Message-ID: <459A88F1.70706@s5r6.in-berlin.de>
Date:	Tue, 02 Jan 2007 17:31:45 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
CC:	Kyuma Ohta <whatisthis@...m.home.ne.jp>,
	Andreas Schwab <schwab@...e.de>, linux-kernel@...r.kernel.org,
	Linux1394-devel ML <linux1394-devel@...ts.sourceforge.net>
Subject: Re: 2.6.20-rc2: kernel BUG at include/asm/dma-mapping.h:110!

(list address corrected, and a question added...)

On 1/2/2007 4:53 PM, I wrote:
> Kyuma Ohta wrote:
> ...
>> Now,I'm testing 2.6.20-rc3 for x86_64, submitted patch for this issue;
>> "Fault has happened  in 'cleanuped' sbp2/1394 module in *not 32bit*
>> architecture hardwares ."
>> 
>> As result of, sbp2 driver in 2.6.20-rc3 is seems to running 
>> w/o any faults,but communication both host and harddrive(s) 
>> was seems to be unstable yet :-(
>> Sometimes confuse packets,such as *very* older 1394 driver :-(
> 
> That is, sbp2 on 2.6.20-rc3 works less stable for you than on 2.6.19? Or
> which previous kernel is the basis of your comparison? Are there any log
> messages or other diagnostics? And what hardware do you have?
> 
> If you can tell which kernel was good for you, I could create a set of
> patches for you which allows to revert sbp2 while keeping the rest of
> the kernel at the level of 2.6.20-rc3, so that you could find the
> destabilizing change (if it happened in sbp2, not somewhere else).
> 
> Although there was a certain volume of changes to sbp2 between 2.6.19
> and 2.6.20-rc{1,3}, none of them should change the behavior except for:
> 
>  - commit 0b885449ac6fab42cd6808c9ea8d6e456e0e65b7 "ieee1394: sbp2:
>    remove duplicate code" modifying the extremely unlikely case that
>    a bus reset occurs right after completion status of an unsuccessfully
>    completed command came in,
> 
>  - commit 23077f1d72d279244536f11db51258fc4759c81a "ieee1394: sbp2:
>    slightly reorder sbp2scsi_abort" which improves a SCSI error handler,
>    mostly relevant if a command timed out.
> 
>  - commit b2bb550c4a10c44e99fe469cfaee81e2e3109994 "ieee1394: sbp2: pass
>    REQUEST_SENSE through to the target" which exposes targets to a SCSI
>    command which was previously blocked out. But this command is either
>    never issued by stock Linux SCSI drivers to SBP-2 targets anyway
>    because they provide autosense data, or has to be be properly
>    supported by SBP-2 targets if targets don't send autosense data.
>    (This is also about error handling, unless special application
>    software is explicitly generating this command.)
> 
> The DMA mapping patch did only change behavior because it was just
> faulty. After its correction in 2.6.20-rc3, it really is a trivial 1:1
> conversion from the pci_dma_ API to the generic dma_ API. I neither
> added nor removed anything from the mapping operations and they should
> behave exactly the same as before with PCI FireWire controllers.
> 
> Or could there have been some hidden mistake in sbp2's old pci_dma_
> usage which now turns into real problems after 1:1 conversion to the
> dma_API?
> 
> Or are there any DMA related properties of hardware that the DMA mapping
> infrastructure cannot figure out from the generic device (contained in a
> pci_device) compared to the pci_device?

Or are there some restrictions implicit in mappings via pci_dma_ API
which are lifted when using mappings via dma_ API?
-- 
Stefan Richter
-=====-=-=== ---= ---=-
http://arcgraph.de/sr/
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