From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <95c74034a4670cd53c6ca43a793b40d6@plan9.bell-labs.com> From: jmk@plan9.bell-labs.com To: 9fans@cse.psu.edu Subject: Re: [9fans] drawterm strangeness In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Tue, 24 Jun 2003 13:24:21 -0400 Topicbox-Message-UUID: d9da1972-eacb-11e9-9e20-41e7f4b1d025 On Tue Jun 24 09:46:25 EDT 2003, rminnich@lanl.gov wrote: > On Tue, 24 Jun 2003, andrey mirtchovski wrote: > > > i urge you to turn dma/rwm on. > > This seems like something that just "ought to be" on. Why would it not be? > > ron The reason it's not on by default is that the driver currently does not do any DMA configuration by itself. In order to set up a DMA mode, both the ATA controller and the drive have to be configured appropriately. Setting the drive is straightforward, but setting the ATA controller is chip-specific. Instead, the driver makes the assumption that if you enable DMA, you know that the BIOS has configured both the drive and the controller correctly and that is not always the case. Plus, there are combinations of drives and controllers and DMA modes which don't work correctly, so the driver errs on the side of safety by default. If you know it's OK, it's easy to put the enable in cpurc. I did do some work on restructuring the ATA driver to make some of this possible, but it is incomplete.