Messages in this thread | | | Date | Thu, 6 Dec 2007 17:32:19 +0100 (CET) | From | Bernhard Kaindl <> | Subject | Re: remote debugging via FireWire * __fast__ firedump! |
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On Tue, 4 Dec 2007, Stefan Richter wrote: > > A quick note to this text from > http://www.suse.de/~bk/firewire/ohci1394_dma_early.diff : >> + As all changes to the FireWire bus such as enabling and disabling >> + devices cause a bus reset and thereby disable remote DMA for all >> + devices, be sure to have FireWire enabled on the debug host (and >> + the cable plugged) before booting the debug target for debugging. > > Bus resets are also caused by bus managing software, which Linux' old > and new FireWire stacks and the stacks of all other FireWire capable > desktop OSs are to varying degrees.
Yes, I can also trigger it raw1394_reset_bus() from libraw1394.
> I wonder if the following could > happen: The two PCs are directly connected, only the PHY of the > debugging PC is active, then the PHY of the debugged PC is activated, > becomes root node, debugging PC examines the bus, then resets the bus to > force its own PHY to become root node in order to get a working > isochronous resource manager. This bus reset would switch remote DMA on > the debugged PC off.
Yes, that's the case. The PHY of the debugging PC must be active before the booting a kernel with the early OHCI-1394 initialisation on the debugged machine.
I tried to to instruct users to do exactly that in that part of the help text, but changed the wording now in to hope to make it clearer:
+ [...] be sure to have the cable plugged and FireWire enabled on + the debugging host before booting the debug target for debugging.
and I added new file, installed as Documentation/debugging-via-ohci1394.txt to give a more detailed HOWTO with links to all available tools and a step by step guide on how to create a setup for using firescope.
ftp://ftp.suse.de/private/bk/firewire/kernel/ohci1394_dma_early-v2.diff
I'll submit that patch for full review in my next mail.
Bernhard
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