From patchwork Wed Mar 30 15:39:51 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Boris BREZILLON X-Patchwork-Id: 8698801 Return-Path: X-Original-To: patchwork-dmaengine@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id B5080C0553 for ; Wed, 30 Mar 2016 15:40:39 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 9A0BC20383 for ; Wed, 30 Mar 2016 15:40:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 76E2420386 for ; Wed, 30 Mar 2016 15:40:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754641AbcC3Pk1 (ORCPT ); Wed, 30 Mar 2016 11:40:27 -0400 Received: from down.free-electrons.com ([37.187.137.238]:60572 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754568AbcC3PkC (ORCPT ); Wed, 30 Mar 2016 11:40:02 -0400 Received: by mail.free-electrons.com (Postfix, from userid 110) id AAB4617DF; Wed, 30 Mar 2016 17:39:59 +0200 (CEST) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 Received: from localhost.localdomain (LMontsouris-657-1-184-87.w90-63.abo.wanadoo.fr [90.63.216.87]) by mail.free-electrons.com (Postfix) with ESMTPSA id 09B5517DF; Wed, 30 Mar 2016 17:39:59 +0200 (CEST) From: Boris Brezillon To: David Woodhouse , Brian Norris , linux-mtd@lists.infradead.org, Andrew Morton , Dave Gordon Cc: Mark Brown , linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Maxime Ripard , Chen-Yu Tsai , linux-sunxi@googlegroups.com, Vinod Koul , Dan Williams , dmaengine@vger.kernel.org, Mauro Carvalho Chehab , Hans Verkuil , Laurent Pinchart , linux-media@vger.kernel.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree@vger.kernel.org, Boris Brezillon , Richard Weinberger Subject: [PATCH v2 4/7] scatterlist: add sg_alloc_table_from_buf() helper Date: Wed, 30 Mar 2016 17:39:51 +0200 Message-Id: <1459352394-22810-5-git-send-email-boris.brezillon@free-electrons.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1459352394-22810-1-git-send-email-boris.brezillon@free-electrons.com> References: <1459352394-22810-1-git-send-email-boris.brezillon@free-electrons.com> Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP sg_alloc_table_from_buf() provides an easy solution to create an sg_table from a virtual address pointer. This function takes care of dealing with vmallocated buffers, buffer alignment, or DMA engine limitations (maximum DMA transfer size). Signed-off-by: Boris Brezillon --- include/linux/scatterlist.h | 24 +++++++ lib/scatterlist.c | 161 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 185 insertions(+) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 556ec1e..4a75362 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -41,6 +41,27 @@ struct sg_table { unsigned int orig_nents; /* original size of list */ }; +/** + * struct sg_constraints - SG constraints structure + * + * @max_chunk_len: maximum chunk buffer length. Each SG entry has to be smaller + * than this value. Zero means no constraint. + * @required_alignment: minimum alignment. Is used for both size and pointer + * alignment. If this constraint is not met, the function + * should return -EINVAL. + * @preferred_alignment: preferred alignment. Mainly used to optimize + * throughput when the DMA engine performs better when + * doing aligned accesses. + * + * This structure is here to help sg_alloc_table_from_buf() create the optimal + * SG list based on DMA engine constraints. + */ +struct sg_constraints { + size_t max_chunk_len; + size_t required_alignment; + size_t preferred_alignment; +}; + /* * Notes on SG table design. * @@ -265,6 +286,9 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages, unsigned int n_pages, unsigned long offset, unsigned long size, gfp_t gfp_mask); +int sg_alloc_table_from_buf(struct sg_table *sgt, const void *buf, size_t len, + const struct sg_constraints *constraints, + gfp_t gfp_mask); size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, size_t buflen, off_t skip, bool to_buffer); diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 004fc70..94776ff 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -433,6 +433,167 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, } EXPORT_SYMBOL(sg_alloc_table_from_pages); +static size_t sg_buf_chunk_len(const void *buf, size_t len, + const struct sg_constraints *cons) +{ + size_t chunk_len = len; + + if (cons->max_chunk_len) + chunk_len = min_t(size_t, chunk_len, cons->max_chunk_len); + + if (is_vmalloc_addr(buf)) { + unsigned long offset_in_page = offset_in_page(buf); + size_t contig_len = PAGE_SIZE - offset_in_page; + unsigned long phys = vmalloc_to_pfn(buf) - offset_in_page; + const void *contig_ptr = buf + contig_len; + + /* + * Vmalloced buffer might be composed of several physically + * contiguous pages. Avoid extra scattergather entries in + * this case. + */ + while (contig_len < chunk_len) { + if (phys + PAGE_SIZE != vmalloc_to_pfn(contig_ptr)) + break; + + contig_len += PAGE_SIZE; + contig_ptr += PAGE_SIZE; + phys += PAGE_SIZE; + } + + chunk_len = min_t(size_t, chunk_len, contig_len); + } + + if (!IS_ALIGNED((unsigned long)buf, cons->preferred_alignment)) { + const void *aligned_buf = PTR_ALIGN(buf, + cons->preferred_alignment); + size_t unaligned_len = (unsigned long)(aligned_buf - buf); + + chunk_len = min_t(size_t, chunk_len, unaligned_len); + } else if (chunk_len > cons->preferred_alignment) { + chunk_len &= ~(cons->preferred_alignment - 1); + } + + return chunk_len; +} + +#define sg_for_each_chunk_in_buf(buf, len, chunk_len, constraints) \ + for (chunk_len = sg_buf_chunk_len(buf, len, constraints); \ + len; \ + len -= chunk_len, buf += chunk_len, \ + chunk_len = sg_buf_chunk_len(buf, len, constraints)) + +static int sg_check_constraints(struct sg_constraints *cons, + const void *buf, size_t len) +{ + if (!cons->required_alignment) + cons->required_alignment = 1; + + if (!cons->preferred_alignment) + cons->preferred_alignment = cons->required_alignment; + + /* Test if buf and len are properly aligned. */ + if (!IS_ALIGNED((unsigned long)buf, cons->required_alignment) || + !IS_ALIGNED(len, cons->required_alignment)) + return -EINVAL; + + /* + * if the buffer has been vmallocated and required_alignment is + * more than PAGE_SIZE we cannot guarantee it. + */ + if (is_vmalloc_addr(buf) && cons->required_alignment > PAGE_SIZE) + return -EINVAL; + + /* + * max_chunk_len has to be aligned to required_alignment to + * guarantee that all buffer chunks are aligned correctly. + */ + if (!IS_ALIGNED(cons->max_chunk_len, cons->required_alignment)) + return -EINVAL; + + /* + * preferred_alignment has to be aligned to required_alignment + * to avoid misalignment of buffer chunks. + */ + if (!IS_ALIGNED(cons->preferred_alignment, cons->required_alignment)) + return -EINVAL; + + return 0; +} + +/** + * sg_alloc_table_from_buf - create an SG table from a buffer + * + * @sgt: SG table + * @buf: buffer you want to create this SG table from + * @len: length of buf + * @constraints: optional constraints to take into account when creating + * the SG table. Can be NULL if no specific constraints are + * required. + * @gfp_mask: type of allocation to use when creating the table + * + * This function creates an SG table from a buffer, its length and some + * SG constraints. + * + * Note: This function supports vmallocated and physically contiguous buffers. + */ +int sg_alloc_table_from_buf(struct sg_table *sgt, const void *buf, size_t len, + const struct sg_constraints *constraints, + gfp_t gfp_mask) +{ + struct sg_constraints cons = { }; + size_t remaining, chunk_len; + const void *sg_buf; + int i, ret; + + if (constraints) + cons = *constraints; + + ret = sg_check_constraints(&cons, buf, len); + if (ret) + return ret; + + sg_buf = buf; + remaining = len; + i = 0; + sg_for_each_chunk_in_buf(sg_buf, remaining, chunk_len, &cons) + i++; + + ret = sg_alloc_table(sgt, i, gfp_mask); + if (ret) + return ret; + + sg_buf = buf; + remaining = len; + i = 0; + sg_for_each_chunk_in_buf(sg_buf, remaining, chunk_len, &cons) { + if (is_vmalloc_addr(sg_buf)) { + struct page *vm_page; + + vm_page = vmalloc_to_page(sg_buf); + if (!vm_page) { + ret = -ENOMEM; + goto err_free_table; + } + + sg_set_page(&sgt->sgl[i], vm_page, chunk_len, + offset_in_page(sg_buf)); + } else { + sg_set_buf(&sgt->sgl[i], sg_buf, chunk_len); + } + + i++; + } + + return 0; + +err_free_table: + sg_free_table(sgt); + + return ret; +} +EXPORT_SYMBOL(sg_alloc_table_from_buf); + void __sg_page_iter_start(struct sg_page_iter *piter, struct scatterlist *sglist, unsigned int nents, unsigned long pgoffset)