From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nils Faerber Subject: SATA DVD issue... Date: Mon, 09 Aug 2010 16:22:07 +0200 Message-ID: <4C600F0F.2010102@kernelconcepts.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: Received: from mail.kernelconcepts.de ([212.60.202.196]:43383 "EHLO mail.kernelconcepts.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756710Ab0HIOlO (ORCPT ); Mon, 9 Aug 2010 10:41:14 -0400 Received: from [192.168.2.151] by mail.kernelconcepts.de with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.69) (envelope-from ) id 1OiTJI-00050n-4d for linux-ide@vger.kernel.org; Mon, 09 Aug 2010 16:26:40 +0200 Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: linux-ide@vger.kernel.org Hello! I am trying to use a SATA DVD burner on a Marvell Kirkwood based platform, kernel is currently based on vanilla 2.6.34 with only board specific patches. SATA in general works just fine with harddisks. But when I attach my DVD drive any data read or write access triggers a BUG() in libata-sff.c: ata_bmdma_qc_issue(): ... /* see ata_dma_blacklisted() */ BUG_ON((ap->flags & ATA_FLAG_PIO_POLLING) && qc->tf.protocol == ATAPI_PROT_DMA); ... Command access (e.g. to eject the media or to erase a R/W disc) do work. My knowledge about ATA and SATA is quite limited so I cannot really interpret this issue. After some looking around and with the hint in the comment I tried blacklisting my drive, so I added an entry to libata-core.c: { "HL-DT-ST DVDRAM GH22LS50", "TL01", ATA_HORKAGE_NODMA }, Now the drive works but it is awefully slow - reading just a little over 1MB/s - well, without DMA mode this is quite expectable. I suspect that the Marvell SATA host driver should be OK and is not in fault - it is widely used in PCI setups and the SOC variant does almost not differ. And I also suspect that the above "fix" is not the best way to do it. I also tried the same driver with a USB-SATA connector (I do not have a SATA PC at hand right now) and there it behaves pretty normal with 5 to 10 times higher read rates. I would be more than happy if someone could help me diagnosing and especially fixing this problem. If I can give more information or try different things on the board just let know! Many thanks in advance! Cheers nils -- kernel concepts GbR Tel: +49-271-771091-12 Sieghuetter Hauptweg 48 Fax: +49-271-771091-19 D-57072 Siegen Mob: +49-176-21024535 http://www.kernelconcepts.de