I would assume you do want them in order to use certain legacy ISA drivers. Arnd