Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753883AbaA0Rwi (ORCPT ); Mon, 27 Jan 2014 12:52:38 -0500 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:50115 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753622AbaA0Rwh (ORCPT ); Mon, 27 Jan 2014 12:52:37 -0500 Date: Mon, 27 Jan 2014 17:52:31 +0000 From: Russell King - ARM Linux To: Michal Simek Cc: Guennadi Liakhovetski , linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [Q] block / zynq: DMA bouncing Message-ID: <20140127175231.GU15937@n2100.arm.linux.org.uk> References: <20140127170230.GQ15937@n2100.arm.linux.org.uk> <52E69B4E.5010604@monstr.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52E69B4E.5010604@monstr.eu> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 27, 2014 at 06:45:50PM +0100, Michal Simek wrote: > Why 0x4000? IRC Linux for ARM is using space for any purpose. > Russell knows this much better than I. Probably because as the kernel is loaded at 0x8000, it will place the swapper page table at 0x4000, thus covering from 0x4000 upwards. Thus, the majority of your un-DMA-able memory will be kernel text or swapper page tables. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/