		  BusLogic MultiMaster SCSI Driver for Linux

		       Version 1.2.6 for Linux 1.2.13
		       Version 2.0.6 for Linux 2.0.4

				 17 July 1996

			       Leonard N. Zubkoff
			       Dandelion Digital
			       lnz@dandelion.com

	   Copyright 1995 by Leonard N. Zubkoff <lnz@dandelion.com>


				 INTRODUCTION

BusLogic, Inc. designs and manufactures a variety of high performance SCSI host
adapters which share a common programming interface across a diverse collection
of bus architectures by virtue of their MultiMaster ASIC technology.  This
driver supports all present BusLogic MultiMaster Host Adapters, and should
support any future MultiMaster designs with little or no modification.  Host
adapters based on the new FlashPoint architecture are not supported by this
driver; consult the README.FlashPoint file for information about a program to
upgrade Linux users from the unsupported FlashPoint LT to the supported BT-948.

My primary goals in writing this completely new BusLogic driver for Linux are
to achieve the full performance that BusLogic SCSI Host Adapters and modern
SCSI peripherals are capable of, and to provide a highly robust driver that can
be depended upon for high performance mission critical applications.  All of
the major performance and error recovery features can be configured from the
Linux kernel command line, allowing individual installations to tune driver
performance and error recovery to their particular needs.

The most recent versions of this driver will always be available from my Linux
Home Page at URL "http://www.dandelion.com/Linux/" and by anonymous FTP from
ftp.dandelion.com.  While only limited FTP directory listings are permitted,
the introductory banner displayed on anonymous FTP login will provide a list of
the driver versions and any other files that are available for retrieval.

Bug reports should be sent via electronic mail to "lnz@dandelion.com".  Please
include with the bug report the complete configuration messages reported by the
driver and SCSI subsystem at startup, along with any subsequent system messages
relevant to SCSI operations, and a detailed description of your system's
hardware configuration.

BusLogic has been an excellent company to work with and I highly recommend
their products to the Linux community.  In November 1995, I was offered the
opportunity to become a beta test site for their latest MultiMaster product,
the BT-948 PCI Ultra SCSI Host Adapter, and then again for the BT-958 PCI Wide
Ultra SCSI Host Adapter in January 1996.  This was mutually beneficial since
BusLogic received a degree and kind of testing that their own testing group
cannot readily achieve, and the Linux community has available high performance
host adapters that have been well tested with Linux even before being brought
to market.  This relationship has also given me the opportunity to interact
directly with their technical staff, to understand more about the internal
workings of their products, and in turn to educate them about the needs and
potential of the Linux community.  Their interest and support is greatly
appreciated.

Unlike some other vendors, if you contact BusLogic Technical Support with a
problem and are running Linux, they will not tell you that your use of their
products is unsupported.  Their latest product marketing literature even states
"BusLogic SCSI host adapters are compatible with all major operating systems
including: ... Linux ...".

BusLogic, Inc. is located at 4151 Burton Drive, Santa Clara, California, 95054,
USA and can be reached by Voice at 408/492-9090 or by FAX at 408/492-1542.
BusLogic maintains a World Wide Web site at http://www.buslogic.com, an
anonymous FTP site at ftp.buslogic.com, and a BBS at 408/492-1984.  BusLogic
Technical Support can be reached by electronic mail at techsup@buslogic.com, by
Voice at 408/654-0760, or by FAX at 408/492-1542.  Contact information for
offices in Europe and Japan is available on the Web site.


				DRIVER FEATURES

o Configuration Reporting and Testing

  During system initialization, the driver reports extensively on the host
  adapter hardware configuration, including the synchronous transfer parameters
  negotiated with each target device.  In addition, the driver tests the
  hardware interrupt configuration to verify that interrupts are actually
  delivered correctly to the interrupt handler.  This should catch a high
  percentage of PCI motherboard configuration errors early, because when the
  host adapter is probed successfully, most of the remaining problems appear to
  be related to interrupts.  Most often, any remaining hardware problems are
  related to the specific configuration of devices on the SCSI bus, and the
  quality of cabling and termination used.  Finally, this BusLogic driver
  should never incorrectly attempt to support an Adaptec 154x Host Adapter.

o Performance Features

  BusLogic SCSI Host Adapters directly implement SCSI-2 Tagged Queuing, and so
  support has been included in the driver to utilize tagged queuing with any
  target devices that report having the tagged queuing capability.  Tagged
  queuing allows for multiple outstanding commands to be issued to each target
  device or logical unit, and can improve I/O performance substantially.  In
  addition, BusLogic's Strict Round Robin Mode is used to optimize host adapter
  performance, and scatter/gather I/O can support as many segments as can be
  effectively utilized by the Linux I/O subsystem.  Control over the use of
  tagged queuing for each target device as well as selection of the tagged
  queue depth is available from the kernel command line.  By default, the queue
  depth is automatically determined based on the number, type, speed, and
  capabilities of the target devices found.  In addition, tagged queuing is
  automatically disabled whenever the host adapter firmware version is known
  not to implement it correctly, or whenever a tagged queue depth of 1 is
  selected.  Tagged queuing is also disabled for individual target devices if
  disconnect/reconnect is disabled for that device.  In performance testing,
  sustained disk writes of 7.3MB per second have been observed to a /dev/sd
  device.

o Robustness Features

  The driver implements extensive error recovery procedures.  When the higher
  level parts of the SCSI subsystem request that a command be reset, action is
  taken to restore proper operation of the host adapter and SCSI bus.  On Linux
  1.2.13, by default a full host adapter hard reset and SCSI bus reset is
  performed.  On Linux 2.0.x, by default a selection is made between a full
  host adapter hard reset and SCSI bus reset versus sending a bus device reset
  message to the individual target device based on the recommendation of the
  SCSI subsystem.  Error recovery strategies are selectable from the kernel
  command line individually for each target device, and also include sending a
  bus device reset to the specific target device associated with the command
  being reset, as well as suppressing error recovery entirely to avoid
  perturbing an improperly functioning device.  If the bus device reset error
  recovery strategy is selected and sending a bus device reset does not restore
  correct operation, the next command that is reset will force a full host
  adapter hard reset and SCSI bus reset.  SCSI bus resets caused by other
  devices and detected by the host adapter are also handled by issuing a hard
  reset to the host adapter and full re-initialization.  Finally, if tagged
  queuing is active and more than one command reset occurs in a 10 minute
  interval, or if a command reset occurs within the first 10 minutes of
  operation, then tagged queuing will be disabled for that target device.
  These error recovery options should improve overall system robustness by
  preventing individual errant devices from causing the system as a whole to
  lock up or crash, and thereby allowing a clean shutdown and restart after the
  offending component is removed.

o Extensive Testing

  This driver has undergone extensive testing and improvement over a period of
  several months, and is routinely being used on heavily loaded systems.  Over
  300 people retrieved the driver during the beta test period.  In addition to
  testing in normal system operation, error recovery tests have been performed
  to verify proper system recovery in the case of simulated dropped interrupts,
  external SCSI bus resets, and SCSI command errors due to bad CD-ROM media.

o PCI Configuration Support

  On PCI systems running kernels compiled with PCI BIOS support enabled, this
  driver will interrogate the PCI configuration space and use the I/O port
  addresses assigned by the system BIOS, rather than the ISA compatible I/O
  port addresses.  The ISA compatible I/O port address is then disabled by the
  driver.  On PCI systems it is also recommended that the AutoSCSI utility be
  used to disable the ISA compatible I/O port entirely as it is not necessary.
  The ISA compatible I/O port is disabled by default on the BT-948/958/958D.

o Shared Interrupts Support

  On systems that support shared interrupts, any number of BusLogic Host
  Adapters may share the same interrupt request channel, and in fact it is more
  efficient if they do so.  The driver scans all known BusLogic Host Adapters
  whenever an interrupt is handled on an interrupt channel assigned to any
  BusLogic Host Adapter.

o Wide SCSI Support

  All BusLogic MultiMaster SCSI Host Adapters share a common programming
  interface, except for the inevitable improvements and extensions as new
  models are released, so support for Wide SCSI data transfer has automatically
  been available without explicit driver support.  When used with Linux 2.0.x,
  this driver adds explicit support for up to 15 target devices and 64 logical
  units per target device, to fully exploit the capabilities of the newest
  BusLogic Wide SCSI Host Adapters.


			    SUPPORTED HOST ADAPTERS

The following list comprises the supported BusLogic SCSI Host Adapters as of
the date of this document.  It is recommended that anyone purchasing a BusLogic
Host Adapter not in the following table contact the author beforehand to verify
that it is or will be supported.

"W" Series Host Adapters:

BT-948	    PCI	    Ultra Fast Single-ended SCSI-2
BT-958	    PCI	    Ultra Wide Single-ended SCSI-2
BT-958D	    PCI	    Ultra Wide Differential SCSI-2

"C" Series Host Adapters:

BT-946C	    PCI	    Fast Single-ended SCSI-2
BT-956C	    PCI	    Fast Wide Single-ended SCSI-2
BT-956CD    PCI	    Fast Wide Differential SCSI-2
BT-445C	    VLB	    Fast Single-ended SCSI-2
BT-747C	    EISA    Fast Single-ended SCSI-2
BT-757C	    EISA    Fast Wide Single-ended SCSI-2
BT-757CD    EISA    Fast Wide Differential SCSI-2
BT-545C	    ISA	    Fast Single-ended SCSI-2
BT-540CF    ISA	    Fast Single-ended SCSI-2

"S" Series Host Adapters:

BT-445S	    VLB	    Fast Single-ended SCSI-2
BT-747S	    EISA    Fast Single-ended SCSI-2
BT-747D	    EISA    Fast Differential SCSI-2
BT-757S	    EISA    Fast Wide Single-ended SCSI-2
BT-757D	    EISA    Fast Wide Differential SCSI-2
BT-545S	    ISA	    Fast Single-ended SCSI-2
BT-542D	    ISA	    Fast Differential SCSI-2
BT-742A	    EISA    Single-ended SCSI-2 (742A revision H)
BT-542B	    ISA	    Single-ended SCSI-2 (542B revision H)

"A" Series Host Adapters:

BT-742A	    EISA    Single-ended SCSI-2 (742A revisions A - G)
BT-542B	    ISA	    Single-ended SCSI-2 (542B revisions A - G)

The FlashPoint LT, also known as the BT-930 Ultra, implements a different host
interface and is not supported by this driver.  Consult the README.FlashPoint
file for information about a program to upgrade Linux users from the
unsupported FlashPoint LT to the supported BT-948.

AMI FastDisk Host Adapters that are true BusLogic clones are supported by this
driver.


		      BT-948/958/958D INSTALLATION NOTES

The BT-948/958/958D PCI Ultra SCSI Host Adapters have some features which may
require attention in some circumstances when installing Linux.

o PCI I/O Port Assignments

  When configured to factory default settings, the BT-948/958/958D will only
  recognize the PCI I/O port assignments made by the motherboard's PCI BIOS.
  The BT-948/958/958D will not respond to any of the ISA compatible I/O ports
  that previous BusLogic SCSI Host Adapters respond to.  This driver supports
  the PCI I/O port assignments, so this is the preferred configuration.
  However, if the obsolete BusLogic driver must be used for any reason, such as
  a Linux distribution that does not yet use this driver in its boot kernel,
  BusLogic has provided an AutoSCSI configuration option to enable a legacy ISA
  compatible I/O port.

  To enable this backward compatibility option, invoke the AutoSCSI utility via
  Ctrl-B at system startup and select "Adapter Configuration", "View/Modify
  Configuration", and then change the "ISA Compatible Port" setting from
  "Disable" to "Primary" or "Alternate".  Once this driver has been installed,
  the "ISA Compatible Port" option should be set back to "Disable" to avoid
  possible future I/O port conflicts.  The older BT-946C/956C/956CD also have
  this configuration option, but the factory default setting is "Primary".

o PCI Slot Scanning Order

  In systems with multiple BusLogic PCI Host Adapters, the order in which the
  PCI slots are scanned may appear reversed with the BT-948/958/958D as
  compared to the BT-946C/956C/956CD.  For booting from a SCSI disk to work
  correctly, it is necessary that the host adapter's BIOS and the kernel agree
  on which disk is the boot device, which requires that they recognize the PCI
  host adapters in the same order.  The motherboard's PCI BIOS provides a
  standard way of enumerating the PCI host adapters, which is used by the Linux
  kernel.  Some PCI BIOS implementations enumerate the PCI slots in order of
  increasing bus number and device number, while others do so in the opposite
  direction.

  Unfortunately, Microsoft decided that Windows 95 would always enumerate the
  PCI slots in order of increasing bus number and device number regardless of
  the PCI BIOS enumeration, and requires that their scheme be supported by the
  host adapter's BIOS to receive Windows 95 certification.  Therefore, the
  factory default settings of the BT-948/958/958D enumerate the host adapters
  by increasing bus number and device number.  To disable this feature, invoke
  the AutoSCSI utility via Ctrl-B at system startup and select "Adapter
  Configuration", "View/Modify Configuration", press Ctrl-F10, and then change
  the "Use Bus And Device # For PCI Scanning Seq." option to OFF.

  This driver will interrogate the setting of the PCI Scanning Sequence option
  so as to recognize the host adapters in the same order as they are enumerated
  by the host adapter's BIOS.


			     COMMAND LINE OPTIONS

Many features of this driver are configurable by specification of appropriate
kernel command line options.  A full description of the command line options
may be found in the comments before BusLogic_Setup in the kernel source code
file "BusLogic.c".  The following examples may be useful as a starting point:

  "BusLogic=0x330"

    This command line limits probing to the single I/O port at 0x330.

  "BusLogic=0,1"

    This command line selects default probing and a tagged queue depth of 1
    which also disables tagged queuing.  It may be useful if problems arise
    during installation on a system with a flaky SCSI configuration.  In cases
    of a marginal SCSI configuration it may also be beneficial to disable fast
    transfers and/or synchronous negotiation using AutoSCSI on "W" and "C"
    series controllers.  Disconnect/reconnect may also be disabled for fast
    devices such as disk drives, but should not be disabled for tape drives or
    other devices where a single command may take over a second to execute.

  "BusLogic=0,0,30"

    This command line selects default probing and automatic tagged queue depth
    selection, but changes the bus settle time to 30 seconds.  It may be useful
    with SCSI devices that take an unusually long time to become ready to
    accept commands after a SCSI bus reset.  Some tape drives will not respond
    properly immediately after a SCSI bus reset, especially if a tape is
    present in the drive.

  "BusLogic=TQ:Disable"

    This command line selects default probing and disables tagged queuing.

  "BusLogic=0,15,TQ:N"

    This command line selects a tagged queue depth of 15 and disables tagged
    queuing for target 0, while allowing tagged queuing for all other target
    devices.

Note that limiting the tagged queue depth or disabling tagged queuing can
substantially impact performance.


				 INSTALLATION

This distribution was prepared for Linux kernel version 1.2.13
(BusLogic-1.2.6.tar.gz) or Linux kernel version 2.0.4 (BusLogic-2.0.6.tar.gz).
Installation in later versions will probably be successful as well, though
BusLogic.patch may not be required.  Installation in earlier versions is not
recommended.

To install the BusLogic SCSI driver, you may use the following commands,
replacing "/usr/src" with wherever you keep your Linux kernel source tree
(substitute "1.2" or "2.0" for "x.y" in the tar command as appropriate):

  cd /usr/src
  tar -xvzf BusLogic-x.y.6.tar.gz
  mv README.* BusLogic.[ch] linux/drivers/scsi
  patch -p < BusLogic.patch	    (on Linux 1.2.13 only)
  patch -p < BusLogic.elf_patch	    (on Linux 1.2.13 ELF systems only)
  cd linux
  make config
  make depend
  make zImage

Then install "arch/i386/boot/zImage" as your standard kernel, run lilo if
appropriate, and reboot.

Be sure to answer "y" to the "BusLogic SCSI support" query during the "make
config" step.  If your system was already configured for the old BusLogic
driver or for an older version of this driver, you may omit the "make config"
step above.


		      BUSLOGIC ANNOUNCEMENTS MAILING LIST

The BusLogic Announcements Mailing List provides a forum for informing Linux
users of new driver releases and other announcements regarding Linux support
for BusLogic SCSI Host Adapters.  To join the mailing list, send a message to
"buslogic-announce-request@dandelion.com" with the line "subscribe" in the
message body.
