From patchwork Tue Sep 15 15:51:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 11777931 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 373506CA for ; Tue, 15 Sep 2020 22:19:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18741208E4 for ; Tue, 15 Sep 2020 22:19:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DkmB3YTM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727443AbgIOWT1 (ORCPT ); Tue, 15 Sep 2020 18:19:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727690AbgIOQ3r (ORCPT ); Tue, 15 Sep 2020 12:29:47 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 543DBC061A10; Tue, 15 Sep 2020 09:11:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=I03vZyMCQXixsKgB+vAi29QqwSDPgVkGV9+ViaS1CMg=; b=DkmB3YTM4x4P/03PR0YpgL495M EfAecJ6/RbGViN36w0QSd/Tr391/7C3qp+8l6E51mioxfYFEf84qweB7rrRnnk+XS4NrRJAxVL9or eM1zmit6nOvg6b55NFhpo114VioVSvnslqOCa1VQJwriMKfnb1O5WFoJuez65V/sByOexHLk1aG12 kIJoLn37eUqAXIXtLeRRXw1BLM962vL4dorybD0panUqncIhUNKnleKBHKVtAPesBxrCrYXQozSDG Ht+YUL90n+pvTplQ82CtOCFOCta92rwWzKpTg+cQVDksvP2loDwB8A2oyP92wwnyQJsL9Bj01w7CB wY2hcvmw==; Received: from 089144214092.atnat0023.highway.a1.net ([89.144.214.92] helo=localhost) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kIDXq-0004bk-Fp; Tue, 15 Sep 2020 16:11:02 +0000 From: Christoph Hellwig To: Mauro Carvalho Chehab , Thomas Bogendoerfer , "James E.J. Bottomley" , Joonyoung Shim , Seung-Woo Kim , Ben Skeggs , Marek Szyprowski , Tomasz Figa , Matt Porter , iommu@lists.linux-foundation.org Cc: Stefan Richter , linux1394-devel@lists.sourceforge.net, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-samsung-soc@vger.kernel.org, nouveau@lists.freedesktop.org, netdev@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org, alsa-devel@alsa-project.org Subject: [PATCH 08/18] dma-mapping: add a new dma_alloc_noncoherent API Date: Tue, 15 Sep 2020 17:51:12 +0200 Message-Id: <20200915155122.1768241-9-hch@lst.de> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200915155122.1768241-1-hch@lst.de> References: <20200915155122.1768241-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Add a new API to allocate and free memory that is guaranteed to be addressable by a device, but which potentially is not cache coherent for DMA. To transfer ownership to and from the device, the existing streaming DMA API calls dma_sync_single_for_device and dma_sync_single_for_cpu must be used. For now the new calls are implemented on top of dma_alloc_attrs just like the old-noncoherent API, but once all drivers are switched to the new API it will be replaced with a better working implementation that is available on all architectures. Signed-off-by: Christoph Hellwig --- Documentation/core-api/dma-api.rst | 75 ++++++++++++++---------------- include/linux/dma-mapping.h | 12 +++++ 2 files changed, 48 insertions(+), 39 deletions(-) diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst index 90239348b30f6f..ea0413276ddb70 100644 --- a/Documentation/core-api/dma-api.rst +++ b/Documentation/core-api/dma-api.rst @@ -516,48 +516,56 @@ routines, e.g.::: } -Part II - Advanced dma usage ----------------------------- +Part II - Non-coherent DMA allocations +-------------------------------------- -Warning: These pieces of the DMA API should not be used in the -majority of cases, since they cater for unlikely corner cases that -don't belong in usual drivers. +These APIs allow to allocate pages in the kernel direct mapping that are +guaranteed to be DMA addressable. This means that unlike dma_alloc_coherent, +virt_to_page can be called on the resulting address, and the resulting +struct page can be used for everything a struct page is suitable for. -If you don't understand how cache line coherency works between a -processor and an I/O device, you should not be using this part of the -API at all. +If you don't understand how cache line coherency works between a processor and +an I/O device, you should not be using this part of the API. :: void * - dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle, - gfp_t flag, unsigned long attrs) + dma_alloc_noncoherent(struct device *dev, size_t size, + dma_addr_t *dma_handle, enum dma_data_direction dir, + gfp_t gfp) -Identical to dma_alloc_coherent() except that when the -DMA_ATTR_NON_CONSISTENT flags is passed in the attrs argument, the -platform will choose to return either consistent or non-consistent memory -as it sees fit. By using this API, you are guaranteeing to the platform -that you have all the correct and necessary sync points for this memory -in the driver should it choose to return non-consistent memory. +This routine allocates a region of bytes of consistent memory. It +returns a pointer to the allocated region (in the processor's virtual address +space) or NULL if the allocation failed. The returned memory may or may not +be in the kernels direct mapping. Drivers must not call virt_to_page on +the returned memory region. -Note: where the platform can return consistent memory, it will -guarantee that the sync points become nops. +It also returns a which may be cast to an unsigned integer the +same width as the bus and given to the device as the DMA address base of +the region. -Warning: Handling non-consistent memory is a real pain. You should -only use this API if you positively know your driver will be -required to work on one of the rare (usually non-PCI) architectures -that simply cannot make consistent memory. +The dir parameter specified if data is read and/or written by the device, +see dma_map_single() for details. + +The gfp parameter allows the caller to specify the ``GFP_`` flags (see +kmalloc()) for the allocation, but rejects flags used to specify a memory +zone such as GFP_DMA or GFP_HIGHMEM. + +Before giving the memory to the device, dma_sync_single_for_device() needs +to be called, and before reading memory written by the device, +dma_sync_single_for_cpu(), just like for streaming DMA mappings that are +reused. :: void - dma_free_attrs(struct device *dev, size_t size, void *cpu_addr, - dma_addr_t dma_handle, unsigned long attrs) + dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr, + dma_addr_t dma_handle, enum dma_data_direction dir) -Free memory allocated by the dma_alloc_attrs(). All common -parameters must be identical to those otherwise passed to dma_free_coherent, -and the attrs argument must be identical to the attrs passed to -dma_alloc_attrs(). +Free a region of memory previously allocated using dma_alloc_noncoherent(). +dev, size and dma_handle and dir must all be the same as those passed into +dma_alloc_noncoherent(). cpu_addr must be the virtual address returned by +the dma_alloc_noncoherent(). :: @@ -575,17 +583,6 @@ memory or doing partial flushes. into the width returned by this call. It will also always be a power of two for easy alignment. -:: - - void - dma_cache_sync(struct device *dev, void *vaddr, size_t size, - enum dma_data_direction direction) - -Do a partial sync of memory that was allocated by dma_alloc_attrs() with -the DMA_ATTR_NON_CONSISTENT flag starting at virtual address vaddr and -continuing on for size. Again, you *must* observe the cache line -boundaries when doing this. - Part III - Debug drivers use of the DMA-API ------------------------------------------- diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index df0bff2ea750e0..4e1de194b45cbf 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -389,6 +389,18 @@ static inline unsigned long dma_get_merge_boundary(struct device *dev) } #endif /* CONFIG_HAS_DMA */ +static inline void *dma_alloc_noncoherent(struct device *dev, size_t size, + dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp) +{ + return dma_alloc_attrs(dev, size, dma_handle, gfp, + DMA_ATTR_NON_CONSISTENT); +} +static inline void dma_free_noncoherent(struct device *dev, size_t size, + void *vaddr, dma_addr_t dma_handle, enum dma_data_direction dir) +{ + dma_free_attrs(dev, size, vaddr, dma_handle, DMA_ATTR_NON_CONSISTENT); +} + static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr, size_t size, enum dma_data_direction dir, unsigned long attrs) {