From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:46822 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758892Ab2JKVaz (ORCPT ); Thu, 11 Oct 2012 17:30:55 -0400 From: Laurent Pinchart To: Tomasz Stanislawski Cc: linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, airlied@redhat.com, m.szyprowski@samsung.com, kyungmin.park@samsung.com, sumit.semwal@ti.com, daeinki@gmail.com, daniel.vetter@ffwll.ch, robdclark@gmail.com, pawel@osciak.com, linaro-mm-sig@lists.linaro.org, hverkuil@xs4all.nl, remi@remlab.net, subashrp@gmail.com, mchehab@redhat.com, zhangfei.gao@gmail.com, s.nawrocki@samsung.com, k.debski@samsung.com Subject: Re: [PATCHv10 23/26] v4l: vb2-dma-contig: align buffer size to PAGE_SIZE Date: Thu, 11 Oct 2012 23:31:39 +0200 Message-ID: <11844448.MZrezqZD1L@avalon> In-Reply-To: <1349880405-26049-24-git-send-email-t.stanislaws@samsung.com> References: <1349880405-26049-1-git-send-email-t.stanislaws@samsung.com> <1349880405-26049-24-git-send-email-t.stanislaws@samsung.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Tomasz, On Wednesday 10 October 2012 16:46:42 Tomasz Stanislawski wrote: > Most operations on DMA and DMABUF framework need page > aligned buffers. The comment is a bit misleading, the buffer is already page-aligned (unless I'm mistaken dma_alloc_coherent() returns a page-aligned buffer) but its size isn't a multiple of the page size. Do we really need a page size multiple ? Isn't it enough to make the size a multiple of the cache line size ? > This fix guarantees this requirement > for vb2-dma-contig buffers. > > Signed-off-by: Tomasz Stanislawski > --- > drivers/media/v4l2-core/videobuf2-dma-contig.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c > b/drivers/media/v4l2-core/videobuf2-dma-contig.c index 571a919..002ee50 > 100644 > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c > @@ -162,6 +162,9 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned long > size) if (!buf) > return ERR_PTR(-ENOMEM); > > + /* align image size to PAGE_SIZE */ > + size = PAGE_ALIGN(size); > + > buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr, GFP_KERNEL); > if (!buf->vaddr) { > dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size); -- Regards, Laurent Pinchart