Messages in this thread | | | Date | Thu, 02 Mar 2006 18:05:16 -0800 | From | Frithjof Kruggel <> | Subject | Bug in aic79xx_osm.c: synchronous mode not negotiated |
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Hi,
I have an HP tape library attached to an Adaptec 29320A Ultra320 SCSI card. While upgrading the kernel from version 2.6.13.5 to 2.6.15.5, I found that writing tapes slowed down from 24 MB/s to 4.5 MB/s.
Switching on debug mode in the driver revealed that for both the tape drive and the autochanger, asynchronous mode is negotiated with the new kernel.
After playing around with the code, I found that there is a problem with function ahd_send_async() in file aic79xx_osm.c.
Reverting a piece of code in this function back to version 2.6.13.5 solved the problem (specifically, replacing lines 1609-1632 of aic79xx_osm.c in version 2.6.15.5 with lines 4240-4263 in version 2.6.13.5). Synchronous mode is now negiotiated for both targets.
Of course, I have no idea about any potential side effects of this change, so I would rather give this problem back to the maintainers of this code. Feel free to contact me if you need more information. Please, cc: to the address above, as I am not a regular subscriber to this list.
Best wishes,
Frithjof Kruggel
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