From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: unchecked_isa_dma and BusLogic SCSI controller Date: Thu, 2 Nov 2006 13:35:48 +0000 Message-ID: <20061102133548.GA27715@infradead.org> References: <20061101235330.GA30843@srv.junsun.net> <20061101173358.7b027d13.randy.dunlap@oracle.com> <20061102124128.GC31830@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from pentafluge.infradead.org ([213.146.154.40]:4226 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1752305AbWKBNg3 (ORCPT ); Thu, 2 Nov 2006 08:36:29 -0500 Content-Disposition: inline In-Reply-To: <20061102124128.GC31830@parisc-linux.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Matthew Wilcox Cc: Randy Dunlap , Jun Sun , linux-scsi@vger.kernel.org, lkml On Thu, Nov 02, 2006 at 05:41:28AM -0700, Matthew Wilcox wrote: > On Wed, Nov 01, 2006 at 05:33:58PM -0800, Randy Dunlap wrote: > > unchecked_isa_dma - 1=>only use bottom 16 MB of ram (ISA DMA addressing > > restriction), 0=>can use full 32 bit (or better) DMA > > address space > > > > > It is hard for me to see why BusLogic controller would only do DMA > > > in low 16MB. Is there a fix for this? > > > > Does anyone know that controller hardware and its limitations? > > I don't, but: > > if (pci_set_dma_mask(PCI_Device, DMA_32BIT_MASK )) > continue; > > So somebody thinks the device can do 32-bit addressing. I would expect > that setting unchecked_isa_dma is a historical mistake. However, I > don't have any cards of this type to test. The buslogic driver also supports non-PCI devices, and at least the ISA boards have the obvious limitiation that unchecked_isa_dma = 1 caters to. Now someone would have to audit the driver whether it's enough to only set this on the actual isa hosts instead of the host template.