From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753391Ab0DYQNO (ORCPT ); Sun, 25 Apr 2010 12:13:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11551 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752972Ab0DYQNM (ORCPT ); Sun, 25 Apr 2010 12:13:12 -0400 Message-ID: <4BD46A0E.8030705@redhat.com> Date: Sun, 25 Apr 2010 13:13:02 -0300 From: Mauro Carvalho Chehab User-Agent: Thunderbird 2.0.0.22 (X11/20090609) MIME-Version: 1.0 To: =?UTF-8?B?UmljaGFyZCBSw7ZqZm9ycw==?= CC: Linux Media Mailing List , Linux Kernel Mailing List , Douglas Schilling Landgraf , Samuel Ortiz , "Williams, Dan J" Subject: Re: [PATCH 1/2] media: Add timberdale video-in driver References: <1271435291.11641.45.camel@debian> <4BD45EB1.5020804@redhat.com> <4BD46753.9010807@pelagicore.com> In-Reply-To: <4BD46753.9010807@pelagicore.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Richard Röjfors wrote: > On 04/25/2010 05:24 PM, Mauro Carvalho Chehab wrote: >> Richard Röjfors wrote: >>> This patch adds the timberdale video-in driver. >>> >>> The video IP of timberdale delivers the video data via DMA. >>> The driver uses the DMA api to handle DMA transfers, and make use >>> of the V4L2 videobuffers to handle buffers against user space. >>> Due to some timing constraint it makes sense to do DMA into an >>> intermediate buffer and then copy the data to vmalloc:ed buffers. >>> >>> If available the driver uses an encoder to get/set the video standard >>> >>> Signed-off-by: Richard Röjfors >>> +#define TIMBLOGIW_DMA_BUFFER_SIZE (TIMBLOGIW_BYTES_PER_LINE * 576) >> >> ... >> >>> +static int __timblogiw_alloc_dma(struct timblogiw_fh *fh, struct >>> device *dev) >>> +{ >>> + dma_addr_t addr; >>> + int err, i, pos; >>> + int bytes_per_desc = TIMBLOGIW_LINES_PER_DESC * >>> + timblogiw_bytes_per_line(fh->cur_norm); >>> + >>> + fh->dma.cookie = -1; >>> + fh->dma.dev = dev; >>> + >>> + fh->dma.buf = kzalloc(TIMBLOGIW_DMA_BUFFER_SIZE, GFP_KERNEL); >>> + if (!fh->dma.buf) >>> + return -ENOMEM; >> >> >> Why do you need a fixed DMA buffer size? Just allocate the buffer size >> dynamically at >> buffer_prepare callback. >>> + videobuf_queue_vmalloc_init(&fh->vb_vidq,&timblogiw_video_qops, >>> + NULL,&fh->queue_lock, V4L2_BUF_TYPE_VIDEO_CAPTURE, >>> + V4L2_FIELD_NONE, sizeof(struct videobuf_buffer), fh); >> >> You should be using, instead, videobuf_dma_sg or videobuf_cont, >> instead of >> using videobuf-vmalloc. This way, you'll avoid double buffering. > > 1. dma_sg can not be used, the DMA engine requires the memory blocks to > be aligned on a factor of bytes per line, so 4K pages wouldn't work. > > 2. > I tried using videobuf-dma-contig, but got poor performance. I can not > really explain why, I though it's due to the fact that the contiguous > buffer is allocated coherent -> no caching. > I saw both gstreamer and mplayer perform very badly. > The frame grabber requires the DMA transfer for a frame beeing started > while the frame is decoded. When I tested using contigous buffers > gstreamer sometimes was that slow that it sometimes missed to have a > frame queued when a transfer was finished, so I got frame drops. Any > other ideas of the poor performance? otherwise I would like to go for > the double buffered solution. The better is to fix videobuf-dma_contig to better work on your hardware. It makes sense to add a flag to allow specifying if it should use coherent or non-coherent memory for the dma buffer alloc/free calls. -- Cheers, Mauro