the adapter's selections. Many fast periferals were getting upset when
the sequencer decided to rearbitrate after the device had already won
arbitration. This also forced the creation of a list threaded through
the SCBs (since we don't have enough space anywhere else) of commands that
are awaiting reselection. This list is run down before any new transactions
from the input queue are allowed. The list is appened to whenever we begin
a selection (simple case since the selecting device is always at the head)
and by the kernel driver whenever a request sense occurs. In the common
case, the list is only one element long, but when a reselection wins out
over a selection and that reselection generates a request sense, the
outstanding selection required for the retreval of the sense code grows
the list. On machines with many targets, this might cause the list to grow
large, so this solution, which will allow up to the maximum number of I/O
requests capible of the card elements in the list, was chosen. The list
manipulation is trivial and adds three sequencer instructions of overhead
to the selection phase.
This fixes the "target busy" errors from micropolis drives and the bursty
I/O problem when performing I/O between a Quantum Grand Prix and any other
device. I anticipate that this will correct many of the problems that
have been reported with this driver.
Reviewed by: Wcarchive and David Greenman
is identical to the older version, just the copyright has changed. Many
thanks go to Dean Gehnert of the Linux camp who went the extra mile to make
this happen.
Other changes:
Update assembler man page to include the -v and -D options
Merge in Dean's latest changes to the assembler
Have the sequencer do a MSG_REJECT when the negotiated syncronous rate
is lower than the adapter supports. This forces asyncronous mode which
is faster at these rates anyway.
This code will be moved shortly to the non-gpld portion of the tree.
old value.
Remove unnecessary check for active messages in setup SCB. This same test
would also jump to p_mesgin_done which would "ACK" an extra time possibly
confusing the target.
Tell the kernel driver whenever we send an ABORT_TAG message.
- Report valid residual byte counts. We actually pause the sequencer
when the residual is non-zero. I thought about using DMA to do this,
bus sequencer program space is tight.
- Fix embarassing off by one error in the computation of a 2's
compliment variable. This was most likely the cause of the
many problems reported with the tagged queuing code.
- Handle "MAX_SYNC" as a special case (ie we are the ones starting
the sync negotiation sequence). This was done so that the target
scratch area can be initialed to 0 offset (asyncronous transfers)
safely. The initialization to 0 (was 15) is necessary since in
some cases a Wide negotiation could run into problems if SCSIRATE
was set wrong and we went into data(in/out).
- Trim the DMA routines a little by using some procedures. Net
effect is more functionality with 3 less instructions after this
update.
- Toggle the WIDEODD bit of the DFCNTRL whenever this is not the
last SG block. It has no effect in the 8bit bus configuration,
but in the Wide configuration ensures that the overlap byte is
held in the SCSI block if the transfer is odd so it will end
up in the next SG (the correct behavior).
Print out the length of the compiled sequencer program.
aic7xxx.seq:
More optimizations. Replace generic bcopy routine with bcopy_3
and bcopy_4 (ie unroll the loops) since these are the only two cases used.
Initialize SIMODE1 and SXFRCTL1 from the kernel in ahc_init instead of
at each selection/reselection since this is expensive and only needs to
be done once. Condense function returns into previous instruction if possible.
Reorder some sections to kill superflous jumps. These optimizations kill
the ~150k/s penalty adding support for Twin/Wide cards was costing since
the last place in the commaon path of execution where we had to do ugly,
convoluted testing for the type of card in the sequencer has gone away.
Next stop tagged queuing and target mode.
(SCSI control block) instead of having the host PIO it down. Also
reimplement WDTR and SDTR optimization to remove code in the sequencer
and place the responsibility of knowing when to initiate SDTR or WDTR
on the kernel driver. This vastly shortens the sequencer program yet
yeilds the same performance.
sense retrieval code that messed up CDROM devices. This code will also
responde correctly to SDTR and WDTR messages from devices that start a
negotiation sequence.
You can now sling 14 devices off of a 274xT. In the process of adding
twin channel support, I removed all evident restrictions on supporting
Wide channeled devices, but I do not have a Wide controller to test them
on.
aic7770_seq.h, the pre-compiled header, is no longer needed since config
handles this dependancy.
make the sequencer code fully compatible with the aic7870 (ie 294x adaptors).
I've also added to my local mods putting the sequencer into "FASTMODE" clock.
This gives upwards of 2M/sec write preformance improvement in some scenarios.
There haven't been any reports of this causing problems, and I have been
reaping the benifits of it for more than a week now.
This also includes a new version of the pre-generated file <ugh>
Obtained from: John Aycock (aycock@cpsc.ucalgary.ca) and myself
a discussion going on about removing this code from the burden of the
GPL, but it won't happen before Beta, and this code should be tested
before release.
Supports 27/2842 class adaptec cards and is almost capable of supporting
aic7870 based adapters (294X series cards). It does not support Wide
controllers or the second channel on Twin boards although I have work in
progress on getting both channels and running.
I have also added a few performance improvements to this version that give
us approximately a 25% boost over the original driver. These patches have
been submitted to the author.
Obtained from: Linux aic7770 driver (John Aycock - aycock@cpsc.ucalgary.ca)
