Subject: Re: bus_dmamap_ limitation
To: mike varga <firstname.lastname@example.org>
From: Jaromir Dolecek <email@example.com>
Date: 04/03/2002 21:28:43
Note that ISA DMA is limited to lower 16 MB of memory (use 24bit address),
countrary to PCI DMA, which use either 32bit or 64bit addresses.
If your driver attaches before ISA drivers and uses all the memory
in first 16MB, ISA drivers won't be able to get DMA memory.
mike varga wrote:
> Yes, but I did solve the problem.
> It turns out that the isadma
> driver which attaches after
> my driver has a problem with
> allocating dma buffers within
> some region of memory. It is
> forced to allocate above
> what it typically does because
> of what I require.
> I am not sure what that is, and
> I am not concerned since I do
> not need it, although the floppy
> drive does not work anymore.
> An interrested party may
> try looking at the parameters
> that are passed into the various
> bus_dmamem and bus_dmamap
> ----- Original Message -----
> From: "Jaromir Dolecek" <firstname.lastname@example.org>
> To: "mike varga" <email@example.com>
> Cc: <firstname.lastname@example.org>
> Sent: Tuesday, April 02, 2002 1:08 PM
> Subject: Re: bus_dmamap_ limitation
> > mike varga wrote:
> > > I found that when I allocate
> > > more than 1000, other drivers
> > > will not attach successfully.
> > Are you absolutely positive you need such a huge number of buffers
> > for DMA?
> > Jaromir
> > --
> > Jaromir Dolecek <jdolecek@NetBSD.org>
> > -=- We should be mindful of the potential goal, but as the tantric -=-
> > -=- Buddhist masters say, ``You may notice during meditation that you -=-
> > -=- sometimes levitate or glow. Do not let this distract you.'' -=-
Jaromir Dolecek <jdolecek@NetBSD.org> http://www.NetBSD.org/Ports/i386/ps2.html
-=- We should be mindful of the potential goal, but as the tantric -=-
-=- Buddhist masters say, ``You may notice during meditation that you -=-
-=- sometimes levitate or glow. Do not let this distract you.'' -=-