On Tue, Mar 22, 2011 at 03:54:40PM +0100, Herbert Poetzl wrote:

following up on a thread about PMP and SEP from earlier this
year, I have now prepared a test system which should allow
me to control all involved parts (i.e. SATA controller, PMP
and the SEP) for testing and debugging ...

during the initial system tests, I found some strange
behaviour, which I am unable to explain, and it might as
well be a SATA/PMP bug in Linux ...

the problem basically arises when I pull a drive from the 
enclosure (without telling Linux first), wait some time
till the kernel becomes aware of the fact, and then put it 
back into the enclosure ...

at this point, the drive indicator (PMP and the drive one)
goes on, the drive spins up, but Linux refuses to detect
the device ... I tried the following things:

 echo "- - -" >/sys/class/scsi_host/host9/scan

 scsiadd -s 9

 resetting the PMP (via small front panel button)

note that the target is still listed in sysfs:
# ls /sys/class/scsi_host/host9/device/
power/  scsi_host/  subsystem@  target9:0:0/  target9:1:0/  target9:2:0/  target9:3:0/  target9:4:0/  uevent

only way to get the device back seems to be to remove the
driver (rmmod sata_sil24) and to reload it again, which is
probably a little tricky assuming that the other disks are
in use :)

just for the fun of doing it, I tried to tell Linux first that
the drive will be removed (via scsiadd -r) and discovered that
this causes an even stranger effect:

# scsiadd -r 13 4 0 0		; seems to remove the target
# scsiadd -a 13 4 0 0		; seems to add back the target

Host: scsi13 Channel: 04 Id: 00 Lun: 00
  Vendor: ATA      Model: ST31000340AS     Rev: SD15
  Type:   Direct-Access                    ANSI  SCSI revision: 05

and sometimes, the devices comes back with a different device
entry but the same scsi bus/chan/id/lun, in which case, it
cannot be removed via scsiadd -r anymore, as it just returns

 could not remove device 13 4 0 0 : No such device or address

also note that this doesn't change the fact that the device is
lost till the driver is reloaded once it is unplugged ...

many thanks in advance,
Herbert

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