scsi: docs: convert sym53c8xx_2.txt to ReST

Link: https://lore.kernel.org/r/08202c87294d61d147ec4ac784219d20805cdeb5.1583136624.git.mchehab+huawei@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 1209 insertions, 0 deletions

diff --git a/Documentation/scsi/sym53c8xx_2.rst b/Documentation/scsi/sym53c8xx_2.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================
+The Linux SYM-2 driver documentation file
+=========================================
+
+Written by Gerard Roudier <groudier@free.fr>
+
+21 Rue Carnot
+
+95170 DEUIL LA BARRE - FRANCE
+
+Updated by Matthew Wilcox <matthew@wil.cx>
+
+2004-10-09
+
+.. Contents
+
+   1.  Introduction
+   2.  Supported chips and SCSI features
+   3.  Advantages of this driver for newer chips.
+         3.1 Optimized SCSI SCRIPTS
+         3.2 New features appeared with the SYM53C896
+   4.  Memory mapped I/O versus normal I/O
+   5.  Tagged command queueing
+   6.  Parity checking
+   7.  Profiling information
+   8.  Control commands
+         8.1  Set minimum synchronous period
+         8.2  Set wide size
+         8.3  Set maximum number of concurrent tagged commands
+         8.4  Set debug mode
+         8.5  Set flag (no_disc)
+         8.6  Set verbose level
+         8.7  Reset all logical units of a target
+         8.8  Abort all tasks of all logical units of a target
+   9.  Configuration parameters
+   10. Boot setup commands
+         10.1 Syntax
+         10.2 Available arguments
+                10.2.1  Default number of tagged commands
+                10.2.2  Burst max
+                10.2.3  LED support
+                10.2.4  Differential mode
+                10.2.5  IRQ mode
+                10.2.6  Check SCSI BUS
+                10.2.7  Suggest a default SCSI id for hosts
+                10.2.8  Verbosity level
+                10.2.9  Debug mode
+                10.2.10 Settle delay
+                10.2.11 Serial NVRAM
+                10.2.12 Exclude a host from being attached
+         10.3 Converting from old options
+         10.4 SCSI BUS checking boot option
+   11. SCSI problem troubleshooting
+         15.1 Problem tracking
+         15.2 Understanding hardware error reports
+   12. Serial NVRAM support (by Richard Waltham)
+         17.1 Features
+         17.2 Symbios NVRAM layout
+         17.3 Tekram  NVRAM layout
+
+
+1. Introduction
+===============
+
+This driver supports the whole SYM53C8XX family of PCI-SCSI controllers.
+It also support the subset of LSI53C10XX PCI-SCSI controllers that are based
+on the SYM53C8XX SCRIPTS language.
+
+It replaces the sym53c8xx+ncr53c8xx driver bundle and shares its core code
+with the FreeBSD SYM-2 driver. The 'glue' that allows this driver to work
+under Linux is contained in 2 files named sym_glue.h and sym_glue.c.
+Other drivers files are intended not to depend on the Operating System
+on which the driver is used.
+
+The history of this driver can be summarized as follows:
+
+1993: ncr driver written for 386bsd and FreeBSD by:
+
+          - Wolfgang Stanglmeier        <wolf@cologne.de>
+          - Stefan Esser                <se@mi.Uni-Koeln.de>
+
+1996: port of the ncr driver to Linux-1.2.13 and rename it ncr53c8xx.
+
+          - Gerard Roudier
+
+1998: new sym53c8xx driver for Linux based on LOAD/STORE instruction and that
+      adds full support for the 896 but drops support for early NCR devices.
+
+          - Gerard Roudier
+
+1999: port of the sym53c8xx driver to FreeBSD and support for the LSI53C1010
+      33 MHz and 66MHz Ultra-3 controllers. The new driver is named 'sym'.
+
+          - Gerard Roudier
+
+2000: Add support for early NCR devices to FreeBSD 'sym' driver.
+      Break the driver into several sources and separate the OS glue
+      code from the core code that can be shared among different O/Ses.
+      Write a glue code for Linux.
+
+          - Gerard Roudier
+
+2004: Remove FreeBSD compatibility code.  Remove support for versions of
+      Linux before 2.6.  Start using Linux facilities.
+
+This README file addresses the Linux version of the driver. Under FreeBSD,
+the driver documentation is the sym.8 man page.
+
+Information about new chips is available at LSILOGIC web server:
+
+          http://www.lsilogic.com/
+
+SCSI standard documentations are available at T10 site:
+
+          http://www.t10.org/
+
+Useful SCSI tools written by Eric Youngdale are part of most Linux
+distributions:
+
+   ============ ==========================
+   scsiinfo     command line tool
+   scsi-config  TCL/Tk tool using scsiinfo
+   ============ ==========================
+
+2. Supported chips and SCSI features
+====================================
+
+The following features are supported for all chips:
+
+	- Synchronous negotiation
+	- Disconnection
+	- Tagged command queuing
+	- SCSI parity checking
+	- PCI Master parity checking
+
+Other features depends on chip capabilities.
+
+The driver notably uses optimized SCRIPTS for devices that support
+LOAD/STORE and handles PHASE MISMATCH from SCRIPTS for devices that
+support the corresponding feature.
+
+The following table shows some characteristics of the chip family.
+
++--------+-----------+-----+-----------+------------+------------+---------+
+|        |           |     |           |            |Load/store  |Hardware |
+|        |On board   |     |           |            |scripts     |phase    |
+|Chip    |SDMS BIOS  |Wide |SCSI std.  | Max. sync  |            |mismatch |
++--------+-----------+-----+-----------+------------+------------+---------+
+|810     |     N     |  N  | FAST10    | 10 MB/s    |      N     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|810A    |     N     |  N  | FAST10    | 10 MB/s    |      Y     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|815     |     Y     |  N  | FAST10    | 10 MB/s    |      N     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|825     |     Y     |  Y  | FAST10    | 20 MB/s    |      N     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|825A    |     Y     |  Y  | FAST10    | 20 MB/s    |      Y     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|860     |     N     |  N  | FAST20    | 20 MB/s    |      Y     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|875     |     Y     |  Y  | FAST20    | 40 MB/s    |      Y     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|875A    |     Y     |  Y  | FAST20    | 40 MB/s    |      Y     |    Y    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|876     |     Y     |  Y  | FAST20    | 40 MB/s    |      Y     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|895     |     Y     |  Y  | FAST40    | 80 MB/s    |      Y     |    N    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|895A    |     Y     |  Y  | FAST40    | 80 MB/s    |      Y     |    Y    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|896     |     Y     |  Y  | FAST40    | 80 MB/s    |      Y     |    Y    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|897     |     Y     |  Y  | FAST40    | 80 MB/s    |      Y     |    Y    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|1510D   |     Y     |  Y  | FAST40    | 80 MB/s    |      Y     |    Y    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|1010    |     Y     |  Y  | FAST80    |160 MB/s    |      Y     |    Y    |
++--------+-----------+-----+-----------+------------+------------+---------+
+|1010_66 |     Y     |  Y  | FAST80    |160 MB/s    |      Y     |    Y    |
+|[1]_    |           |     |           |            |            |         |
++--------+-----------+-----+-----------+------------+------------+---------+
+
+.. [1] Chip supports 33MHz and 66MHz PCI bus clock.
+
+
+Summary of other supported features:
+
+:Module:                allow to load the driver
+:Memory mapped I/O:     increases performance
+:Control commands:      write operations to the proc SCSI file system
+:Debugging information: written to syslog (expert only)
+:Serial NVRAM:          Symbios and Tekram formats
+
+- Scatter / gather
+- Shared interrupt
+- Boot setup commands
+
+
+3. Advantages of this driver for newer chips.
+=============================================
+
+3.1 Optimized SCSI SCRIPTS
+--------------------------
+
+All chips except the 810, 815 and 825, support new SCSI SCRIPTS instructions
+named LOAD and STORE that allow to move up to 1 DWORD from/to an IO register
+to/from memory much faster that the MOVE MEMORY instruction that is supported
+by the 53c7xx and 53c8xx family.
+
+The LOAD/STORE instructions support absolute and DSA relative addressing
+modes. The SCSI SCRIPTS had been entirely rewritten using LOAD/STORE instead
+of MOVE MEMORY instructions.
+
+Due to the lack of LOAD/STORE SCRIPTS instructions by earlier chips, this
+driver also incorporates a different SCRIPTS set based on MEMORY MOVE, in
+order to provide support for the entire SYM53C8XX chips family.
+
+3.2 New features appeared with the SYM53C896
+--------------------------------------------
+
+Newer chips (see above) allows handling of the phase mismatch context from
+SCRIPTS (avoids the phase mismatch interrupt that stops the SCSI processor
+until the C code has saved the context of the transfer).
+
+The 896 and 1010 chips support 64 bit PCI transactions and addressing,
+while the 895A supports 32 bit PCI transactions and 64 bit addressing.
+The SCRIPTS processor of these chips is not true 64 bit, but uses segment
+registers for bit 32-63. Another interesting feature is that LOAD/STORE
+instructions that address the on-chip RAM (8k) remain internal to the chip.
+
+4. Memory mapped I/O versus normal I/O
+======================================
+
+Memory mapped I/O has less latency than normal I/O and is the recommended
+way for doing IO with PCI devices. Memory mapped I/O seems to work fine on
+most hardware configurations, but some poorly designed chipsets may break
+this feature. A configuration option is provided for normal I/O to be
+used but the driver defaults to MMIO.
+
+5. Tagged command queueing
+==========================
+
+Queuing more than 1 command at a time to a device allows it to perform
+optimizations based on actual head positions and its mechanical
+characteristics. This feature may also reduce average command latency.
+In order to really gain advantage of this feature, devices must have
+a reasonable cache size (No miracle is to be expected for a low-end
+hard disk with 128 KB or less).
+
+Some known old SCSI devices do not properly support tagged command queuing.
+Generally, firmware revisions that fix this kind of problems are available
+at respective vendor web/ftp sites.
+
+All I can say is that I never have had problem with tagged queuing using
+this driver and its predecessors. Hard disks that behaved correctly for
+me using tagged commands are the following:
+
+- IBM S12 0662
+- Conner 1080S
+- Quantum Atlas I
+- Quantum Atlas II
+- Seagate Cheetah I
+- Quantum Viking II
+- IBM DRVS
+- Quantum Atlas IV
+- Seagate Cheetah II
+
+If your controller has NVRAM, you can configure this feature per target
+from the user setup tool. The Tekram Setup program allows to tune the
+maximum number of queued commands up to 32. The Symbios Setup only allows
+to enable or disable this feature.
+
+The maximum number of simultaneous tagged commands queued to a device
+is currently set to 16 by default.  This value is suitable for most SCSI
+disks.  With large SCSI disks (>= 2GB, cache >= 512KB, average seek time
+<= 10 ms), using a larger value may give better performances.
+
+This driver supports up to 255 commands per device, and but using more than
+64 is generally not worth-while, unless you are using a very large disk or
+disk arrays. It is noticeable that most of recent hard disks seem not to
+accept more than 64 simultaneous commands. So, using more than 64 queued
+commands is probably just resource wasting.
+
+If your controller does not have NVRAM or if it is managed by the SDMS
+BIOS/SETUP, you can configure tagged queueing feature and device queue
+depths from the boot command-line. For example::
+
+  sym53c8xx=tags:4/t2t3q15-t4q7/t1u0q32
+
+will set tagged commands queue depths as follow:
+
+- target 2  all luns  on controller 0 --> 15
+- target 3  all luns  on controller 0 --> 15
+- target 4  all luns  on controller 0 -->  7
+- target 1  lun 0     on controller 1 --> 32
+- all other target/lun                -->  4
+
+In some special conditions, some SCSI disk firmwares may return a
+QUEUE FULL status for a SCSI command. This behaviour is managed by the
+driver using the following heuristic:
+
+- Each time a QUEUE FULL status is returned, tagged queue depth is reduced
+  to the actual number of disconnected commands.
+
+- Every 200 successfully completed SCSI commands, if allowed by the
+  current limit, the maximum number of queueable commands is incremented.
+
+Since QUEUE FULL status reception and handling is resource wasting, the
+driver notifies by default this problem to user by indicating the actual
+number of commands used and their status, as well as its decision on the
+device queue depth change.
+The heuristic used by the driver in handling QUEUE FULL ensures that the
+impact on performances is not too bad. You can get rid of the messages by
+setting verbose level to zero, as follow:
+
+1st method:
+	    boot your system using 'sym53c8xx=verb:0' option.
+2nd method:
+	    apply "setverbose 0" control command to the proc fs entry
+            corresponding to your controller after boot-up.
+
+6. Parity checking
+==================
+
+The driver supports SCSI parity checking and PCI bus master parity
+checking.  These features must be enabled in order to ensure safe
+data transfers.  Some flawed devices or mother boards may have problems
+with parity.  The options to defeat parity checking have been removed
+from the driver.
+
+7. Profiling information
+========================
+
+This driver does not provide profiling information as did its predecessors.
+This feature was not this useful and added complexity to the code.
+As the driver code got more complex, I have decided to remove everything
+that didn't seem actually useful.
+
+8. Control commands
+===================
+
+Control commands can be sent to the driver with write operations to
+the proc SCSI file system. The generic command syntax is the
+following::
+
+      echo "<verb> <parameters>" >/proc/scsi/sym53c8xx/0
+      (assumes controller number is 0)
+
+Using "all" for "<target>" parameter with the commands below will
+apply to all targets of the SCSI chain (except the controller).
+
+Available commands:
+
+8.1 Set minimum synchronous period factor
+-----------------------------------------
+
+    setsync <target> <period factor>
+
+    :target:   target number
+    :period:   minimum synchronous period.
+               Maximum speed = 1000/(4*period factor) except for special
+               cases below.
+
+    Specify a period of 0, to force asynchronous transfer mode.
+
+     -  9 means 12.5 nano-seconds synchronous period
+     - 10 means 25 nano-seconds synchronous period
+     - 11 means 30 nano-seconds synchronous period
+     - 12 means 50 nano-seconds synchronous period
+
+8.2 Set wide size
+-----------------
+
+    setwide <target> <size>
+
+    :target:   target number
+    :size:     0=8 bits, 1=16bits
+
+8.3 Set maximum number of concurrent tagged commands
+----------------------------------------------------
+
+    settags <target> <tags>
+
+    :target:   target number
+    :tags:     number of concurrent tagged commands
+               must not be greater than configured (default: 16)
+
+8.4 Set debug mode
+------------------
+
+    setdebug <list of debug flags>
+
+    Available debug flags:
+
+	======== ========================================================
+        alloc    print info about memory allocations (ccb, lcb)
+        queue    print info about insertions into the command start queue
+        result   print sense data on CHECK CONDITION status
+        scatter  print info about the scatter process
+        scripts  print info about the script binding process
+	tiny     print minimal debugging information
+	timing   print timing information of the NCR chip
+	nego     print information about SCSI negotiations
+	phase    print information on script interruptions
+	======== ========================================================
+
+    Use "setdebug" with no argument to reset debug flags.
+
+
+8.5 Set flag (no_disc)
+----------------------
+
+    setflag <target> <flag>
+
+    :target:    target number
+
+    For the moment, only one flag is available:
+
+        no_disc:   not allow target to disconnect.
+
+    Do not specify any flag in order to reset the flag. For example:
+
+    setflag 4
+      will reset no_disc flag for target 4, so will allow it disconnections.
+    setflag all
+      will allow disconnection for all devices on the SCSI bus.
+
+
+8.6 Set verbose level
+---------------------
+
+    setverbose #level
+
+    The driver default verbose level is 1. This command allows to change
+    th driver verbose level after boot-up.
+
+8.7 Reset all logical units of a target
+---------------------------------------
+
+    resetdev <target>
+
+    :target:    target number
+
+    The driver will try to send a BUS DEVICE RESET message to the target.
+
+8.8 Abort all tasks of all logical units of a target
+----------------------------------------------------
+
+    cleardev <target>
+
+    :target:    target number
+
+    The driver will try to send a ABORT message to all the logical units
+    of the target.
+
+
+9. Configuration parameters
+===========================
+
+Under kernel configuration tools (make menuconfig, for example), it is
+possible to change some default driver configuration parameters.
+If the firmware of all your devices is perfect enough, all the
+features supported by the driver can be enabled at start-up. However,
+if only one has a flaw for some SCSI feature, you can disable the
+support by the driver of this feature at linux start-up and enable
+this feature after boot-up only for devices that support it safely.
+
+Configuration parameters:
+
+Use normal IO                         (default answer: n)
+    Answer "y" if you suspect your mother board to not allow memory mapped I/O.
+    May slow down performance a little.
+
+Default tagged command queue depth    (default answer: 16)
+    Entering 0 defaults to tagged commands not being used.
+    This parameter can be specified from the boot command line.
+
+Maximum number of queued commands     (default answer: 32)
+    This option allows you to specify the maximum number of tagged commands
+    that can be queued to a device. The maximum supported value is 255.
+
+Synchronous transfers frequency       (default answer: 80)
+    This option allows you to specify the frequency in MHz the driver
+    will use at boot time for synchronous data transfer negotiations.
+    0 means "asynchronous data transfers".
+
+10. Boot setup commands
+=======================
+
+10.1 Syntax
+-----------
+
+Setup commands can be passed to the driver either at boot time or as
+parameters to modprobe, as described in Documentation/admin-guide/kernel-parameters.rst
+
+Example of boot setup command under lilo prompt::
+
+    lilo: linux root=/dev/sda2 sym53c8xx.cmd_per_lun=4 sym53c8xx.sync=10 sym53c8xx.debug=0x200
+
+- enable tagged commands, up to 4 tagged commands queued.
+- set synchronous negotiation speed to 10 Mega-transfers / second.
+- set DEBUG_NEGO flag.
+
+The following command will install the driver module with the same
+options as above::
+
+    modprobe sym53c8xx cmd_per_lun=4 sync=10 debug=0x200
+
+10.2 Available arguments
+------------------------
+
+10.2.1  Default number of tagged commands
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+        - cmd_per_lun=0 (or cmd_per_lun=1) tagged command queuing disabled
+        - cmd_per_lun=#tags (#tags > 1) tagged command queuing enabled
+
+  #tags will be truncated to the max queued commands configuration parameter.
+
+10.2.2 Burst max
+^^^^^^^^^^^^^^^^
+
+	========== ======================================================
+        burst=0    burst disabled
+        burst=255  get burst length from initial IO register settings.
+        burst=#x   burst enabled (1<<#x burst transfers max)
+
+		   #x is an integer value which is log base 2 of the burst
+		   transfers max.
+	========== ======================================================
+
+  By default the driver uses the maximum value supported by the chip.
+
+10.2.3 LED support
+^^^^^^^^^^^^^^^^^^
+
+	=====      ===================
+        led=1      enable  LED support
+        led=0      disable LED support
+	=====      ===================
+
+  Do not enable LED support if your scsi board does not use SDMS BIOS.
+  (See 'Configuration parameters')
+
+10.2.4 Differential mode
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+	======	=================================
+	diff=0	never set up diff mode
+        diff=1	set up diff mode if BIOS set it
+        diff=2	always set up diff mode
+        diff=3	set diff mode if GPIO3 is not set
+	======	=================================
+
+10.2.5 IRQ mode
+^^^^^^^^^^^^^^^
+
+	======     ================================================
+        irqm=0     always open drain
+        irqm=1     same as initial settings (assumed BIOS settings)
+        irqm=2     always totem pole
+	======     ================================================
+
+10.2.6 Check SCSI BUS
+^^^^^^^^^^^^^^^^^^^^^
+
+        buschk=<option bits>
+
+    Available option bits:
+
+	===    ================================================
+        0x0    No check.
+        0x1    Check and do not attach the controller on error.
+        0x2    Check and just warn on error.
+	===    ================================================
+
+10.2.7 Suggest a default SCSI id for hosts
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+	==========	==========================================
+        hostid=255	no id suggested.
+        hostid=#x	(0 < x < 7) x suggested for hosts SCSI id.
+	==========	==========================================
+
+    If a host SCSI id is available from the NVRAM, the driver will ignore
+    any value suggested as boot option. Otherwise, if a suggested value
+    different from 255 has been supplied, it will use it. Otherwise, it will
+    try to deduce the value previously set in the hardware and use value
+    7 if the hardware value is zero.
+
+10.2.8  Verbosity level
+^^^^^^^^^^^^^^^^^^^^^^^
+
+	======     ========
+        verb=0     minimal
+        verb=1     normal
+        verb=2     too much
+	======     ========
+
+10.2.9 Debug mode
+^^^^^^^^^^^^^^^^^
+
+	=========   ====================================
+        debug=0	    clear debug flags
+        debug=#x    set debug flags
+
+		    #x is an integer value combining the
+		    following power-of-2 values:
+
+		    =============  ======
+		    DEBUG_ALLOC       0x1
+		    DEBUG_PHASE       0x2
+		    DEBUG_POLL        0x4
+		    DEBUG_QUEUE       0x8
+		    DEBUG_RESULT     0x10
+		    DEBUG_SCATTER    0x20
+		    DEBUG_SCRIPT     0x40
+		    DEBUG_TINY       0x80
+		    DEBUG_TIMING    0x100
+		    DEBUG_NEGO      0x200
+		    DEBUG_TAGS      0x400
+		    DEBUG_FREEZE    0x800
+		    DEBUG_RESTART  0x1000
+		    =============  ======
+	=========   ====================================
+
+  You can play safely with DEBUG_NEGO. However, some of these flags may
+  generate bunches of syslog messages.
+
+10.2.10 Settle delay
+^^^^^^^^^^^^^^^^^^^^
+
+	========	===================
+        settle=n	delay for n seconds
+	========	===================
+
+  After a bus reset, the driver will delay for n seconds before talking
+  to any device on the bus.  The default is 3 seconds and safe mode will
+  default it to 10.
+
+10.2.11 Serial NVRAM
+^^^^^^^^^^^^^^^^^^^^
+
+	.. Note:: option not currently implemented.
+
+	=======     =========================================
+        nvram=n     do not look for serial NVRAM
+        nvram=y     test controllers for onboard serial NVRAM
+	=======     =========================================
+
+        (alternate binary form)
+
+        nvram=<bits options>
+
+        ====   =================================================================
+        0x01   look for NVRAM  (equivalent to nvram=y)
+        0x02   ignore NVRAM "Synchronous negotiation" parameters for all devices
+        0x04   ignore NVRAM "Wide negotiation"  parameter for all devices
+        0x08   ignore NVRAM "Scan at boot time" parameter for all devices
+        0x80   also attach controllers set to OFF in the NVRAM (sym53c8xx only)
+        ====   =================================================================
+
+10.2.12 Exclude a host from being attached
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+        excl=<io_address>,...
+
+    Prevent host at a given io address from being attached.
+    For example 'excl=0xb400,0xc000' indicate to the
+    driver not to attach hosts at address 0xb400 and 0xc000.
+
+10.3 Converting from old style options
+--------------------------------------
+
+Previously, the sym2 driver accepted arguments of the form::
+
+	sym53c8xx=tags:4,sync:10,debug:0x200
+
+As a result of the new module parameters, this is no longer available.
+Most of the options have remained the same, but tags has become
+cmd_per_lun to reflect its different purposes.  The sample above would
+be specified as::
+
+	modprobe sym53c8xx cmd_per_lun=4 sync=10 debug=0x200
+
+or on the kernel boot line as::
+
+	sym53c8xx.cmd_per_lun=4 sym53c8xx.sync=10 sym53c8xx.debug=0x200
+
+10.4 SCSI BUS checking boot option
+----------------------------------
+
+When this option is set to a non-zero value, the driver checks SCSI lines
+logic state, 100 micro-seconds after having asserted the SCSI RESET line.
+The driver just reads SCSI lines and checks all lines read FALSE except RESET.
+Since SCSI devices shall release the BUS at most 800 nano-seconds after SCSI
+RESET has been asserted, any signal to TRUE may indicate a SCSI BUS problem.
+Unfortunately, the following common SCSI BUS problems are not detected:
+
+- Only 1 terminator installed.
+- Misplaced terminators.
+- Bad quality terminators.
+
+On the other hand, either bad cabling, broken devices, not conformant
+devices, ... may cause a SCSI signal to be wrong when te driver reads it.
+
+15. SCSI problem troubleshooting
+================================
+
+15.1 Problem tracking
+---------------------
+
+Most SCSI problems are due to a non conformant SCSI bus or too buggy
+devices.  If unfortunately you have SCSI problems, you can check the
+following things:
+
+- SCSI bus cables
+- terminations at both end of the SCSI chain
+- linux syslog messages (some of them may help you)
+
+If you do not find the source of problems, you can configure the
+driver or devices in the NVRAM with minimal features.
+
+- only asynchronous data transfers
+- tagged commands disabled
+- disconnections not allowed
+
+Now, if your SCSI bus is ok, your system has every chance to work
+with this safe configuration but performances will not be optimal.
+
+If it still fails, then you can send your problem description to
+appropriate mailing lists or news-groups.  Send me a copy in order to
+be sure I will receive it.  Obviously, a bug in the driver code is
+possible.
+
+  My current email address: Gerard Roudier <groudier@free.fr>
+
+Allowing disconnections is important if you use several devices on
+your SCSI bus but often causes problems with buggy devices.
+Synchronous data transfers increases throughput of fast devices like
+hard disks.  Good SCSI hard disks with a large cache gain advantage of
+tagged commands queuing.
+
+15.2 Understanding hardware error reports
+-----------------------------------------
+
+When the driver detects an unexpected error condition, it may display a
+message of the following pattern::
+
+    sym0:1: ERROR (0:48) (1-21-65) (f/95/0) @ (script 7c0:19000000).
+    sym0: script cmd = 19000000
+    sym0: regdump: da 10 80 95 47 0f 01 07 75 01 81 21 80 01 09 00.
+
+Some fields in such a message may help you understand the cause of the
+problem, as follows::
+
+    sym0:1: ERROR (0:48) (1-21-65) (f/95/0) @ (script 7c0:19000000).
+    .....A.........B.C....D.E..F....G.H..I.......J.....K...L.......
+
+Field A : target number.
+  SCSI ID of the device the controller was talking with at the moment the
+  error occurs.
+
+Field B : DSTAT io register (DMA STATUS)
+  ========   =============================================================
+  Bit 0x40   MDPE Master Data Parity Error
+             Data parity error detected on the PCI BUS.
+  Bit 0x20   BF   Bus Fault
+             PCI bus fault condition detected
+  Bit 0x01   IID  Illegal Instruction Detected
+             Set by the chip when it detects an Illegal Instruction format
+             on some condition that makes an instruction illegal.
+  Bit 0x80   DFE Dma Fifo Empty
+             Pure status bit that does not indicate an error.
+  ========   =============================================================
+
+  If the reported DSTAT value contains a combination of MDPE (0x40),
+  BF (0x20), then the cause may be likely due to a PCI BUS problem.
+
+Field C : SIST io register (SCSI Interrupt Status)
+  ========   ==================================================================
+  Bit 0x08   SGE  SCSI GROSS ERROR
+             Indicates that the chip detected a severe error condition
+             on the SCSI BUS that prevents the SCSI protocol from functioning
+             properly.
+  Bit 0x04   UDC  Unexpected Disconnection
+             Indicates that the device released the SCSI BUS when the chip
+             was not expecting this to happen. A device may behave so to
+             indicate the SCSI initiator that an error condition not reportable              using the SCSI protocol has occurred.
+  Bit 0x02   RST  SCSI BUS Reset
+             Generally SCSI targets do not reset the SCSI BUS, although any
+             device on the BUS can reset it at any time.
+  Bit 0x01   PAR  Parity
+             SCSI parity error detected.
+  ========   ==================================================================
+
+  On a faulty SCSI BUS, any error condition among SGE (0x08), UDC (0x04) and
+  PAR (0x01) may be detected by the chip. If your SCSI system sometimes
+  encounters such error conditions, especially SCSI GROSS ERROR, then a SCSI
+  BUS problem is likely the cause of these errors.
+
+For fields D,E,F,G and H, you may look into the sym53c8xx_defs.h file
+that contains some minimal comments on IO register bits.
+
+Field D : SOCL  Scsi Output Control Latch
+          This register reflects the state of the SCSI control lines the
+          chip want to drive or compare against.
+Field E : SBCL  Scsi Bus Control Lines
+          Actual value of control lines on the SCSI BUS.
+Field F : SBDL  Scsi Bus Data Lines
+          Actual value of data lines on the SCSI BUS.
+Field G : SXFER  SCSI Transfer
+          Contains the setting of the Synchronous Period for output and
+          the current Synchronous offset (offset 0 means asynchronous).
+Field H : SCNTL3 Scsi Control Register 3
+          Contains the setting of timing values for both asynchronous and
+          synchronous data transfers.
+Field I : SCNTL4 Scsi Control Register 4
+          Only meaningful for 53C1010 Ultra3 controllers.
+
+Understanding Fields J, K, L and dumps requires to have good knowledge of
+SCSI standards, chip cores functionnals and internal driver data structures.
+You are not required to decode and understand them, unless you want to help
+maintain the driver code.
+
+17. Serial NVRAM (added by Richard Waltham: dormouse@farsrobt.demon.co.uk)
+==========================================================================
+
+17.1 Features
+-------------
+
+Enabling serial NVRAM support enables detection of the serial NVRAM included
+on Symbios and some Symbios compatible host adaptors, and Tekram boards. The
+serial NVRAM is used by Symbios and Tekram to hold set up parameters for the
+host adaptor and its attached drives.
+
+The Symbios NVRAM also holds data on the boot order of host adaptors in a
+system with more than one host adaptor.  This information is no longer used
+as it's fundamentally incompatible with the hotplug PCI model.
+
+Tekram boards using Symbios chips, DC390W/F/U, which have NVRAM are detected
+and this is used to distinguish between Symbios compatible and Tekram host
+adaptors. This is used to disable the Symbios compatible "diff" setting
+incorrectly set on Tekram boards if the CONFIG_SCSI_53C8XX_SYMBIOS_COMPAT
+configuration parameter is set enabling both Symbios and Tekram boards to be
+used together with the Symbios cards using all their features, including
+"diff" support. ("led pin" support for Symbios compatible cards can remain
+enabled when using Tekram cards. It does nothing useful for Tekram host
+adaptors but does not cause problems either.)
+
+The parameters the driver is able to get from the NVRAM depend on the
+data format used, as follow:
+
++-------------------------------+------------------+--------------+
+|                               |Tekram format     |Symbios format|
++-------------------------------+------------------+--------------+
+|General and host parameters    |                  |              |
++-------------------------------+------------------+--------------+
+|  * Boot order                 |        N         |       Y      |
++-------------------------------+------------------+--------------+
+|  * Host SCSI ID               |        Y         |       Y      |
++-------------------------------+------------------+--------------+
+|  * SCSI parity checking       |        Y         |       Y      |
++-------------------------------+------------------+--------------+
+|  * Verbose boot messages      |        N         |       Y      |
++-------------------------------+------------------+--------------+
+|SCSI devices parameters                                          |
++-------------------------------+------------------+--------------+
+|  * Synchronous transfer speed |        Y         |       Y      |
++-------------------------------+------------------+--------------+
+|  * Wide 16 / Narrow           |        Y         |       Y      |
++-------------------------------+------------------+--------------+
+|  * Tagged Command Queuing     |        Y         |       Y      |
+|    enabled                    |                  |              |
++-------------------------------+------------------+--------------+
+|  * Disconnections enabled     |        Y         |       Y      |
++-------------------------------+------------------+--------------+
+|  * Scan at boot time          |        N         |       Y      |
++-------------------------------+------------------+--------------+
+
+
+In order to speed up the system boot, for each device configured without
+the "scan at boot time" option, the driver forces an error on the
+first TEST UNIT READY command received for this device.
+
+
+17.2 Symbios NVRAM layout
+-------------------------
+
+typical data at NVRAM address 0x100 (53c810a NVRAM)::
+
+    00 00
+    64 01
+    8e 0b
+
+    00 30 00 00 00 00 07 00 00 00 00 00 00 00 07 04 10 04 00 00
+
+    04 00 0f 00 00 10 00 50 00 00 01 00 00 62
+    04 00 03 00 00 10 00 58 00 00 01 00 00 63
+    04 00 01 00 00 10 00 48 00 00 01 00 00 61
+    00 00 00 00 00 00 00 00 00 00 00 00 00 00
+
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+    00 00 00 00 00 00 00 00
+
+    fe fe
+    00 00
+    00 00
+
+NVRAM layout details
+
+============= =================
+NVRAM Address
+============= =================
+0x000-0x0ff   not used
+0x100-0x26f   initialised data
+0x270-0x7ff   not used
+============= =================
+
+general layout::
+
+        header  -   6 bytes,
+        data    - 356 bytes (checksum is byte sum of this data)
+        trailer -   6 bytes
+                  ---
+        total     368 bytes
+
+data area layout::
+
+        controller set up  -  20 bytes
+        boot configuration -  56 bytes (4x14 bytes)
+        device set up      - 128 bytes (16x8 bytes)
+        unused (spare?)    - 152 bytes (19x8 bytes)
+                             ---
+        total                356 bytes
+
+header::
+
+    00 00   - ?? start marker
+    64 01   - byte count (lsb/msb excludes header/trailer)
+    8e 0b   - checksum (lsb/msb excludes header/trailer)
+
+controller set up::
+
+    00 30 00 00 00 00 07 00 00 00 00 00 00 00 07 04 10 04 00 00
+		    |     |           |     |
+		    |     |           |      -- host ID
+		    |     |           |
+		    |     |            --Removable Media Support
+		    |     |               0x00 = none
+		    |     |               0x01 = Bootable Device
+		    |     |               0x02 = All with Media
+		    |     |
+		    |      --flag bits 2
+		    |        0x00000001= scan order hi->low
+		    |            (default 0x00 - scan low->hi)
+			--flag bits 1
+			0x00000001 scam enable
+			0x00000010 parity enable
+			0x00000100 verbose boot msgs
+
+remaining bytes unknown - they do not appear to change in my
+current set up for any of the controllers.
+
+default set up is identical for 53c810a and 53c875 NVRAM
+(Removable Media added Symbios BIOS version 4.09)
+
+boot configuration
+
+boot order set by order of the devices in this table::
+
+    04 00 0f 00 00 10 00 50 00 00 01 00 00 62 -- 1st controller
+    04 00 03 00 00 10 00 58 00 00 01 00 00 63    2nd controller
+    04 00 01 00 00 10 00 48 00 00 01 00 00 61    3rd controller
+    00 00 00 00 00 00 00 00 00 00 00 00 00 00    4th controller
+	|  |  |  |     |        |     |  |
+	|  |  |  |     |        |      ---- PCI io port adr
+	|  |  |  |     |         --0x01 init/scan at boot time
+	|  |  |  |      --PCI device/function number (0xdddddfff)
+	|  |   ----- ?? PCI vendor ID (lsb/msb)
+	    ----PCI device ID (lsb/msb)
+
+?? use of this data is a guess but seems reasonable
+
+remaining bytes unknown - they do not appear to change in my
+current set up
+
+default set up is identical for 53c810a and 53c875 NVRAM
+
+device set up (up to 16 devices - includes controller)::
+
+    0f 00 08 08 64 00 0a 00 - id 0
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00
+    0f 00 08 08 64 00 0a 00 - id 15
+    |     |  |  |     |  |
+    |     |  |  |      ----timeout (lsb/msb)
+    |     |  |   --synch period (0x?? 40 Mtrans/sec- fast 40) (probably 0x28)
+    |     |  |                  (0x30 20 Mtrans/sec- fast 20)
+    |     |  |                  (0x64 10 Mtrans/sec- fast )
+    |     |  |                  (0xc8  5 Mtrans/sec)
+    |     |  |                  (0x00  asynchronous)
+    |     |   -- ?? max sync offset (0x08 in NVRAM on 53c810a)
+    |     |                         (0x10 in NVRAM on 53c875)
+    |      --device bus width (0x08 narrow)
+    |                         (0x10 16 bit wide)
+    --flag bits
+	0x00000001 - disconnect enabled
+	0x00000010 - scan at boot time
+	0x00000100 - scan luns
+	0x00001000 - queue tags enabled
+
+remaining bytes unknown - they do not appear to change in my
+current set up
+
+?? use of this data is a guess but seems reasonable
+(but it could be max bus width)
+
+default set up for 53c810a NVRAM
+default set up for 53c875 NVRAM
+
+				- bus width     - 0x10
+                                - sync offset ? - 0x10
+                                - sync period   - 0x30
+
+?? spare device space (32 bit bus ??)::
+
+    00 00 00 00 00 00 00 00  (19x8bytes)
+    .
+    .
+    00 00 00 00 00 00 00 00
+
+default set up is identical for 53c810a and 53c875 NVRAM
+
+trailer::
+
+    fe fe   - ? end marker ?
+    00 00
+    00 00
+
+default set up is identical for 53c810a and 53c875 NVRAM
+
+17.3 Tekram NVRAM layout
+------------------------
+
+nvram 64x16 (1024 bit)
+
+Drive settings::
+
+    Drive ID 0-15 (addr 0x0yyyy0 = device setup, yyyy = ID)
+		(addr 0x0yyyy1 = 0x0000)
+
+	x x x x  x x x x  x x x x  x x x x
+		| | |      | |  | | | |
+		| | |      | |  | | |  ----- parity check   0 - off
+		| | |      | |  | | |                       1 - on
+		| | |      | |  | | |
+		| | |      | |  | |  ------- sync neg       0 - off
+		| | |      | |  | |                         1 - on
+		| | |      | |  | |
+		| | |      | |  |  --------- disconnect     0 - off
+		| | |      | |  |                           1 - on
+		| | |      | |  |
+		| | |      | |   ----------- start cmd      0 - off
+		| | |      | |                              1 - on
+		| | |      | |
+		| | |      |  -------------- tagged cmds    0 - off
+		| | |      |                                1 - on
+		| | |      |
+		| | |       ---------------- wide neg       0 - off
+		| | |                                       1 - on
+		| | |
+		    --------------------------- sync rate      0 - 10.0 Mtrans/sec
+							    1 -  8.0
+							    2 -  6.6
+							    3 -  5.7
+							    4 -  5.0
+							    5 -  4.0
+							    6 -  3.0
+							    7 -  2.0
+							    7 -  2.0
+							    8 - 20.0
+							    9 - 16.7
+							    a - 13.9
+							    b - 11.9
+
+Global settings
+
+Host flags 0 (addr 0x100000, 32)::
+
+    x x x x  x x x x  x x x x  x x x x
+    | | | |  | | | |           | | | |
+    | | | |  | | | |            ----------- host ID    0x00 - 0x0f
+    | | | |  | | | |
+    | | | |  | | |  ----------------------- support for    0 - off
+    | | | |  | | |                          > 2 drives     1 - on
+    | | | |  | | |
+    | | | |  | |  ------------------------- support drives 0 - off
+    | | | |  | |                            > 1Gbytes      1 - on
+    | | | |  | |
+    | | | |  |  --------------------------- bus reset on   0 - off
+    | | | |  |                                power on     1 - on
+    | | | |  |
+    | | | |   ----------------------------- active neg     0 - off
+    | | | |                                                1 - on
+    | | | |
+    | | |  -------------------------------- imm seek       0 - off
+    | | |                                                  1 - on
+    | | |
+    | |  ---------------------------------- scan luns      0 - off
+    | |                                                    1 - on
+    | |
+     -------------------------------------- removable      0 - disable
+                                            as BIOS dev    1 - boot device
+                                                           2 - all
+
+Host flags 1 (addr 0x100001, 33)::
+
+    x x x x  x x x x  x x x x  x x x x
+               | | |             | | |
+               | | |              --------- boot delay     0 -   3 sec
+               | | |                                       1 -   5
+               | | |                                       2 -  10
+               | | |                                       3 -  20
+               | | |                                       4 -  30
+               | | |                                       5 -  60
+               | | |                                       6 - 120
+               | | |
+                --------------------------- max tag cmds   0 -  2
+                                                           1 -  4
+                                                           2 -  8
+                                                           3 - 16
+                                                           4 - 32
+
+Host flags 2 (addr 0x100010, 34)::
+
+    x x x x  x x x x  x x x x  x x x x
+                                     |
+                                      ----- F2/F6 enable   0 - off ???
+                                                           1 - on  ???
+
+checksum (addr 0x111111)
+
+checksum = 0x1234 - (sum addr 0-63)
+
+----------------------------------------------------------------------------
+
+default nvram data::
+
+    0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000
+    0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000
+    0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000
+    0x0037 0x0000 0x0037 0x0000 0x0037 0x0000 0x0037 0x0000
+
+    0x0f07 0x0400 0x0001 0x0000 0x0000 0x0000 0x0000 0x0000
+    0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+    0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
+    0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0xfbbc