SUBJECT
-------
AM53/79C974 PC-SCSI Driver


DISCLAIMER
----------
***  THIS SHOULD BE CONSIDERED AS BETA SOFTWARE  ***
***  USE AT YOUR OWN RISK!                       ***


Copyright
---------
The architecture and much of the code of this device driver was 
originally developed by Drew Eckhardt for the NCR5380. The 
following copyrights apply:

For the architecture and all pieces of code which can also be found 
in the NCR5380 device driver:
Copyright 1993, Drew Eckhardt
  Visionary Computing 
  (Unix and Linux consulting and custom programming)
  drew@colorado.edu
  +1 (303) 666-5836
 
The AM53C974_nobios_detect code was originally developed by
Robin Cutshaw (robin@xfree86.org) and is used here in a 
slightly modified form.
 
For the remaining code:
  Copyright 1994, D. Frieauff
  EMail: fri@rsx42sun0.dofn.de
  Phone: x49-7545-8-2256 , x49-7541-42305


Version
-------
AM53/79C974 (PC-SCSI) Linux driver ALPHA release 0.5, 19 November 1995


Changelog
---------
0.1 -> 0.2: 
  - Extended message handling re-written to eliminate 'invalid message 17' bug
  - Parameters of AM53C974_intr adapted
  - Debug messages structured
  - Spelling improved
0.2 -> 0.3:
  - README file updated -- please read this file up to the end!
  - Automatic scanning of io_port and irq implemented; no need for BIOS32 
    anymore
  - Improved configuration (now via LILO parameter string)
  - Cleanup of probing and initialization code
  - Improved sync. negotiation (can be setup individually for every device)
  - Improved/ debugged code for reception of ext. messages
0.3 -> 0.4:
  - Improved PCI probing and initialization code
  - Compatibility changes for Linux 1.3.x
0.4 -> 0.5:
  - Compatibility changes for Linux 1.3.42


Bugs & Todo
-----------
 - Add proc info function
 - Support SCSI-2 tagged queuing
 - Finalize abort code 


Features
--------
This driver supports asynchronous and synchronous SCSI-I and SCSI-II
devices.  It is capable of transfer rate and synchronous negotiation
(see below).  The driver supports scatter-gather.  Transfers are DMA
based, but do not (yet) make use of the AM53/79C974 MDL mode.
Max. transfer rate is 10MHz (whatever this is in real life).  The
transfer rate is negotiated with each device (see dmesg output).  The
AM53/79C974 has a 96-byte DMA FIFO to the PCI bus and a 16-byte SCSI
FIFO.  It provides active negation and glitch suppression functions.
Burst DMA transfer rate is 132 MBytes/sec.


Configuration
-------------

The following communication characteristics can be set individually
for every SCSI device on the bus:

  - enable/disable sync. negotiation
  - transfer rate
  - asynchronous or synchronous communication
  - in case of sync. communication, the sync. offset

The sync. offset specifies the number of bytes that can be sent or 
received from the SCSI bus without ACK resp. REQ signal.
CAUTION: USING SYNCHRONOUS MODE ON LONG SCSI CABLES MAY CAUSE 
         COMMUNICATION PROBLEMS LEADING TO LOSS OF DATA. 

The default setting of the SCSI communication parameters is as follows:
  - no negotiation
  - 5.0 MHz transfer rate
  - asynchronous mode
  - zero offset

The parameters can be modified by passing a string with the following
syntax to the kernel:

	AM53C974=host-scsi-id,target-scsi-id,max-rate,max-offset

The parameters will be used by the driver as negotiation basis.  The
range of the rate parameter is 3 to 10 MHz.  The range of the
sync. offset parameter is 0 to 15 bytes. A value of 0 denotes
asynchronous comm. mode.  If the target cannot cope with the specified
transfer rate, sync. mode or sync.  offset, the negotiation result
will differ from the specified values.  The negotiation result is
printed out at the end of the negotiation process (to read it, use the
dmesg program or the appropriate syslog).  The parameter strings
(blank separated) can be passed to the kernel at the LILO prompt, or
as part of the LILO configuration file.

For example, the string "AM53C974=7,2,8,15" would be interpreted as
follows:

For communication between the controller with SCSI-ID 7 and the
device with SCSI-ID 2 a transfer rate of 8MHz in synchronous mode with
max. 15 bytes offset should be negotiated.

As an example, here my LILO configuration file:
  boot = /dev/sda
  compact
  #prompt
  delay = 50	# optional, for systems that boot very quickly
  vga = normal	# force sane state
  ramdisk = 0	# paranoia setting
  root = current  # use "current" root
  image = /usr/src/linux/arch/i386/boot/zImage
    label = linux
    append = "AM53C974=7,0,10,0 AM53C974=7,1,10,0 AM53C974=7,2,10,15 AM53C974=7,4,10,0 AM53C974=7,5,10,0"
    read-only
  other = /dev/sda4
    label = os2
  other = /dev/sdb3
    loader = /boot/any_d.b
    table = /dev/sdb
    label = setup

The same parameters at the LILO prompt:

  LILO boot: linux AM53C974=7,0,10,0 AM53C974=7,1,10,0 AM53C974=7,2,10,15 AM53C974=7,4,10,0 AM53C974=7,5,10,0

You can override parameters specified in the LILO configuration file
by parameters specified on the LILO command line.


BIOS usage
----------
Version 0.4 of the driver will use the BIOS, if available. Otherwise
it will try its internal PCI scan and access routines.  The driver
assumes that the controller's SCSI-ID (usually 7) has been correctly
loaded by the BIOS into the controller's register during system
boot. If the driver detects that the controller's SCSI ID is not '7'
it will print out a warning. If this happens to you please correct
setting of the controller's SCSI-ID. If it is wrong, then edit the
AM53C974_SCSI_ID definition in file AM53C974.h accordingly.


Test environment
----------------
This driver was tested on a Compaq XL566 with the following SCSI configuration:
2 x HP C2247 fixed disk (internal, rate=10MHz, async.)
1 x Micropolis 1624 fixed disk (external, rate=8MHz, sync., offset=15 bytes)
1 x Wangtek W5525ES cartridge streamer (internal, rate=5MHz, async.)
1 x Toshiba XM-3301B CD-ROM (external, rate=5MHz, async.)


Known problems
--------------
 - Compaq/Matsushita CD-ROM:
   Use of this device with AM53C974 driver version 0.2 caused the kernel to
   hang during Linux boot. If you encounter the problem, don't enable sync.
   negotiation with the CD-ROM, i.e. simply don't specify comm. parameters 
   for this device on the LILO command line or configuration file. 
   The driver will thus use its default for the CD-ROM, which is 5MHz 
   transfer rate async and no sync. negotiation.
 - Some disks cause problems.


What to do if there is a SCSI problem possibly related to the driver
--------------------------------------------------------------------

Read Klaus Liedl's WWW page (http://www-c724.uibk.ac.at/XL/).  In case
this does not help: Send me a complete description of the problem,
including your SCSI configuration plus as much debugging information
as possible.  Don't wait until I ask you for this information. To
enable the generation of debugging output, remove the comments from
the following definitions in the AM53C974.h file:

    AM53C974_DEBUG
    AM53C974_DEBUG_MSG
    AM53C974_DEBUG_KEYWAIT
    AM53C974_DEBUG_INFO
    AM53C974_DEBUG_INTR

With these definitions enabled, the driver will enter single-step mode
during Linux boot. Use the spacebar for stepping.  Take note of at
least the last 10 printout sections (marked by dashes) before the
crash/hangup or whatever happens and send me all of this information
via email. If the system can boot, use the syslogd daemon to record
the debugging output. Maybe you can use the ramdisk for this purpose
too (if necessary, kindly ask K. Liedl (Klaus.Liedl@uibk.ac.at) for
support, he knows how to do it -- I never tried). Stay in email
contact with me. Be aware that the following weeks/months could be the
worst of your life.  Note: If single-stepping takes up too much time,
you can try to let the driver catch the problem by pressing the 'r'
key. The driver will automatically enter single-step mode if it has
detected something weird.


Author's Contact Address
-----------------------
Email: fri@rsx42sun0.dofn.de
Phone: x49-7545-2256 (office), x49-7541-42305 (home)
Home address: D. Frieauff, Stockerholzstr. 27, 88048 Friedrichshafen, Germany


!!!! Important Notice !!!!
-----------------------------
- Klaus Liedl maintains an excellent WWW page about Linux on Compaq XL.
  It includes an FAQ, lots of tips & tricks as well as downloadable 
  boot disk images. The URL is: http://www-c724.uibk.ac.at/XL/
- Volunteer wanted for further maintenance of this driver software. I
  don't have the time anymore to do serious support as some of you will know.


Literature
----------
 - AMD AM53C974 PC-SCSI Technical Manual, publication #18624B
 - Amendment to the AMD AM53C974 PC-SCSI Technical Manual
 - AMD AM79C974 PC-NET Datasheet, publication #18681
 - Amendment to the AMD AM79C974 PC-NET Datasheet


THANKS to
---------
 - Drew Eckhardt, Robin Cutshaw, K. Liedl, Robert J. Pappas, A. Grenier, 
   Mark Stockton, David C. Niemi, Ben Craft, and many others who have helped