Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751148AbdFTM7R (ORCPT ); Tue, 20 Jun 2017 08:59:17 -0400 Received: from foss.arm.com ([217.140.101.70]:37926 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751038AbdFTM7Q (ORCPT ); Tue, 20 Jun 2017 08:59:16 -0400 Subject: Re: [PATCH v5 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU To: hch@lst.de References: <1495621472-9323-1-git-send-email-vladimir.murzin@arm.com> <4e7625ec-54cd-899f-39a7-7cf0c2c8cb26@arm.com> <20170608162555.GP4902@n2100.armlinux.org.uk> Cc: gregkh@linuxfoundation.org, Mark Rutland , Joerg Roedel , sza@esh.hu, arnd@arndb.de, alexandre.torgue@st.com, linux-kernel@vger.kernel.org, Russell King - ARM Linux , Michal Nazarewicz , Yoshinori Sato , Christian Borntraeger , Doug Ledford , Rich Felker , Alan Stern , kbuild-all@01.org, benjamin.gaignard@linaro.org, Rob Herring , akpm@linux-foundation.org, Marek Szyprowski , robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, Roger Quadros From: Vladimir Murzin Message-ID: <2ac09633-cfa8-f941-dc35-4e903b2b8a13@arm.com> Date: Tue, 20 Jun 2017 13:59:10 +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: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6031 Lines: 150 +Christoph since he is trying to consolidate work in this area [1]. Christoph, any chance you can look into patches touching dma-{coherent,noop}.c? [1] https://patchwork.ozlabs.org/patch/778254/ Thanks! Vladimir On 15/06/17 08:25, Vladimir Murzin wrote: > Greg? > > On 08/06/17 17:25, Russell King - ARM Linux wrote: >> Well, I've no objection to this, but it does need acks from other >> people before I can apply it. >> >> There's two patches that touch drivers/base that need Greg's ack. >> >> I'm not sure what's happening with lib/dma-noop.c, there doesn't >> appear to be a maintainer list for it, so I guess that's a >> free-for-all. >> >> On Thu, Jun 08, 2017 at 09:28:30AM +0100, Vladimir Murzin wrote: >>> Ping! >>> >>> On 24/05/17 11:24, Vladimir Murzin wrote: >>>> Short story: >>>> >>>> Without these patches coherent DMA is broken for Andr?s and Alexandre, >>>> so they cannot safely enable DMA on their platforms. >>>> >>>> Patches have been circulated on a list since last year without much >>>> attention to changes in dma-coherent.c and dma-noop.c. Meanwhile, ARM >>>> bits have been reviewed and there is no strict objection to get them >>>> merged. Unfortunately, applying only ARM bits doesn't help much and >>>> the original issue would still exist. >>>> >>>> Please, let me know how to move with this fix forward? >>>> >>>> Long story: >>>> >>>> It seems 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 versions 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 any 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 at 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: >>>> v4 -> v5 >>>> - rebased on v4.12-rc2 >>>> - updated description for CONFIG_ARM_DMA_MEM_BUFFERABLE >>>> >>>> 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 | 8 +- >>>> 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, 359 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 >