BusLogic SCSI Driver for Linux 1.3.41
Version 1.3.0 ~ 13 November 1995
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 technology are not supported by this
driver.
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 by anonymous
FTP from ftp.dandelion.com. While directory listings are not permitted, the
introductory banner displayed on anonymous FTP login will provide a list of the
driver versions and any other files 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.
I have recently had conversations with the Senior Product Marketing Manager at
BusLogic regarding the needs of free software developers, and he has reaffirmed
BusLogic's committment to providing the technical information and support we
need to take full advantage of their products. BusLogic has also been very
accomodating in providing technical documentation, as well as access to their
engineering staff for technical questions and advice. In addition, they have
loaned me ISA cards for configuration testing, and even allowed me use of their
technical support lab to test EISA configurations, since I don't have an EISA
system. Their interest and support is greatly appreciated.
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 maximum
number of concurrent commands per logical unit is available from the kernel
command line. In addition, tagged queuing is automatically disabled whenever
the host adapter firmware version is known not to implement it correctly, or
whenever a concurrency value of 1 is selected. 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. By default, when
the higher level parts of the SCSI subsystem request that a command be reset,
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 device based on
the recommendation of the SCSI subsystem. Error recovery options are
selectable from the kernel command line individually for each target device,
and also include forcing a full host adapter hard reset and SCSI bus reset,
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 option 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 reinitialization. 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.
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 1.3.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.
"C" Series Host Adapters:
946C PCI Fast Single-ended SCSI-2
956C PCI Fast/Wide Single-ended SCSI-2
956CD PCI Fast/Wide Differential SCSI-2
445C VLB Fast Single-ended SCSI-2
747C EISA Fast Single-ended SCSI-2
757C EISA Fast/Wide Single-ended SCSI-2
757CD EISA Fast/Wide Differential SCSI-2
545C ISA Fast Single-ended SCSI-2
540CF ISA Fast Single-ended SCSI-2
"S" Series Host Adapters:
445S VLB Fast Single-ended SCSI-2
747S EISA Fast Single-ended SCSI-2
747D EISA Fast Differential SCSI-2
757S EISA Fast/Wide Single-ended SCSI-2
757D EISA Fast/Wide Differential SCSI-2
545S ISA Fast Single-ended SCSI-2
542D ISA Fast Differential SCSI-2
742A EISA Single-ended SCSI-2 (742A revision H)
542B ISA Single-ended SCSI-2 (542B revision H)
"A" Series Host Adapters:
742A EISA Single-ended SCSI-2 (742A revisions A - G)
542B ISA Single-ended SCSI-2 (542B revisions A - G)
The FlashPoint LT, also known as the 930 Ultra, implements a different host
interface and is not supported by this driver.
AMI FastDisk Host Adapters are true BusLogic clones and are supported by this
driver.
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 concurrency of 1 which also
disables tagged queuing. It may be useful if problems arise during
installation on a system with a flakey 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 "C" series
boards. 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=0,0,10"
This command line selects default probing and concurrency but changes the
bus settle time to 10 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.
"BusLogic=TQ:Disable"
This command line selects default probing and disables tagged queuing,
while keeping the default concurrency.
"BusLogic=0,15,TQ:N"
This command line selects a concurrency of 15 and disables tagged queuing
for target 0, while allowing tagged queuing for all other target devices.
Note that limiting the concurrency to 1 or disabling tagged queuing can
substantially impact performance.
INSTALLATION
This distribution was prepared for Linux kernel version 1.3.41. Installation
in later versions will probably be successful as well, though BusLogic.patch
may not be required once this driver becomes part of the standard development
kernel; installation in earlier versions should not be attempted as 1.3.41
contains changes I made to the common code that are essential for correct error
recovery.
To install the BusLogic SCSI driver, you may use the following commands,
replacing "/usr/src" with wherever you keep your Linux kernel source tree:
cd /usr/src
tar -xvzf BusLogic-1.3.0.tar.gz
mv README.BusLogic BusLogic.[ch] linux/drivers/scsi
patch -p < BusLogic.patch
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, you may omit the "make config" step above.
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