svn commit: r214279 - in head: share/man/man4 sys/cam sys/cam/ata sys/kern

[Alexander Motin]

Garrett Cooper wrote:
> On Sun, Oct 24, 2010 at 10:03 AM, Alexander Motin <mav at freebsd.org> wrote:
>> Bruce Cran wrote:
>>> On Sunday 24 October 2010 17:31:58 Bruce Cran wrote:
>>>
>>>> Log:
>>>>   Mostly revert r203420, and add similar functionality into ada(4) since
>>>> the existing code caused problems with some SCSI controllers.
>> Proper way would be IMHO to fix polling in aac driver.
>>
>>>>   A new sysctl kern.cam.ada.spindown_shutdown has been added that controls
>>>>   whether or not to spin-down disks when shutting down.
>>>>   Spinning down the disks unloads/parks the heads - this is
>>>>   much better than removing power when the disk is still
>>>>   spinning because otherwise an Emergency Unload occurs which may cause
>>>> damage to the actuator.
>>> The FLUSH CACHE + STANDBY IMMEDIATE commands are issued (instead of just
>>> SLEEP) following the procedure documented in Fujitsu's MHW series product
>>> documentation under section 1.10.1, "Recommended power-off sequence".
>> Not instead of "just SLEEP", but instead of FLUSH CACHE (by respective
>> peripheral driver) + SLEEP (by xpt). It should probably be the same.
>>
>> Just for the note, SCSI specification states that STOP automatically
>> implies FLUSH CACHE. ATA - doesn't.
> 
>     I could be wrong, but I think the ANSI ATA<->SCSI spec states
> otherwise (taken from ANSI INCITS 431-2007 page 62 -- see steps 1-4):
> 
> 9.11.3 START STOP UNIT START bit LOEJ bit combinations
> The SATL shall perform the actions shown in table 40 in response to a
> START STOP UNIT command.
> Table 40 — Definition of START and LOEJ bits in the START STOP UNIT CDB
> START LOEJ Definition
> 0 0 The SATL shall:
> 1) If the IMMED bit is set to one, then return GOOD status;
> 2) Issue an ATA flush command (see 3.1.11) to the ATA device;
> 3) If the ATA flush command completes with any error, then process ending status
> according to the IMMED bit (see 9.11.2) with the additional sense code set to
> COMMAND SEQUENCE ERROR;
> 4) If the ATA flush command completes without error, then issue an ATA STANDBY
> IMMEDIATE command to the ATA Sector Count set to zero;
> 5) If the ATA STANDBY IMMEDIATE command completes with any error, then
> process ending status according to the IMMED bit (see 9.11.2) with the
> additional
> sense code set to COMMAND SEQUENCE ERROR; and
> 6) If the ATA STANDBY IMMEDIATE command completes without error and the
> IMMED bit is set to zero, then return GOOD status (see 9.11.2) a.
> 
>     Not sure about the ATA spec standalone... might be present in the ATA8 spec.

As I understand, this just confirms what I have said:
SCSI STOP == ATA FLUSH CACHE + STANDBY IMMEDIATE.
So SCSI STOP implies flush, while ATA STANDBY IMMEDIATE doesn't.

-- 
Alexander Motin