>Number:         164651
>Category:       kern
>Synopsis:       Disabling DMA in new Freebsd 9.0 CAM drivers does not work
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jan 31 00:50:10 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Russell J. Yount
>Release:        Freebsd 9.0
>Organization:
Individual
>Environment:
FreeBSD server8.localdomain 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Sun Jan 15 
03:16:02 EST 2012     
[email protected]:/ufs/disk1/kernel/9.0/usr/src/sys/i386/compile/NET4801
  i386

FreeBSD server10.localdomain 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Sat Jan 21 
18:44:20 EST 2012     
[email protected]:/ufs/disk1/kernel/9.0/usr/src/sys/i386/compile/NET4801-NOCAM
  i386

>Description:
Soekris Engineering produced a number of early version of the net4801 that did 
not support DMA on Compact flash disks correctly. Compact flash cards that did 
support DMA would fail unless "hw.ata.ata_dma=0" was place in /boot/loader.conf
to disable DMA transfers for the ad driver.

FreeBSD 9.0 when compiled with CAM support appears not to disable DMA and just 
hanges with disk light on. When CAM support is not compiled in FreeBSD 9.0 
everything works as before.

The CAM subsystem appears not to support disabling DMA.

I have both net4801s that do and do not support DMA for Compact Flash Disks. 
The ones that support DMA do work correctly in FreeBSD 9.0. The problem 
described only affects early production models which did not support DMA.



  
>How-To-Repeat:
Using an old net4801 which does support DMA with a flash card that does.

I suspect DMA is not being disabled at all with CAM and could be tested with 
other disks.

Am willing to test fixes if needed.  
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted:
_______________________________________________
[email protected] mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-bugs
To unsubscribe, send any mail to "[email protected]"

Reply via email to