From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:47435 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750905Ab2GEQgS (ORCPT ); Thu, 5 Jul 2012 12:36:18 -0400 From: Laurent Pinchart To: Michael Jones Cc: linux-media ML Subject: Re: capture_mem limitations in OMAP ISP Date: Thu, 05 Jul 2012 18:36:24 +0200 Message-ID: <2278346.UGGOgjoZYS@avalon> In-Reply-To: <4FF2BF79.2020302@matrix-vision.de> References: <4FF2BF79.2020302@matrix-vision.de> 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 Michael, On Tuesday 03 July 2012 11:46:33 Michael Jones wrote: > Hi Laurent & co., > > I'm looking at the memory limitations in the omap3isp driver. 'struct > isp_video' contains member 'capture_mem', which is set separately for each > of our v4l2 video device nodes. The CCDC, for example, has capture_mem = > 4096 * 4096 * 3 = 48MB, while the previewer and resizer each have twice > that. Where do these numbers come from? That's mostly historical. When developing the driver for the N900 we set a limit to avoid putting too much pressure on the system memory, and 3x8MP buffers was considered to be enough. We could raise the limit, remove it completely, or implement a policy mechanism to let a privileged userspace application specify limits. The later might be interesting as a core V4L2 mechanism. > Is the CCDC incapable of DMA'ing more than 48MB into memory? I know that > ISP_VIDEO_MAX_BUFFERS also limits the # of buffers, but I assume this is > basically an arbitrary number so we can have a finite array of > isp_video_buffer's. The 48MB, on the other hand, looks like it might have a > good reason. -- Regards, Laurent Pinchart