DVD/CD lost after r246713

Hi,

When trying to update a i386 system from r245422 to r246923, the DVD/CD devices
cd0/cd1 could no more be attached.

Here is a relevant part of a verbose dmaeg:

pass0 at ata0 bus 0 scbus0 target 0 lun 0
pass0: <WDC WD3200AAJB-00J3A0 01.03E01> ATA-8 device
pass0: Serial Number WD-WCAV2F115406
pass0: 100.000MB/s transfers (UDMA5, PIO 8192bytes)
pass1 at ata0 bus 0 scbus0 target 1 lun 0
pass1: <WDC WD600BB-75CAA0 16.06V16> ATA-5 device
pass1: Serial Number WD-WMA8F2128712
pass1: 100.000MB/s transfers (UDMA5, PIO 8192bytes)
pass2 at ata1 bus 0 scbus1 target 0 lun 0
pass2: <SAMSUNG DVD-ROM SD-616T F310> Removable CD-ROM SCSI-0 device
pass2: 33.300MB/s transfers (UDMA2, ATAPI 12bytes, PIO 65534bytes)
pass3 at ata1 bus 0 scbus1 target 1 lun 0
pass3: <HL-DT-ST CD-RW GCE-8481B C102> Removable CD-ROM SCSI-0 device
pass3: 33.300MB/s transfers (UDMA2, ATAPI 12bytes, PIO 65534bytes)
TSC timecounter discards lower 1 bit(s)
Timecounter "TSC-low" frequency 1196040076 Hz quality 800
uhub0: 2 ports with 2 removable, self powered
uhub1: 2 ports with 2 removable, self powered
uhub2: 2 ports with 2 removable, self powered
GEOM: new disk cd0
GEOM: new disk cd1
GEOM: new disk ada0
GEOM: new disk ada1
uhub3: 6 ports with 6 removable, self powered
ugen0.2: <Logitech> at usbus0
ums0: <Logitech Optical USB Mouse, class 0/0, rev 2.00/3.40, addr 2> on usbus0
ums0: 3 buttons and [XYZ] coordinates ID=0
ata1: reset tp1 mask=03 ostat0=d0 ostat1=50
ata1: stat0=0x10 err=0x01 lsb=0x14 msb=0xeb
ata1: stat1=0x10 err=0x01 lsb=0x14 msb=0xeb
ata1: reset tp2 stat0=10 stat1=10 devices=0x30000
(cd0:ata1:0:0:0): got CAM status 0x50
(cd0:ata1:0:0:0): fatal error, failed to attach to device
(cd0:ata1:0:0:0): lost device, 4 refs
Opened disk cd0 -> 6
(cd0:ata1:0:0:0): removing device entryata1: reset tp1 mask=03 ostat0=50 ostat1=d0
ata1: stat0=0x10 err=0x01 lsb=0x14 msb=0xeb
ata1: stat1=0x10 err=0x01 lsb=0x14 msb=0xeb
ata1: reset tp2 stat0=10 stat1=10 devices=0x30000
(cd1:ata1:0:1:0): got CAM status 0x50
(cd1:ata1:0:1:0): fatal error, failed to attach to device
(cd1:ata1:0:1:0): lost device, 4 refs
Opened disk cd1 -> 6
(cd1:ata1:0:1:0): removing device entry

First i tried some snapshots from allbsd.org, to verify that the same problem
existed with independently generated systems, then I made a search to find that
the "culprit" was:

Author: kib
Date: Tue Feb 12 16:57:20 2013
New Revision: 246713
URL: http://svnweb.freebsd.org/changeset/base/246713

Log:
   Reform the busdma API so that new types may be added without modifying
   every architecture's busdma_machdep.c.  It is done by unifying the
   bus_dmamap_load_buffer() routines so that they may be called from MI
   code.  The MD busdma is then given a chance to do any final processing
   in the complete() callback.

   The cam changes unify the bus_dmamap_load* handling in cam drivers.

   The arm and mips implementations are updated to track virtual
   addresses for sync().  Previously this was done in a type specific
   way.  Now it is done in a generic way by recording the list of
   virtuals in the map.

   Submitted by:	jeff (sponsored by EMC/Isilon)
   Reviewed by:	kan (previous version), scottl,
   	mjacob (isp(4), no objections for target mode changes)
   Discussed with:	     ian (arm changes)
   Tested by:	marius (sparc64), mips (jmallet), isci(4) on x86 (jharris),
   	amd64 (Fabian Keil <freebsd-listen at fabiankeil.de>)

I even tried to rebuild the system WITHOUT_CLANG, just to eliminate the
"compiler factor" (with r247000 applied of course).

If necessary I can send complete verbose dmesg at r245422 and r246923.

Thanks for your attention

CBu

P.S. GREAT THANKS to allbsd.org for this its very useful collection of working
memstick images ! but with the remark that the documented revision numbers seems
to be inexacts: the 246711 snapshot exhibited this same problem (?!)