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_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,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 D9BDDC4321E for ; Fri, 7 Sep 2018 03:05:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8ED5C2083D for ; Fri, 7 Sep 2018 03:05:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8ED5C2083D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-sky.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726945AbeIGHoC (ORCPT ); Fri, 7 Sep 2018 03:44:02 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:56942 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726434AbeIGHoC (ORCPT ); Fri, 7 Sep 2018 03:44:02 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07716261|-1;CH=green;FP=0|0|0|0|0|-1|-1|-1;HT=e02c03309;MF=ren_guo@c-sky.com;NM=1;PH=DS;RN=11;RT=11;SR=0;TI=SMTPD_---.CnW3XSL_1536289489; Received: from localhost(mailfrom:ren_guo@c-sky.com fp:SMTPD_---.CnW3XSL_1536289489) by smtp.aliyun-inc.com(10.147.42.197); Fri, 07 Sep 2018 11:04:49 +0800 Date: Fri, 7 Sep 2018 11:04:49 +0800 From: Guo Ren To: Arnd Bergmann Cc: linux-arch , Linux Kernel Mailing List , Thomas Gleixner , Daniel Lezcano , Jason Cooper , c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, Thomas Petazzoni , wbx@uclibc-ng.org, Greentime Hu Subject: Re: [PATCH V3 06/26] csky: Cache and TLB routines Message-ID: <20180907030447.GA10434@guoren-Inspiron-7460> References: <16105a3e54f1c4bb65a5ec81d77af7c176e705c6.1536138304.git.ren_guo@c-sky.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2018 at 04:31:16PM +0200, Arnd Bergmann wrote: > On Wed, Sep 5, 2018 at 2:08 PM Guo Ren wrote: > > > diff --git a/arch/csky/include/asm/io.h b/arch/csky/include/asm/io.h > > new file mode 100644 > > index 0000000..fcb2142 > > --- /dev/null > > +++ b/arch/csky/include/asm/io.h > > @@ -0,0 +1,23 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. > > +#ifndef __ASM_CSKY_IO_H > > +#define __ASM_CSKY_IO_H > > + > > +#include > > +#include > > +#include > > + > > +extern void __iomem *ioremap(phys_addr_t offset, size_t size); > > + > > +extern void iounmap(void *addr); > > + > > +extern int remap_area_pages(unsigned long address, phys_addr_t phys_addr, > > + size_t size, unsigned long flags); > > + > > +#define ioremap_nocache(phy, sz) ioremap(phy, sz) > > +#define ioremap_wc ioremap_nocache > > +#define ioremap_wt ioremap_nocache > > + > > +#include > > It is very unusual for an architecture to not need special handling in asm/io.h, > to do the proper barriers etc. > > Can you describe how C-Sky hardware implements MMIO? Our mmio is uncachable and strong-order address, so there is no need barriers for access these io addr. #define ioremap_wc ioremap_nocache #define ioremap_wt ioremap_nocache Current ioremap_wc and ioremap_wt implementation are too simple and we'll improve it in future. > In particular: > > - Is a read from uncached memory always serialized with DMA, and with > other CPUs doing MMIO access to a different address? CPU use ld.w to get data from uncached strong order memory. Other CPUs use the same mmio vaddr to access the uncachable strong order memory paddr. > - How does endianess work? Are there any buses that flip bytes around > when running big-endian, or do you always do that in software? Currently we only support little-endian and soc will follow it. Guo Ren