Messages in this thread | | | From | "Kathy Frazier" <> | Subject | RE: Problems related to DMA or DDR memory on Intel 845 chipset? | Date | Mon, 28 Jul 2003 16:56:42 -0500 |
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Mark,
>> then "hang". I had discovered that upon this failure, the logic analyzer >> shows that our device is asserting the interrupt. However, I also found (by >> adding my own debug to the kernel) that the 8259 Programmable Interrupt >> Controller never received the interrupt (it's bit was not set in the
>OK, so the problem is strictly on the PCI bus, between your device >and the PIC (or apic?)
That would appear to be the case. But as I said, it appears to be a nasty side affect from something that has gone wrong during a DMA transfer. BTW, we are using PIC
>> interrupt on the device). At this point of failure, no other IRQs are >> getting through, so the system appears to be completely hard hung even >> though various software components are still running. We are operating in a
>so why do you think this is a software problem?
I made this posting to see if anyone else has had problems with this hardware or to see if there were any known issues similar to what I've found.
>> employs the DDR memory technology) running Linux 2.4.20-8. Further testing >> has shown that "not receiving an interrupt" is just a nasty side affect from >> something that has gone wrong during a DMA transfer by our device. This was >> discovered when I changed the driver to poll for a DMA completion rather >> than have it interrupt me. Our system still hung. We are have tried
>that one mystifies me: how do you conclude the problem is a broken >DMA transfer if, when you convert to polling, the problem remains?
Why? The device is _still_ a DMA device. In this particular test I told it to initiate the DMA, but I did not enable it's ability to interrupt me when it was finished with the DMA. I poll to watch for it's completion.
>my conclusion would be that your device has somehow managed to lock >up the PIC's state-machine, or is somehow playing nasty with the bus.
I haven't ruled that out.
. . . Meanwhile, I made another discovery on the internet that indicates that DMA is not supported with an ICH4 controller (which is what this system has) until Linux version 2.5.12 (we're using 2.4.20-8). See: http://64.143.3.64/downloads/drivers/845/perform/linux/udma.htm. I posted a question concerning this to linux-kernel. See thread: DMA not supported with Intel ICH4 I/O controller? Unfortunately, I have not received any response that supports or refutes this. Any thoughts?
Thanks, Kathy
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