The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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sys/dev/ic/README.ncr5380sbc

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    1 NCR 53C80/53C400 driver
    2 
    3 BACKGROUND
    4 ----------
    5 The NCR 53C80 SCSI Bus Controller (SBC) is an early single-chip solution
    6 which formed the basis of many early SCSI host adapters for both the
    7 i386 and m68k platforms. The NCR 53C400 is a slightly more advanced
    8 chip which retains backward compatibility with the 53C80.
    9 
   10 On the PC, the NCR 53C80 was most commonly used to implement simple, cheap
   11 SCSI host adapters that were bundled with tape and CD-ROM drives. Since
   12 these controllers were not bus-mastering (and in some cases were not even
   13 interrupt-driven), they (like IDE adapters) required the CPU to perform
   14 much of the actual processing. These days, these controllers are cheap
   15 and plentiful since many are not supported by Windows 95.
   16 
   17 Similarly, NetBSD, although it has had an MI 53C80 driver (used by the
   18 Sun3 and Mac68k ports) for some time, has not had a i386 driver.
   19 
   20 Until now, that is...
   21 
   22 OVERVIEW
   23 --------
   24 The NCR 53C80/53C400 driver (the 'nca' device) consists of two pieces:
   25 
   26         1) Patches for the 53C80 MI driver to make it use bus_space()
   27            functions. (This requires an optional define. By default,
   28            the driver will compile in "legacy" memory-mapped mode.
   29 
   30         2) A machine-dependent driver (nca) containing probe and
   31            attachment routines.
   32 
   33 This driver has bene tested with the following adapters:
   34 
   35         NCS-250 (Chinon)        53C80, port-mapped, polled-mode
   36                                 (This is used in my primary development
   37                                 box to drive an external Zip drive.)
   38         Sumo SCSI-AT            53C80, port-mapped, interrupt driven
   39                                 (Note: This is an odd card in that its
   40                                 own firmware seems to have trouble detecting
   41                                 attached drives. Under NetBSD, however,
   42                                 it operates with no problems.)
   43         Trantor T-160           53C400, port-mapped, interrupt driven
   44                                 This card was often bundled with NEC
   45                                 CD-ROM drives. (My standalone test box
   46                                 is using this as its primary adapter.)
   47         DTC 3150V               53C400, memory-mapped, interrupt driven
   48                                 This a simple card designed to drive
   49                                 a CD-ROM.
   50 
   51 CONFIGURATION
   52 -------------
   53 To setup the nca driver, the configuration file must contain the following:
   54 
   55         options NCR5380_USE_BUS_SPACE
   56 
   57 This line is required to add bus_space() compatibility to the MI driver.
   58 
   59 Next you need to add one or more configuration lines for the nca devices:
   60 
   61         nca0    at isa? port 0x360 irq 15
   62         nca1    at isa? iomem 0xd8000 irq 5
   63 
   64 The first is for a port-mapped controller at 0x360, IRQ 15. The second line
   65 is for a memory-mapped controller (Trantor T128 or equivalent) at
   66 0xd800-0xdff, IRQ 5.
   67 
   68 You can also set up the driver in "polled" mode (i.e., no interrupts) by
   69 leaving off the "irq" portion of the line:
   70 
   71         nca0    at isa? port 0x360
   72         nca1    at isa? iomem 0xd8000
   73 
   74 Lastly, you need to add a scsibus attachment line for the nca device:
   75 
   76         scsibus* at nca?
   77 
   78 The following is the probe output from my test system:
   79 
   80         Copyright (c) 1996, 1997, 1998
   81             The NetBSD Foundation, Inc.  All rights reserved.
   82         Copyright (c) 1982, 1986, 1989, 1991, 1993
   83             The Regents of the University of California.  All rights reserved.
   84 
   85         NetBSD 1.3.2 (GENERIC) #2: Sun Oct  4 17:11:43 EDT 1998
   86             root@hefalump:/usr/src/sys/arch/i386/compile/GENERIC
   87         cpu0: Intel 486DX (486-class)
   88         real mem  = 7995392
   89         avail mem = 5349376
   90         using 123 buffers containing 503808 bytes of memory
   91         mainbus0 (root)
   92         isa0 at mainbus0
   93         com1 at isa0 port 0x2f8-0x2ff irq 3: ns8250 or ns16450, no fifo
   94         com2 at isa0 port 0x3e8-0x3ef irq 5: ns8250 or ns16450, no fifo
   95         lpt0 at isa0 port 0x378-0x37b irq 7
   96         nca0 at isa0 port 0x360-0x36f irq 15
   97         nca0: NCR 53C400 detected
   98         scsibus0 at nca0: 8 targets
   99         sd0 at scsibus0 targ 0 lun 0: <HP, C2235, 0B11> SCSI2 0/direct fixed
  100         sd0: 402MB, 1574 cyl, 9 head, 58 sec, 512 bytes/sect x 825012 sectors
  101         cd0 at scsibus0 targ 6 lun 0: <CHINON, CD-ROM CDS-535, Q20> SCSI2 5/cdrom removable
  102         nca1 at isa0 iomem 0xdb878-0xdb887 irq 5
  103         nca1: NCR 53C400 detected
  104         scsibus1 at nca1: 8 targets
  105         sd1 at scsibus1 targ 5 lun 0: <IOMEGA, ZIP 100, J.02> SCSI2 0/direct removable
  106         sd1: 96MB, 96 cyl, 64 head, 32 sec, 512 bytes/sect x 196608 sectors
  107         npx0 at isa0 port 0xf0-0xff: using exception 16
  108         pc0 at isa0 port 0x60-0x6f irq 1: color
  109         pc0: console
  110         fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
  111         fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec
  112         biomask 8060 netmask 8460 ttymask 84e2
  113         boot device: sd0
  114         root on sd0a dumps on sd0b
  115         root file system type: ffs
  116 
  117 In this output, nca0 is a Trantor T-160 and nca1 is a DTC 3150V. Both happen
  118 to be 53C400-based controllers.
  119 
  120 LIMITATIONS
  121 -----------
  122 As of this writing, the nca driver has two known limitations:
  123 
  124 1) No DMA or pseudo-DMA support
  125 
  126 This is unfortunate, but may be remedied in a later release. I would welcome
  127 any help by someone more familiar with DMA, particularly in relation to
  128 bus_space().
  129 
  130 As it is, however, performance of the nca driver is acceptable, though some
  131 of that may depend on one's definition of "acceptable". Remember that these
  132 were not high speed controller under the best conditions, so much of it is
  133 really the nature of the beast. It should be adequate for tapes, CD-ROMS,
  134 and low-usage disk devices (e.g., Zip drives). If you want to drive a CD-R
  135 drive, then invest in an Adaptec 154X or a PCI controller.
  136 
  137 2) No support for the SCSI port of the Pro AudioStudio 16.
  138 
  139 This is also unfortunate and may not be able to be remedied withing the
  140 current framework of the bus_space() functions and the nca driver.
  141 
  142 The problem is this: In most adapters, the eight 53C80 registers are mapped
  143 to eight sequential locations, either ports or memory addresses. On the
  144 PAS-16, however, the registers are mapped to two sets of ports- four
  145 sequential ports at the base address and four sequential ports located
  146 0x2000 higher. As I currently understand it, this is not supportable by
  147 the current bus_space() implementation nor is it possible for the driver
  148 to allocate a second bus_space_tag and _handle itself to accommodate the
  149 second set of ports. Without either, it is very difficult to imagine how
  150 a portable linkage to the MI driver could be made.
  151 
  152 Again, I welcome suggestions.
  153 
  154 HISTORY
  155 -------
  156 An nca driver first appeared in FreeBSD.
  157 
  158 This particular one borrows a little code from it and some from the i386
  159 'esp' and sun3 'si' drivers. It, like many things in the free unix world,
  160 was written because it solved a problem- mine! In my case, it was a need
  161 of a SCSI card and a lack of IRQs. The good news was that I had one
  162 (NCS-250); the bad news was that it was not supported under NetBSD. The
  163 rest is history.
  164 
  165 DISCLAIMER
  166 ----------
  167 Like most things, you should take this code with a grain of salt. I have
  168 tried to test it sufficiently, but it is always possible that it is not
  169 compatible with some aspect of your system. If you end up suffering
  170 massive data loss and destruction, you have my sympathies, but I do not
  171 and will not allow myself to be held responsible.
  172 
  173 CREDITS
  174 -------
  175 My thanks to Jason Thorpe and the rest of the NetBSD team for making it
  176 so easy to write this driver. My thanks also to the authors of the
  177 FreeBSD nca driver for inspiration and 53C400 support.
  178 
  179 In the end, I hope that someone else can find this driver as useful as I
  180 have. If so, please drop me a line at jruschme@exit109.com and let me
  181 know about it.
  182 
  183 Share and enjoy
  184 
  185 John Ruschmeyer (jruschme@exit109.com)
  186 11 October 1998

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