From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933223AbdEOIxT (ORCPT ); Mon, 15 May 2017 04:53:19 -0400 Received: from foss.arm.com ([217.140.101.70]:48826 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932386AbdEOIxQ (ORCPT ); Mon, 15 May 2017 04:53:16 -0400 Subject: Re: [PATCH v4 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU To: linux-arm-kernel@lists.infradead.org References: <1493029017-31382-1-git-send-email-vladimir.murzin@arm.com> <4486fe6f-d8d8-2ad6-a724-8ae74dd33f56@arm.com> Cc: Mark Rutland , Joerg Roedel , sza@esh.hu, Yoshinori Sato , alexandre.torgue@st.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Michal Nazarewicz , linux@armlinux.org.uk, 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 From: Vladimir Murzin Message-ID: Date: Mon, 15 May 2017 09:52:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <4486fe6f-d8d8-2ad6-a724-8ae74dd33f56@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ping again... 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 >