Re: Why is AHA152X_CS !64BIT?

[Jiri Slaby <jslaby@suse.cz>]

On 09/07/2010 11:48 PM, 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.

Hmm, the changelog says:
The warning I saw was actually for the PCMCIA aha152x driver.

which I think are compiler warnings. But I see only one emitted by the
compiler and it is in a debug print.

thanks,
-- 
js
suse labs