Messages in this thread | | | Date | Thu, 04 Mar 1999 14:19:01 +0100 | From | "Albrecht Dreß" <> | Subject | PCI Bus master crashes -- help please |
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Hi all,
I am currently writing a kernel driver for ver. 2.0.36, but I have some serious problems with PCI bus master dma mode. The "new" extension card is a HUNT ENGINEERING HECPCI1 CompactPCI (a motherboard for TI 'C40 DSP modules). It uses an AMCC S5933 "Matchmaker" PCI chip. In interrupt driven mode, everything works fine.
Using pci bus master dma mode, in some cases the data transfer simply hangs the _complete_ kernel, that is: no reaction to keyboard or any other input, no kernel message at all (e. g. oops, /var/log/messages), ... This behaviour is highly sensitive to things:
o the S5933 can be configured to request bus mastership only to transfer at least 4 longwords from memory to the pci device. In this mode, dma works fine, but if it can request the bus for a single longword, the kernel hangs as described above.
o In the opposite direction (pci to memory) the S5933 will request bus mastership for one longword, and the kernel hangs almost at once.
Furthermore, the setting of the PCI_LATENCY_TIMER register seems to influence how fast the system will crash (although I could not find a setting which does not produce any crashes).
Could anybody give me a hint what goes wrong? I am almost sure that the addresses used during dma are correct as the interrupt driven version works without problems. What about the PCI_LATENCY_TIMER? What value should be used here? Where to find some more info?
Thanks in advance, Albrecht.
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