[PATCH 1/3] b43: replace DMA translation workarounds with just a one, commented

[Rafał Miłecki]

On Jul 20, 2011 10:55 AM, "Michael Büsch" <m at bues.ch> wrote:
>
> On Wed, 20 Jul 2011 08:16:08 +0200
> Rafał Miłecki <zajec5 at gmail.com> wrote:
>
> > W dniu 20 lipca 2011 01:15 użytkownik Michael Büsch <m at bues.ch> napisał:
> > > On Wed, 20 Jul 2011 00:12:20 +0200
> > > Rafał Miłecki <zajec5 at gmail.com> wrote:
> > >> +              * be fixed on ssb side, but requires testing with b43,
> > >> +              * b43legacy and b44. */
> > >
> > > No it doesn't. b44 and b43legacy don't use 64bit DMA.
> > > Just fix it in ssb, please.
> >
> > They (drivers) don't, but what if we start giving them routing for
> > 64-bit DMA? AFAIU they treat 64-bit DMA as 32-bit one (according to
> > specs: "If 64 Bit isn't an option, Silicon Backplane and PCI-E buses
> > can use 32 bit DMA.").
> >
> > Won't they start using 64-bit DMA in the 32-bit way but with 64-bit
> > routing bits?
> >
>
> I have no idea what you're talking about.
> The fact is: These "temporary workarounds" tend to stay in the driver forever
> if we don't fix it _now_. So please fix it now.
> We know whether we are on 64bit DMA or not. So if we are on 64bit DMA, use the 64bit mask.
> Simply pass the "32 or 64 bit" boolean flag to ssb_dma_translation() as parameter.
> There's nothing that can go wrong here with older drivers.

Sorry, for not explaining this well eno
ugh. I'm afraid of situation where b44 driver supports 64-bit DMA
device *without* handling this as such a device. It treats it as
32-bit one and it works thanks to kind of ssb's fallback described in
the specs. Now if I clean ssb_dma_translation we will detect that DMA
is 64-bit and we will pass different routing bit.

So as the result b44 will still treat DMA as 32-bit one, but it will
start using routing for 64-bit one.
Alternative is to do not detect kind of DMA in the ssb_dma_translation
but take it as a parameter (as you suggested). A *little* more to care
about on the driver side but would make a trick.

Or... is there any b44 supported device with 64-bit DMA at all?


-- 
Rafał