From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by oss.sgi.com id ; Wed, 5 Jul 2000 18:25:35 -0700 Received: from u-69.karlsruhe.ipdial.viaginterkom.de ([62.180.21.69]:28932 "EHLO u-69.karlsruhe.ipdial.viaginterkom.de") by oss.sgi.com with ESMTP id ; Wed, 5 Jul 2000 18:25:33 -0700 Received: by lappi.waldorf-gmbh.de id ; Wed, 5 Jul 2000 18:25:10 -0700 Date: Thu, 6 Jul 2000 03:25:10 +0200 From: Ralf Baechle To: Erik Niessen Cc: linux-mips@oss.sgi.com Subject: Re: Doing DMA with the ide-driver Message-ID: <20000706032510.A5122@bacchus.dhis.org> References: <20000706002824.64367.qmail@hotmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0.1i In-Reply-To: <20000706002824.64367.qmail@hotmail.com>; from erik_niessen@hotmail.com on Thu, Jul 06, 2000 at 02:28:24AM +0200 X-Accept-Language: de,en,fr Sender: owner-linux-mips@oss.sgi.com Precedence: bulk Return-Path: X-Orcpt: rfc822;linux-mips-outgoing On Thu, Jul 06, 2000 at 02:28:24AM +0200, Erik Niessen wrote: > I am trying to get an external ide-pci controller (CMD 646) working on an > embedded mips board. The kernel-source is based on a 2.2.12 source tree. > > The problem is doing DMA. I receive address (0x80ff0000) for my dmatable in > the function ide_setup_dma (__get_free_pages). Then in ide_buildtable it > sets up the dmatable. Address 0x80376000 and a count of 0x400 > (check_partition reads 2 sectors from the harddrive). These are all virtual > addresses. For setting up the dmatable I use physical addresses. On the > embedded board there is a 1:1 map of i/o bus to main memory so > platform_mem_iobus_base is 0. > > So after doing the DMA read, I read only zero's at address 0x80376000 and > the kernel hangs. But the harddrive is ready and I can't find any errors. It > seems that it writes the data to a different memory location. After > searching the memory the data is written at address 0x80000000?? Is the > memory manager somewhere in between??? > > The next thing I did was reserving a piece of physical memory for DMA and > fill in the dmatable myself. So that it uses my piece of reserved memory. > After I did this, the data was at the correct address and the kernel didn't > crash. Is this the solution??? What you're observing can be explained by caches not being flushed properly. What kernel versions are you using? Ralf