Re: [PATCH RFC] x86: Fix 64-bit DMA masks on VIA

[Alan Cox]

On Thu, 24 Apr 2008 16:06:00 +0200
Michael Buesch <mb@xxxxxxxxx> wrote:

> On Thursday 24 April 2008 15:43:50 Andi Kleen wrote:
> > Michael Buesch <mb@xxxxxxxxx> writes:
> > 
> > > This untested patch is supposed to fix DMAing on some VIA boards.
> > > Currently the DMA subsystem returns an error, if the driver does
> > > tell that it supports a 64bit DMA mask. So the driver probing
> > > would fail in that case. 
> > 
> > The driver is broken then. It is supposed to retry with a small
> > mask on an error. Please fix the driver.
> 
> I already added a workaround to the driver.
> Why do we need to workaround this in _every_ driver? (Note that _every_
> driver supporting a 64bit mask is affected). Why not fix it in the DMA layer?

Some hardware wants to know it can get a given DMA mask or failure. I
agree however that a "pci_prefer_64bit_dma(pdev)" function would be a
good patch for someone to submit tot he PCI layer code.

Alan
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