Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752752AbbBEMHk (ORCPT ); Thu, 5 Feb 2015 07:07:40 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:42006 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752444AbbBEMHj (ORCPT ); Thu, 5 Feb 2015 07:07:39 -0500 Date: Thu, 5 Feb 2015 12:07:20 +0000 From: Catalin Marinas To: Graeme Gregory Cc: Ard Biesheuvel , "msalter@redhat.com" , Mark Rutland , Mark Langsdorf , "linaro-acpi@lists.linaro.org" , Will Deacon , "wangyijing@huawei.com" , Rob Herring , Lorenzo Pieralisi , Timur Tabi , Daniel Lezcano , "linux-acpi@vger.kernel.org" , "grant.likely@linaro.org" , Charles Garcia-Tobin , "phoenix.liyi@huawei.com" , Robert Richter , Jason Cooper , Arnd Bergmann , Marc Zyngier , "jcm@redhat.com" , Mark Brown , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" , Ashwin Chaugule , "graeme.gregory@linaro.org" , Randy Dunlap , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , "hanjun.guo@linaro.org" , "suravee.suthikulpanit@amd.com" , Sudeep Holla , Olof Johansson Subject: Re: [PATCH v8 02/21] acpi: fix acpi_os_ioremap for arm64 Message-ID: <20150205120720.GD18158@e104818-lin.cambridge.arm.com> References: <2422968.Es7R0p3loO@vostro.rjw.lan> <1422984576.18187.82.camel@deneb.redhat.com> <20150204112508.GB26006@e104818-lin.cambridge.arm.com> <1423066107.18187.99.camel@deneb.redhat.com> <20150204175734.GI26006@e104818-lin.cambridge.arm.com> <1423076294.18187.103.camel@deneb.redhat.com> <20150205104149.GA18158@e104818-lin.cambridge.arm.com> <20150205105945.GC18158@e104818-lin.cambridge.arm.com> <20150205111443.GC24474@xora-haswell.xora.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150205111443.GC24474@xora-haswell.xora.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3448 Lines: 78 On Thu, Feb 05, 2015 at 11:14:43AM +0000, Graeme Gregory wrote: > On Thu, Feb 05, 2015 at 10:59:45AM +0000, Catalin Marinas wrote: > > On Thu, Feb 05, 2015 at 10:47:23AM +0000, Ard Biesheuvel wrote: > > > On 5 February 2015 at 10:41, Catalin Marinas wrote: > > > > On Wed, Feb 04, 2015 at 06:58:14PM +0000, Mark Salter wrote: > > > >> On Wed, 2015-02-04 at 17:57 +0000, Catalin Marinas wrote: > > > >> > On Wed, Feb 04, 2015 at 04:08:27PM +0000, Mark Salter wrote: > > > >> > > acpi_os_remap() is used to map ACPI tables. These tables may be in ram > > > >> > > which are already included in the kernel's linear RAM mapping. So we > > > >> > > need ioremap_cache to avoid two mappings to the same physical page > > > >> > > having different caching attributes. > > > >> > > > > >> > What's the call path to acpi_os_ioremap() on such tables already in the > > > >> > linear mapping? I can see an acpi_map() function which already takes > > > >> > care of the RAM mapping case but there are other cases where > > > >> > acpi_os_ioremap() is called directly. For example, > > > >> > acpi_os_read_memory(), can it be called on both RAM and I/O? > > > >> > > > >> acpi_map() is the one I've seen. > > > > > > > > By default, if should_use_kmap() is not patched for arm64, it translates > > > > to page_is_ram(); acpi_map() would simply use a kmap() which returns the > > > > current kernel linear mapping on arm64. > > > > > > > >> I'm not sure about others. > > > > > > > > Question for the ARM ACPI guys: what happens if you implement > > > > acpi_os_ioremap() on arm64 as just ioremap()? Do you get any WARN_ON() > > > > (__ioremap_caller() checks whether the memory is RAM)? > > > > > > Regardless of whether you hit any WARN_ON()s now, > > > > Actually following the WARN_ON(), ioremap() returns NULL, so it may not > > go entirely unnoticed. > > > > > we still need to distinguish between MMIO ranges with device > > > semantics, and ACPI or other tables whose data may not be naturally > > > aligned all the time, and hence requiring memory semantics. > > > acpi_os_ioremap() may be used for both, afaik > > > > Is acpi_os_ioremap() called directly (outside acpi_map()) to map RAM > > that already part of the kernel linear memory? If yes, then I agree that > > we need to do such check. > > > > Another question, can we distinguish, in the ACPI core code, whether the > > mapping is for an ACPI table in RAM or some I/O space? > > Yes I think we do, > > acpi_os_map_memory() is called to map tables > > acpi_os_map_iomem() is called to map device IO > > currently both end up in acpi_map but I guess they do not have to or > we can add extra arguments as its an internal API. Ending up in acpi_map() is ok as this function checks whether it should use kmap() or acpi_os_ioremap(). > But I have not checked that no user sneaks in direct calls. Grep'ing for acpi_os_ioremap(): suspend_nvs_save() - we don't care about this yet for arm64 as the function is only compiled in if CONFIG_ACPI_SLEEP acpi_os_read_memory() and acpi_os_write_memory() - do you know what kind of memory are these used on? couple of intel drm files that are not used on arm. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/