Date: Tue, 11 Apr 2000 21:44:10 -0700 From: Mike Smith <msmith@freebsd.org> To: Warner Losh <imp@village.org> Cc: freebsd-hackers@freebsd.org Subject: Re: PCI DMA Questions Message-ID: <200004120444.VAA00544@mass.cdrom.com> In-Reply-To: Your message of "Tue, 11 Apr 2000 21:57:35 MDT." <200004120357.VAA34787@harmony.village.org>
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>
> I'm debugging a hunk of PCI hardware that I have under NDA. It
> doesn't seem to be initiating DMA transfers. This may be a hardware
> problem, but before I go back to the vendor, I want to make sure that
> I'm doing the DMA initialization right. It was my understanding that
> DMA just happened on the PCI bus and nothing special was needed.
Make sure that the busmaster bit is set in the PCI command register:
/* force the busmaster enable bit on */
if (!(command & PCIM_CMD_BUSMASTEREN)) {
device_printf(dev, "busmaster bit not set, enabling\n");
command |= PCIM_CMD_BUSMASTEREN;
pci_write_config(dev, PCIR_COMMAND, command, 2);
}
> Here's what I'm doing in my attach routine. Most of this code was
> culled from ahc.c and friends.
Not to bounce too much, but you may find the examples in the amr and mlx
drivers easier to follow (maybe not, too). I forgot who I stole them
from though - probably Jonathan's ida code. This isn't your problem
though.
--
\\ Give a man a fish, and you feed him for a day. \\ Mike Smith
\\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org
\\ and he'll hate you for a lifetime. \\ msmith@cdrom.com
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