[Linux-parport] IRQ storm from Express card parallel port

Martin Mokrejs mmokrejs at fold.natur.cuni.cz
Mon Jun 25 08:44:05 EDT 2012

Andre Puschmann wrote:
> Hi Martin,
> On 06/25/2012 12:10 PM, Martin Mokrejs wrote:
>> Hi Andre,
>>   I played with a card from another vendor based on MosChip. It was stated
>> in the manual one cannot use IRQ, only memory-mapped IO. When I did use ECP+DMA
>> my Linux locked up soon. I could print fine but to scan a page I need a lot of luck.
>> Well, I need a patch which you can find on this list to disable to "fix" which
>> disabled ECP on many systems, inadverently, and was still necessary for 3.2.5 kernel.
>> I am attaching them for your convenience.
>>   I was dreaming about http://www.usbgear.com/USBG-EX-LPT.html which is based
>> on Oxford chipset, hopefully working in IRQ mode as well.
> Well, I am not 100% certain but the card came with a driver CD and it
> contains a inf file for Windows which is copyright by Oxford Technology.
> So that might mean that my adapter has the Oxford chip. Is there any way
> to check without breaking the housing?

Try lspci and also dmesg after loading the proper driver.

>>   It probably not much helpful answer but that's all I could contribute, from my user
>> experience. Threads on HPLIP forums merely document that scanning does not work
>> over these adapters, mention some "soft" ECP mode used by HP printers/scanners
>> if I remember right. Lookup the archives of this list, I think2 I posted some
>> URLs while it was fresh in my memory. In the end I gave up.
> Mmh, do you think the ECP patches help fixing this IRQ issues?

I could get the card running in ECP at all. It was only in SPP mode without
the patch. If your card is running in ECP+DMA mode you don't need them probably.
Or just try and report back the difference. It is also helpful to know if the patches
break other systems.


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