From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v7 00/17] Introduce ACPI for ARM64 based on ACPI 5.1 Date: Fri, 16 Jan 2015 16:40:28 +0100 Message-ID: <1809831.d9GPSfLUEN@wuerfel> References: <1421247905-3749-1-git-send-email-hanjun.guo@linaro.org> <2198633.UpIyI82Yon@wuerfel> <20150116153320.GU7091@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: Received: from mout.kundenserver.de ([212.227.17.13]:57249 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752233AbbAPPlV (ORCPT ); Fri, 16 Jan 2015 10:41:21 -0500 In-Reply-To: <20150116153320.GU7091@arm.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: linux-arm-kernel@lists.infradead.org Cc: Will Deacon , Mark Rutland , linaro-acpi , Catalin Marinas , Yijing Wang , Rob Herring , Lorenzo Pieralisi , Timur Tabi , ACPI Devel Mailing List , "grant.likely@linaro.org" , Charles Garcia-Tobin , Tom Lendacky , "phoenix.liyi@huawei.com" , Robert Richter , Jason Cooper , Marc Zyngier , "jcm@redhat.com" , Mark Brown , Bjorn Helgaas , "graeme.gregory@linaro.org" , Randy Dunlap , Rafae On Friday 16 January 2015 15:33:20 Will Deacon wrote: > On Fri, Jan 16, 2015 at 03:14:13PM +0000, Arnd Bergmann wrote: > > On Friday 16 January 2015 14:55:45 Will Deacon wrote: > > > On Fri, Jan 16, 2015 at 02:45:30PM +0000, Tom Lendacky wrote: > > > > I have tested ACPI-enablement patches for the amd-xgbe/amd-xgbe-phy > > > > drivers that I'm about to submit upstream with the V7 patch series > > > > on the AMD Seattle server platform. There does not appear to be support > > > > for the _CCA attribute in this patch series. The amd-xgbe driver will > > > > setup the device domain and cache attributes based on the presence of > > > > this attribute, but it requires the arch support to assign the proper > > > > DMA operations in order for it to all work correctly. > > > > > > > > Overriding the _CCA attribute in the driver, I was able to successfully > > > > test the driver and this patch series. > > > > > > Hopefully this will all be addressed when the IORT parts of ACPI have > > > settled down (the current proposal allows for these attributes to be > > > described as well as their interaction with things like IOMMUs). > > > > > > In the meantime, are you falling back to non-coherent DMA? If so, what > > > attributes have you settled on? We need to be really careful not to > > > corrupt data during cache invalidatation when mapping a non-coherent > > > buffer for the CPU. > > > > I think in case of ACPI we should use cache-coherent as the default, > > as this is what all servers will use for DMA masters. > > I don't agree. The dma-coherent we have for device-tree isn't nearly > expressive enough for the kind of things we want to describe and there's > no reason to make the same mistake in ACPI, especially as it *is* being > addressed by IORT. If we run with _CCA, then we're going to be stuck > supporting something that isn't fit for purpose and which will likely be > abused to describe both fixed features of the system and software > configuration preferences. It also opens up a can of worms if we have to > support a mixture of _CCA and IORT in the future. > > Or are you suggesting that we ignore _CCA and just assume cache-coherency? > In that case, how do we support systems that aren't cache coherent, where > not being cache coherent includes devices that require either device or > IOMMU configuration to enable cacheable transactions? I was thinking we'd ignore _CCA because as you say a simple on/off flag would not be enough to describe what we have to do for noncoherent devices. I can't think of any reason why a server hardware would include noncoherent devices, so if they are configurable they should be configured into coherent mode by the firmware. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756364AbbAPPlW (ORCPT ); Fri, 16 Jan 2015 10:41:22 -0500 Received: from mout.kundenserver.de ([212.227.17.13]:57249 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752233AbbAPPlV (ORCPT ); Fri, 16 Jan 2015 10:41:21 -0500 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Will Deacon , Mark Rutland , linaro-acpi , Catalin Marinas , Yijing Wang , Rob Herring , Lorenzo Pieralisi , Timur Tabi , ACPI Devel Mailing List , "grant.likely@linaro.org" , Charles Garcia-Tobin , Tom Lendacky , "phoenix.liyi@huawei.com" , Robert Richter , Jason Cooper , Marc Zyngier , "jcm@redhat.com" , Mark Brown , Bjorn Helgaas , "graeme.gregory@linaro.org" , Randy Dunlap , "Rafael J. Wysocki" , Linux Kernel Mailing List , "hanjun.guo@linaro.org" , "suravee.suthikulpanit@amd.com" , Sudeep Holla , Olof Johansson Subject: Re: [PATCH v7 00/17] Introduce ACPI for ARM64 based on ACPI 5.1 Date: Fri, 16 Jan 2015 16:40:28 +0100 Message-ID: <1809831.d9GPSfLUEN@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20150116153320.GU7091@arm.com> References: <1421247905-3749-1-git-send-email-hanjun.guo@linaro.org> <2198633.UpIyI82Yon@wuerfel> <20150116153320.GU7091@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:Sx35rvRh5S/2DLa0CMRLfwUgA9MTVpdlu6rn/2L6HahQyeNrOGF jmcvT/zTc12NEzg0+91sMzpn5WWG+ee/Lm0BlBjPnzuC81BCwlrCGyVWvxPsb2ptJdYDgGF UjWZXZVnZfo3oWolwQeEaYyp0o7483p/Af0+Kib8TvqBM5xdUHdKclzSS/egDMhWwKaV4BT oOnNxPU3vabZrEb99wKog== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 16 January 2015 15:33:20 Will Deacon wrote: > On Fri, Jan 16, 2015 at 03:14:13PM +0000, Arnd Bergmann wrote: > > On Friday 16 January 2015 14:55:45 Will Deacon wrote: > > > On Fri, Jan 16, 2015 at 02:45:30PM +0000, Tom Lendacky wrote: > > > > I have tested ACPI-enablement patches for the amd-xgbe/amd-xgbe-phy > > > > drivers that I'm about to submit upstream with the V7 patch series > > > > on the AMD Seattle server platform. There does not appear to be support > > > > for the _CCA attribute in this patch series. The amd-xgbe driver will > > > > setup the device domain and cache attributes based on the presence of > > > > this attribute, but it requires the arch support to assign the proper > > > > DMA operations in order for it to all work correctly. > > > > > > > > Overriding the _CCA attribute in the driver, I was able to successfully > > > > test the driver and this patch series. > > > > > > Hopefully this will all be addressed when the IORT parts of ACPI have > > > settled down (the current proposal allows for these attributes to be > > > described as well as their interaction with things like IOMMUs). > > > > > > In the meantime, are you falling back to non-coherent DMA? If so, what > > > attributes have you settled on? We need to be really careful not to > > > corrupt data during cache invalidatation when mapping a non-coherent > > > buffer for the CPU. > > > > I think in case of ACPI we should use cache-coherent as the default, > > as this is what all servers will use for DMA masters. > > I don't agree. The dma-coherent we have for device-tree isn't nearly > expressive enough for the kind of things we want to describe and there's > no reason to make the same mistake in ACPI, especially as it *is* being > addressed by IORT. If we run with _CCA, then we're going to be stuck > supporting something that isn't fit for purpose and which will likely be > abused to describe both fixed features of the system and software > configuration preferences. It also opens up a can of worms if we have to > support a mixture of _CCA and IORT in the future. > > Or are you suggesting that we ignore _CCA and just assume cache-coherency? > In that case, how do we support systems that aren't cache coherent, where > not being cache coherent includes devices that require either device or > IOMMU configuration to enable cacheable transactions? I was thinking we'd ignore _CCA because as you say a simple on/off flag would not be enough to describe what we have to do for noncoherent devices. I can't think of any reason why a server hardware would include noncoherent devices, so if they are configurable they should be configured into coherent mode by the firmware. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Fri, 16 Jan 2015 16:40:28 +0100 Subject: [PATCH v7 00/17] Introduce ACPI for ARM64 based on ACPI 5.1 In-Reply-To: <20150116153320.GU7091@arm.com> References: <1421247905-3749-1-git-send-email-hanjun.guo@linaro.org> <2198633.UpIyI82Yon@wuerfel> <20150116153320.GU7091@arm.com> Message-ID: <1809831.d9GPSfLUEN@wuerfel> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Friday 16 January 2015 15:33:20 Will Deacon wrote: > On Fri, Jan 16, 2015 at 03:14:13PM +0000, Arnd Bergmann wrote: > > On Friday 16 January 2015 14:55:45 Will Deacon wrote: > > > On Fri, Jan 16, 2015 at 02:45:30PM +0000, Tom Lendacky wrote: > > > > I have tested ACPI-enablement patches for the amd-xgbe/amd-xgbe-phy > > > > drivers that I'm about to submit upstream with the V7 patch series > > > > on the AMD Seattle server platform. There does not appear to be support > > > > for the _CCA attribute in this patch series. The amd-xgbe driver will > > > > setup the device domain and cache attributes based on the presence of > > > > this attribute, but it requires the arch support to assign the proper > > > > DMA operations in order for it to all work correctly. > > > > > > > > Overriding the _CCA attribute in the driver, I was able to successfully > > > > test the driver and this patch series. > > > > > > Hopefully this will all be addressed when the IORT parts of ACPI have > > > settled down (the current proposal allows for these attributes to be > > > described as well as their interaction with things like IOMMUs). > > > > > > In the meantime, are you falling back to non-coherent DMA? If so, what > > > attributes have you settled on? We need to be really careful not to > > > corrupt data during cache invalidatation when mapping a non-coherent > > > buffer for the CPU. > > > > I think in case of ACPI we should use cache-coherent as the default, > > as this is what all servers will use for DMA masters. > > I don't agree. The dma-coherent we have for device-tree isn't nearly > expressive enough for the kind of things we want to describe and there's > no reason to make the same mistake in ACPI, especially as it *is* being > addressed by IORT. If we run with _CCA, then we're going to be stuck > supporting something that isn't fit for purpose and which will likely be > abused to describe both fixed features of the system and software > configuration preferences. It also opens up a can of worms if we have to > support a mixture of _CCA and IORT in the future. > > Or are you suggesting that we ignore _CCA and just assume cache-coherency? > In that case, how do we support systems that aren't cache coherent, where > not being cache coherent includes devices that require either device or > IOMMU configuration to enable cacheable transactions? I was thinking we'd ignore _CCA because as you say a simple on/off flag would not be enough to describe what we have to do for noncoherent devices. I can't think of any reason why a server hardware would include noncoherent devices, so if they are configurable they should be configured into coherent mode by the firmware. Arnd