Re: Why is AHA152X_CS !64BIT?

[James Bottomley <James.Bottomley@suse.de>]

On Tue, 2010-09-07 at 14:48 -0700, Randy Dunlap wrote:
> On 09/07/10 14:41, Randy Dunlap wrote:
> > On 09/07/10 14:12, Konrad Rzeszutek Wilk wrote:
> >> On Monday 30 August 2010 07:13:17 Boaz Harrosh wrote:
> >>> On 08/23/2010 10:59 PM, Jiri Slaby wrote:
> >>>> Hi,
> >>>>
> >>>> I see that the aha152x driver for pcmcia is marked as unsupported on
> >>>> 64bit. But I also see a patch [1] which removes the restriction based on
> >>>> user's testing in bugzilla [2].
> >>>>
> >>>> Is there a reason why it would have to be marked as !64BIT? I'm asking
> >>>> because there is an opensuse user with this card who updated to 64-bit
> >>>> distro and lost this driver thereafter.
> >>>>
> >>>> [1] http://kerneltrap.org/mailarchive/linux-scsi/2010/3/6/6832393
> >>>> [2] https://bugzilla.kernel.org/show_bug.cgi?id=14333
> >>>>
> >>>> thanks,
> >>>
> >>> If memory serves correctly, it might be that you need more then 4 Gbyte
> >>> of memory installed to exercise the bug, something about IO bouncing
> >>> addresses > 4G.
> >>
> >> If the machine is using SWIOTLB, then the bounce buffer would be activated. By 
> >> default if your machine has more than 4GB compiled under x86_64 the SWIOTLB 
> >> is turned on - but if you have an Intel/AMD IOMMU it gets turned off. Which 
> >> is OK as the Intel/AMD IOMMUs would handle the 4GB restricted devices. So as 
> >> long as the driver has pci_dma_mask_set.
> >>
> >> Looking at the git gui blame tool history, the reason that was added was 
> >> for 'allow drivers to be built non-modular'.
> > 
> > 023ae619 (Robert P. J. Day  2007-03-26 16:06:45 -0400 14) 	depends on !64BIT
> > 
> > That commit just removed the "depends on m" part:
> > 
> > -	depends on m && !64BIT
> > +	depends on !64BIT
> > 
> > 
> >> So, does this driver build if you make it non-modular?
> > 
> > It shouldn't since it still depends on !64BIT.
> > 
> > I expect someone thought or had evidence that the driver was not 64-bit clean.
> > 
> > Is the bitkeeper kernel repo still visible somewhere?
> > Looks like we would need to look at it for patch history that far back.
> > 
> 
> http://linux.bkbits.net:8080/linux-2.6/?PAGE=cset&REV=3fe0bc41KO89ooP68UcrHEMVVAfDnw
> 
> but it doesn't quite make sense to me.  Sure, no ISA on x86_64, but that does not
> mean no PCMCIA on x86_64.

Actually, the patch is this one:

http://permalink.gmane.org/gmane.linux.scsi/5835

The complaint is that the driver spews warnings on a 64 bit compile, so
it's likely not 64 bit clean.

James