Re: Feral ISP driver: dma map request problem
On Friday 09 January 2004 11:06 am, Kelledin wrote:
> Hmm. It looks like the driver tried to do mapping as if the
> machine had a 32-bit address space. IIRC what it's supposed
> to do is when it grabs some memory for PCI DMA mapping, it's
> supposed to pass a flag signifying that the DMA region should
> be accessible via 32-bit physical addressing. Otherwise PCI
> devices would likely have some trouble getting to it!
> Apparently that flag didn't get passed somewhere, and the
> prospective DMA buffer got allocated way high in the 64-bit
> address space. So it couldn't be set up as a DMA buffer, and
> the kernel's PCI DMA mapper spit it back. By my
> understanding, that's a fairly common mistake when porting
> kernel drivers to 64-bit architectures.
> I'll take a look at the source code this afternoon and see
> what I can spot.
Apparently this type of DMA mapping doesn't work quite like I
thought it did, or I'm missing something somewhere.
Also, I'm compelled to wonder...what's your system type? Some
revisions of the EB164 series core-logic have some limitations
as to available DMA methods. You might be hitting one of those
"If a server crashes in a server farm and no one pings it, does
it still cost four figures to fix?"