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SubjectRe: unchecked_isa_dma and BusLogic SCSI controller
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.
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