Messages in this thread | | | From | "James Gurganus" <> | Subject | Serial Driver IRQ Sharing with Non-Serial Devices | Date | Thu, 30 Sep 1999 23:19:30 -0700 |
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Hi Folks,
Hoping someone here can help me with a problem regarding the serial driver sharing an IRQ with a non-serial driver. Some one please guide me gently to a better place if this is the wrong forum for this question. :)
I have an Intel i810 based motherboard with a single PCI slot, on-board 82557+ Ethernet, and on-board ES1373 sound. In the PCI slot is an ActionTec PCI modem with built-in controller (i.e., _not_ a win-modem). Unfortunately, the ES1371 sound and PCI slot (modem) share PCI INT A which is routed to IRQ 11.
In this configuration with both the sound driver and serial driver sharing IRQ 11, sound works but the modem doesn't (e.g., no response in minicom). If I disable the sound driver (rmmod es1371), the modem works fine.
We've tested the problem with Linux 2.2.12 and many revisions of 2.3.X up to and including 2.3.18ac10.
Other testing we have done: 1) On a similar i810-based motherboard with more slots, I have arranged an IRQ conflict between the ethernet driver and the serial driver. In this case, the ethernet driver works (mostly) but the modem does not. This seems to help point guiltiness at the serial driver. 2) On the single slot i810 board, if I physically wire the ES1373 interrupt line to the interrupt (PCI INT C) of the Ethernet (in effect, wire-ORing them) AND force the es1371 driver to use the IRQ for INT C (in this case, IRQ 5), all three components work fine. The ethernet and sound drivers successfully share IRQ 5 and the modem is happy with its independent IRQ. This again seems to point to the serial driver as the culprit.
Of course, our hacked blue-wire solution isn't too great (to say the least). Plus, Win98 seems to successfully share the serial device with the sound making the local Linux guys/gals look bad :-), but also this helps give confidence that the hardware is okay.
So finally the questions:
1) Is there a limitation with the serial driver with respect to interrupt sharing? Some folks have suggested that the serial driver can only share interrupts with serial devices and not with non-serial devices. 2) If the answer to 1 is "yes, there is a limitation", is anybody looking into a fix/improvement? If so, any guesses on the availability? 3) If the serial driver IS capable, any ideas of what else could be wrong?
Thanks very much for any help!
-- James Gurganus (james@gurganus.net)
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