From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753294Ab0JMHyW (ORCPT ); Wed, 13 Oct 2010 03:54:22 -0400 Received: from h5.dl5rb.org.uk ([81.2.74.5]:56778 "EHLO h5.dl5rb.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753275Ab0JMHyV (ORCPT ); Wed, 13 Oct 2010 03:54:21 -0400 Date: Wed, 13 Oct 2010 08:53:47 +0100 From: Ralf Baechle To: Kevin Cernekee Cc: dediao@cisco.com, ddaney@caviumnetworks.com, dvomlehn@cisco.com, sshtylyov@mvista.com, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/2] MIPS: HIGHMEM DMA on noncoherent MIPS32 processors Message-ID: <20101013075346.GA24052@linux-mips.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 09, 2010 at 06:53:42PM -0700, Kevin Cernekee wrote: > [v3: Patch has been rebased against linux-queue.git, which uses the new > dma-mapping-common.h API.] > > The MIPS DMA coherency functions do not work properly (i.e. kernel oops) > when HIGHMEM pages are passed in as arguments. This patch uses the PPC > approach of calling kmap_atomic() with IRQs disabled to temporarily map > high pages, in order to flush them out to memory. It's this disabling of interrupts which I don't like. It's easy to get around it by having one kmap type for each of process, softirq and interrupt context. The good news is that Peter Zijlstra has rewritten kmap to make the need for manually allocated kmap types go away and his patches are queued to be merged for 2.6.37. So I'd like to put this patch on hold until after his patches are merged. Does your system have both highmem and cache aliases? Ralf