define). Fix stupidity wrt checking whether we've gone to
LOOP_PDB_RCVD loopstate- it's okay to be greater than this state.
D'oh! Protect calls to isp_pdb_sync and isp_fclink_state with IS_FC
macros.
Completely redo mailbox command routine (in preparation to make this
possibly wait rather than poll for completion).
Make a major attempt to solve the 'lost interrupt' problem
1. Problem
The Qlogic cards would appear to 'lose' interrupts, i.e., a legitimate
regular SCSI command placed on the request queue would never complete
and the watchdog routine in the driver would eventually wakeup and
catch it. This would typically only happen on Alphas, although a
couple folks with 700MHz Intel platforms have also seen this.
For a long time I thought it was a foulup with f/w negotiations of
SYNC and/or WIDE as it always seemed to happen right after the
platform it was running on had done a SET TARGET PARAMETERS mailbox
command to (re)enable sync && wide (after initially forcing
ASYNC/NARROW at startup). However, occasionally, the same thing
would also occur for the Fibre Channel cards as well (which, ahem,
have no SET TARGET PARAMETERS for transfer mode).
After finally putting in a better set of watchdog routines for the
platforms for this driver, it seemed to be the case that the command
in question (usually a READ CAPACITY) just had up and died- the
watchdog routine would catch it after ~10 seconds. For some platforms
(NetBSD/OpenBSD)- an ABORT COMMAND mailbox command was sent (which
would always fail- indicating that the f/w denied knowledge of this
command, i.e., the f/w thought it was a done command). In any case,
retrying the command worked. But this whole problem needed to be
really fixed.
2. A False Step That Went in The Right Direction
The mailbox code was completely rewritten to no longer try and grab
the mailbox semaphore register and to try and 'by hand' complete
async fast posting completions. It was also rewritten to now have
separate in && out bitpatterns for registers to load to start and
retrieve to complete. This means that isp_intr now handles mailbox
completions.
This substantially simplifies the mailbox handling code, and carries
things 90% toward getting this to be a non-polled routine for this
driver.
This did not solve the problem, though.
3. Register Debouncing
I saw some comments in some errata sheets and some notes in a Qlogic
produced Linux driver (for the Qlogic 2100) that seemed to indicate
that debouncing of reads of the mailbox registers might be needed,
so I added this. This did not affect the problem. In fact, it made
the problem worse for non-2100 cards.
5. Interrupt masking/unmasking
The driver *used* to do a substantial amount of masking/unmasking
of the interrupt control register. This was done to make sure that
the core common code could just assume it would never get pre-empted.
This apparently substantially contributed to the lost interrupt
problem. The rewrite of the ICR (Interrupt Control Register),
which is a separate register from the ISR (Interrupt Status Register)
should not have caused any change to interrupt assertions pending.
The manual does not state that it will, and the register layout
seems to imply that the ICR is just an active route gate. We only
enable PCI Interrupts and RISC Interrupts- this should mean that
when the f/w asserts a RISC interrupt and (and the ICR allows RISC
Interrupts) and we have PCI Interrupts enabled, we should get a
PCI interrupt. Apparently this is a latch- not a signal route.
Removing this got rid of *most* but not all, lost interrupts.
5. Watchdog Smartening
I made sure that the watchdog routine would catch cases where the
Qlogic's ISR showed an interrupt assertion. The watchdog routine
now calls the interrupt service routine if it sees this. Some
additional internal state flags were added so that the watchdog
routine could then know whether the command it was in the middle
of burying (because we had time it out) was in fact completed by
the interrupt service routine.
6. Occasional Constipation Of Commands..
In running some very strenous high IOPs tests (generating about
11000 interrupts/second across one Qlogic 1040, one Qlogic 1080
and one Qlogic 2200 on an Alpha PC164), I found that I would get
occasional but regular 'watchdog timeouts' on both the 1080 and
the 2100 cards. This is under FreeBSD, and the watchdog timeout
routine just marks the command in error and retries it.
Invariably, right after this 'watchdog timeout' error, I'd get a
command completion for the command that I had thought timed out.
That is, I'd get a command completion, but the handle returned by
the firmware mapped to no current command. The frequency of this
problem is low under such a load- it would usually take an 30
minutes per 'lost' interrupt.
I doubled the timeout for commands to see if it just was an edge
case of waiting too short a period. This has no effect.
I gathered and printed out microtimes for the watchdog completed
command and the completion that couldn't find a command- it was
always the case that the order of occurrence was "timeout, completion"
separated by a time on the order of 100 to 150 ms.
This caused me to consider 'firmware constipation' as to be a
possible culprit. That is, resubmission of a command to the device
that had suffered a watchdog timeout seemed to cause the presumed
dead command to show back up.
I added code in the watchdog routine that, when first entered for
the command, marks the command with a flag, reissues a local timeout
call for one second later, but also then issues a MARKER Request
Queue entry to the Qlogic f/w. A MARKER entry is used typically
after a Bus Reset to cause the f/w to get synchronized with respect
to either a Bus, a Nexus or a Target.
Since I've added this code, I always now see the occasional watchdog
timeout, but the command that was about to be terminated always
now seems to be completed after the MARKER entry is issued (and
before the timeout extension fires, which would come back and
*really* terminate the command).
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