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From: Bernhard Kaindl <bk@suse.de>
To: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: remote debugging via FireWire * __fast__ firedump!
Date: Thu, 6 Dec 2007 17:32:19 +0100 (CET)	[thread overview]
Message-ID: <alpine.LNX.0.9999-openSUSE-1.0712061713560.21849@jbgna.fhfr.qr> (raw)
In-Reply-To: <4755D186.20204@s5r6.in-berlin.de>

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

  parent reply	other threads:[~2007-12-06 16:32 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-10 11:42 What will be in the x86-64/x86 2.6.21 merge Andi Kleen
2007-02-10 13:43 ` [discuss] " Muli Ben-Yehuda
2007-02-10 13:52   ` Andi Kleen
2007-02-10 13:56     ` Muli Ben-Yehuda
2007-02-10 14:03       ` Andi Kleen
2007-02-10 13:51 ` remote debugging via FireWire (was What will be in the x86-64/x86 2.6.21 merge) Stefan Richter
2007-02-10 14:02   ` Andi Kleen
2007-02-10 15:14     ` remote debugging via FireWire Stefan Richter
2007-02-10 15:41       ` Andi Kleen
2007-02-10 19:16         ` Stefan Richter
2007-02-11 21:35           ` Benjamin Herrenschmidt
2007-02-12  6:49             ` Andi Kleen
2007-02-12  7:29               ` Benjamin Herrenschmidt
2007-12-04  3:45   ` remote debugging via FireWire * __fast__ firedump! Bernhard Kaindl
2007-12-04  7:39     ` Andi Kleen
2007-12-06 16:02       ` Bernhard Kaindl
2007-12-04 22:15     ` Stefan Richter
2007-12-04 22:34       ` Stefan Richter
2007-12-04 22:40         ` Stefan Richter
2007-12-06 18:36           ` [feedback discussion] Early boot debugging via FireWire (ohci1394_dma=early) Bernhard Kaindl
2007-12-06 19:23             ` Stefan Richter
2007-12-06 19:23             ` [PATCH] " Bernhard Kaindl
2007-12-06 20:23               ` Stefan Richter
2007-12-17 13:49               ` Ingo Molnar
2007-12-06 16:32       ` Bernhard Kaindl [this message]
2007-02-12 14:11 ` What will be in the x86-64/x86 2.6.21 merge James Morris
2007-02-12 14:14   ` Andi Kleen
2007-02-12 14:46     ` James Morris
2007-02-14  6:53     ` Rusty Russell

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