From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764918AbdEWUFL (ORCPT ); Tue, 23 May 2017 16:05:11 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:54682 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758664AbdEWUFJ (ORCPT ); Tue, 23 May 2017 16:05:09 -0400 Date: Tue, 23 May 2017 21:04:39 +0100 From: Russell King - ARM Linux To: Vladimir Murzin Cc: linux-arm-kernel@lists.infradead.org, Mark Rutland , Joerg Roedel , sza@esh.hu, Yoshinori Sato , alexandre.torgue@st.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Michal Nazarewicz , Christian Borntraeger , Doug Ledford , Rich Felker , arnd@arndb.de, kbuild-all@01.org, Rob Herring , Alan Stern , akpm@linux-foundation.org, Marek Szyprowski , robin.murphy@arm.com, Roger Quadros Subject: Re: [PATCH v4 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU Message-ID: <20170523200439.GE22219@n2100.armlinux.org.uk> References: <1493029017-31382-1-git-send-email-vladimir.murzin@arm.com> <4486fe6f-d8d8-2ad6-a724-8ae74dd33f56@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 On Mon, May 15, 2017 at 09:52:58AM +0100, Vladimir Murzin wrote: > Ping again... Apart from the one comment, the ARM bits look fine to me - but I'm not saying anything about the lib/dma-noop.c or the drivers/base changes. What's the dependency between the ARM bits and those bits? > On 02/05/17 09:32, Vladimir Murzin wrote: > > Gentle ping! > > > > On 24/04/17 11:16, Vladimir Murzin wrote: > >> It seem that addition of cache support for M-class CPUs uncovered > >> latent bug in DMA usage. NOMMU memory model has been treated as being > >> always consistent; however, for R/M CPU classes memory can be covered > >> by MPU which in turn might configure RAM as Normal i.e. bufferable and > >> cacheable. It breaks dma_alloc_coherent() and friends, since data can > >> stuck in caches now or be buffered. > >> > >> This patch set is trying to address the issue by providing region of > >> memory suitable for consistent DMA operations. It is supposed that > >> such region is marked by MPU as non-cacheable. Robin suggested to > >> advertise such memory as reserved shared-dma-pool, rather then using > >> homebrew command line option, and extend dma-coherent to provide > >> default DMA area in the similar way as it is done for CMA (PATCH > >> 4/7). It allows us to offload all bookkeeping on generic coherent DMA > >> framework, and it seems that it might be reused by other architectures > >> like c6x and blackfin. > >> > >> While reviewing/testing previous vesrions of the patch set it turned > >> out that dma-coherent does not take into account "dma-ranges" device > >> tree property, so it is addressed in PATCH 3/7. > >> > >> For ARM, dedicated DMA region is required for cases other than: > >> - MMU/MPU is off > >> - cpu is v7m w/o cache support > >> - device is coherent > >> > >> In case one of the above conditions is true dma operations are forced > >> to be coherent and wired with dma_noop_ops. > >> > >> To make life easier NOMMU dma operations are kept in separate > >> compilation unit. > >> > >> Since the issue was reported in the same time as Benjamin sent his > >> patch [1] to allow mmap for NOMMU, his case is also addressed in this > >> series (PATCH 1/7 and PATCH 2/7). > >> > >> Thanks! > >> > >> [1] http://www.armlinux.org.uk/developer/patches/viewpatch.php?id=8633/1 > >> > >> Cc: Joerg Roedel > >> Cc: Christian Borntraeger > >> Cc: Michal Nazarewicz > >> Cc: Marek Szyprowski > >> Cc: Alan Stern > >> Cc: Yoshinori Sato > >> Cc: Rich Felker > >> Cc: Roger Quadros > >> Cc: Greg Kroah-Hartman > >> Cc: Rob Herring > >> Cc: Mark Rutland > >> Cc: Doug Ledford > >> > >> Changelog: > >> v3 -> v4 > >> - rebased on v4.11-rc7 > >> - made CONFIG_ARM_DMA_MEM_BUFFERABLE optional for CPU_V7M > >> - added Arnd's Acked-by > >> > >> v2 -> v3 > >> - fixed warnings reported by Alexandre and kbuild robot > >> > >> v1 -> v2 > >> - rebased on v4.11-rc1 > >> - added Robin's Reviewed-by > >> - dedicated flag is introduced to use dev->dma_pfn_offset > >> rather than mem->device_base in case memory region is > >> configured via device tree (so Tested-by discarded there) > >> > >> RFC v6 -> v1 > >> - dropped RFC tag > >> - added Alexandre's Tested-by > >> > >> > >> Vladimir Murzin (7): > >> dma: Take into account dma_pfn_offset > >> dma: Add simple dma_noop_mmap > >> drivers: dma-coherent: Account dma_pfn_offset when used with device > >> tree > >> drivers: dma-coherent: Introduce default DMA pool > >> ARM: NOMMU: Introduce dma operations for noMMU > >> ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus > >> ARM: dma-mapping: Remove traces of NOMMU code > >> > >> .../bindings/reserved-memory/reserved-memory.txt | 3 + > >> arch/arm/Kconfig | 1 + > >> arch/arm/include/asm/dma-mapping.h | 2 +- > >> arch/arm/mm/Kconfig | 4 +- > >> arch/arm/mm/Makefile | 5 +- > >> arch/arm/mm/dma-mapping-nommu.c | 253 +++++++++++++++++++++ > >> arch/arm/mm/dma-mapping.c | 29 +-- > >> drivers/base/dma-coherent.c | 74 +++++- > >> lib/dma-noop.c | 29 ++- > >> 9 files changed, 355 insertions(+), 45 deletions(-) > >> create mode 100644 arch/arm/mm/dma-mapping-nommu.c > >> > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > > -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.