path: root/Documentation/scsi/ibmmca.txt

               -=< The IBM Microchannel SCSI-Subsystem >=-
	       
	                 for the IBM PS/2 series
		 
	  	   Low Level Software-Driver for Linux
		 
     Copyright (c) 1995 Strom Systems, Inc. under the terms of the GNU 
  General Public License. Originally written by Martin Kolinek, December 1995.
   Officially modified and maintained by Michael Lang since January 1999.
	   
 	                       Version 4.0a
	
   Last update: January 3, 2001
   
   Before you Start
   ----------------
   This is the common README.ibmmca file for all driver releases of the 
   IBM MCA SCSI driver for Linux. Please note, that driver releases 4.0
   or newer do not work with kernel versions older than 2.4.0, while driver
   versions older than 4.0 do not work with kernels 2.4.0 or later! If you
   try to compile your kernel with the wrong driver source, the 
   compilation is aborted and you get a corresponding error message. This is
   no bug in the driver. It prevents you from using the wrong sourcecode
   with the wrong kernel version.

   Authors of this Driver
   ----------------------
    - Chris Beauregard (improvement of the SCSI-device mapping by the driver)
    - Martin Kolinek (origin, first release of this driver)
    - Klaus Kudielka (multiple SCSI-host management/detection, adaption to
                      Linux Kernel 2.1.x, module support)
    - Michael Lang (assigning original pun/lun mapping, dynamical ldn
                    assignment, rewritten adapter detection, this file, 
		    patches, official driver maintenance and subsequent 
		    debugging, related with the driver)

   Table of Contents
   -----------------
   1 Abstract
   2 Driver Description
     2.1  IBM SCSI-Subsystem Detection
     2.2  Physical Units, Logical Units, and Logical Devices
     2.3  SCSI-Device Recognition and dynamical ldn Assignment
     2.4  SCSI-Device Order
     2.5  Regular SCSI-Command-Processing
     2.6  Abort & Reset Commands
     2.7  Disk Geometry
     2.8  Kernel Boot Option
     2.9  Driver Module Support
     2.10 Multiple Hostadapter Support
     2.11 /proc/scsi-Filesystem Information
     2.12 /proc/mca-Filesystem Information
     2.13 Supported IBM SCSI-Subsystems
     2.14 Linux Kernel Versions
   3 Code History
   4 To do
   5 Users' Manual
     5.1 Commandline Parameters
     5.2 Troubleshooting
     5.3 Bugreports
     5.4 Support WWW-page
   6 References
   7 Credits to
     7.1 People
     7.2 Sponsors & Supporters
   8 Trademarks
   9 Disclaimer

                              * * *

   1 Abstract
   ----------
   This README-file describes the IBM SCSI-subsystem low level driver for 
   Linux. The descriptions which were formerly kept in the source-code have 
   been taken out to this file to easify the codes' readability. The driver 
   description has been updated, as most of the former description was already
   quite outdated. The history of the driver development is also kept inside 
   here. Multiple historical developments have been summarized to shorten the 
   textsize a bit. At the end of this file you can find a small manual for 
   this driver and hints to get it running on your machine.

   2 Driver Description
   --------------------
   2.1 IBM SCSI-Subsystem Detection
   --------------------------------
   This is done in the ibmmca_detect() function. It first checks, if the
   Microchannel-bus support is enabled, as the IBM SCSI-subsystem needs the
   Microchannel. In a next step, a free interrupt is chosen and the main
   interrupt handler is connected to it to handle answers of the SCSI-
   subsystem(s). If the F/W SCSI-adapter is forced by the BIOS to use IRQ11
   instead of IRQ14, IRQ11 is used for the IBM SCSI-2 F/W adapter. In a 
   further step it is checked, if the adapter gets detected by force from
   the kernel commandline, where the I/O port and the SCSI-subsystem id can 
   be specified. The next step checks if there is an integrated SCSI-subsystem
   installed. This register area is fixed through all IBM PS/2 MCA-machines 
   and appears as something like a virtual slot 10 of the MCA-bus. On most
   PS/2 machines, the POS registers of slot 10 are set to 0xff or 0x00 if not
   integrated SCSI-controller is available. But on certain PS/2s, like model 
   9595, this slot 10 is used to store other information which at earlier
   stage confused the driver and resulted in the detection of some ghost-SCSI. 
   If POS-register 2 and 3 are not 0x00 and not 0xff, but all other POS
   registers are either 0xff or 0x00, there must be an integrated SCSI-
   subsystem present and it will be registered as IBM Integrated SCSI-
   Subsystem. The next step checks, if there is a slot-adapter installed on 
   the MCA-bus. To get this, the first two POS-registers, that represent the 
   adapter ID are checked. If they fit to one of the ids, stored in the 
   adapter list, a SCSI-subsystem is assumed to be found in a slot and will be 
   registered. This check is done through all possible MCA-bus slots to allow 
   more than one SCSI-adapter to be present in the PS/2-system and this is 
   already the first point of problems. Looking into the technical reference 
   manual for the IBM PS/2 common interfaces, the POS2 register must have 
   different interpretation of its single bits to avoid overlapping I/O
   regions. While one can assume, that the integrated subsystem has a fix 
   I/O-address at 0x3540 - 0x3547, further installed IBM SCSI-adapters must 
   use a different I/O-address. This is expressed by bit 1 to 3 of POS2 
   (multiplied by 8 + 0x3540). Bits 2 and 3 are reserved for the integrated 
   subsystem, but not for the adapters! The following list shows, how the 
   bits of POS2 and POS3 should be interpreted.
   
   The POS2-register of all PS/2 models' integrated SCSI-subsystems has the 
   following interpretation of bits:
                           Bit 7 - 4 : Chip Revision ID (Release)
                           Bit 3 - 2 : Reserved
                           Bit 1     : 8k NVRAM Disabled
                           Bit 0     : Chip Enable (EN-Signal)
   The POS3-register is interpreted as follows (for most IBM SCSI-subsys.):
                           Bit 7 - 5 : SCSI ID
                           Bit 4 - 0 : Reserved = 0
   The slot-adapters have different interpretation of these bits. The IBM SCSI
   adapter (w/Cache) and the IBM SCSI-2 F/W adapter use the following
   interpretation of the POS2 register:
                           Bit 7 - 4 : ROM Segment Address Select
			   Bit 3 - 1 : Adapter I/O Address Select (*8+0x3540)
			   Bit 0     : Adapter Enable (EN-Signal)
   and for the POS3 register:
                           Bit 7 - 5 : SCSI ID 
			   Bit 4     : Fairness Enable (SCSI ID3 f. F/W)
			   Bit 3 - 0 : Arbitration Level
   The most modern product of the series is the IBM SCSI-2 F/W adapter, it 
   allows dual-bus SCSI and SCSI-wide addressing, which means, PUNs may be
   between 0 and 15. Here, Bit 4 is the high-order bit of the 4-bit wide
   adapter PUN expression. In short words, this means, that IBM PS/2 machines 
   can only support 1 single integrated subsystem by default. Additional
   slot-adapters get ports assigned by the automatic configuration tool.

   One day I found a patch in ibmmca_detect(), forcing the I/O-address to be 
   0x3540 for integrated SCSI-subsystems, there was a remark placed, that on 
   integrated IBM SCSI-subsystems of model 56, the POS2 register was showing 5.
   This means, that really for these models, POS2 has to be interpreted
   sticking to the technical reference guide. In this case, the bit 2 (4) is 
   a reserved bit and may not be interpreted. These differences between the 
   adapters and the integrated controllers are taken into account by the 
   detection routine of the driver on from version >3.0g. 

   Every time, a SCSI-subsystem is discovered, the ibmmca_register() function
   is called. This function checks first, if the requested area for the I/O-
   address of this SCSI-subsystem is still available and assigns this I/O-
   area to the SCSI-subsystem. There are always 8 sequential I/O-addresses
   taken for each individual SCSI-subsystem found, which are:
   
     Offset            Type