187 lines
7.1 KiB
Plaintext
187 lines
7.1 KiB
Plaintext
NCR 53C80/53C400 driver
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BACKGROUND
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----------
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The NCR 53C80 SCSI Bus Controller (SBC) is an early single-chip solution
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which formed the basis of many early SCSI host adapters for both the
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i386 and m68k platforms. The NCR 53C400 is a slightly more advanced
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chip which retains backward compatibility with the 53C80.
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On the PC, the NCR 53C80 was most commonly used to implement simple, cheap
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SCSI host adapters that were bundled with tape and CD-ROM drives. Since
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these controllers were not bus-mastering (and in some cases were not even
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interrupt-driven), they (like IDE adapters) required the CPU to perform
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much of the actual processing. These days, these controllers are cheap
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and plentiful since many are not supported by Windows 95.
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Similarly, NetBSD, although it has had an MI 53C80 driver (used by the
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Sun3 and Mac68k ports) for some time, has not had a i386 driver.
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Until now, that is...
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OVERVIEW
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--------
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The NCR 53C80/53C400 driver (the 'nca' device) consists of two pieces:
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1) Patches for the 53C80 MI driver to make it use bus_space()
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functions. (This requires an optional define. By default,
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the driver will compile in "legacy" memory-mapped mode.
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2) A machine-dependent driver (nca) containing probe and
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attachment routines.
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This driver has bene tested with the following adapters:
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NCS-250 (Chinon) 53C80, port-mapped, polled-mode
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(This is used in my primary development
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box to drive an external Zip drive.)
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Sumo SCSI-AT 53C80, port-mapped, interrupt driven
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(Note: This is an odd card in that its
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own firmware seems to have trouble detecting
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attached drives. Under NetBSD, however,
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it operates with no problems.)
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Trantor T-160 53C400, port-mapped, interrupt driven
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This card was often bundled with NEC
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CD-ROM drives. (My standalone test box
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is using this as its primary adapter.)
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DTC 3150V 53C400, memory-mapped, interrupt driven
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This a simple card designed to drive
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a CD-ROM.
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CONFIGURATION
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-------------
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To setup the nca driver, the configuration file must contain the following:
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options NCR5380_USE_BUS_SPACE
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This line is required to add bus_space() compatibility to the MI driver.
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Next you need to add one or more configuration lines for the nca devices:
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nca0 at isa? port 0x360 irq 15
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nca1 at isa? iomem 0xd8000 irq 5
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The first is for a port-mapped controller at 0x360, IRQ 15. The second line
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is for a memory-mapped controller (Trantor T128 or equivalent) at
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0xd800-0xdff, IRQ 5.
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You can also set up the driver in "polled" mode (i.e., no interrupts) by
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leaving off the "irq" portion of the line:
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nca0 at isa? port 0x360
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nca1 at isa? iomem 0xd8000
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Lastly, you need to add a scsibus attachment line for the nca device:
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scsibus* at nca?
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The following is the probe output from my test system:
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Copyright (c) 1996, 1997, 1998
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The NetBSD Foundation, Inc. All rights reserved.
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Copyright (c) 1982, 1986, 1989, 1991, 1993
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The Regents of the University of California. All rights reserved.
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NetBSD 1.3.2 (GENERIC) #2: Sun Oct 4 17:11:43 EDT 1998
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root@hefalump:/usr/src/sys/arch/i386/compile/GENERIC
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cpu0: Intel 486DX (486-class)
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real mem = 7995392
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avail mem = 5349376
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using 123 buffers containing 503808 bytes of memory
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mainbus0 (root)
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isa0 at mainbus0
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com1 at isa0 port 0x2f8-0x2ff irq 3: ns8250 or ns16450, no fifo
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com2 at isa0 port 0x3e8-0x3ef irq 5: ns8250 or ns16450, no fifo
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lpt0 at isa0 port 0x378-0x37b irq 7
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nca0 at isa0 port 0x360-0x36f irq 15
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nca0: NCR 53C400 detected
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scsibus0 at nca0: 8 targets
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sd0 at scsibus0 targ 0 lun 0: <HP, C2235, 0B11> SCSI2 0/direct fixed
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sd0: 402MB, 1574 cyl, 9 head, 58 sec, 512 bytes/sect x 825012 sectors
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cd0 at scsibus0 targ 6 lun 0: <CHINON, CD-ROM CDS-535, Q20> SCSI2 5/cdrom removable
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nca1 at isa0 iomem 0xdb878-0xdb887 irq 5
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nca1: NCR 53C400 detected
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scsibus1 at nca1: 8 targets
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sd1 at scsibus1 targ 5 lun 0: <IOMEGA, ZIP 100, J.02> SCSI2 0/direct removable
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sd1: 96MB, 96 cyl, 64 head, 32 sec, 512 bytes/sect x 196608 sectors
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npx0 at isa0 port 0xf0-0xff: using exception 16
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pc0 at isa0 port 0x60-0x6f irq 1: color
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pc0: console
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fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
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fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec
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biomask 8060 netmask 8460 ttymask 84e2
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boot device: sd0
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root on sd0a dumps on sd0b
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root file system type: ffs
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In this output, nca0 is a Trantor T-160 and nca1 is a DTC 3150V. Both happen
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to be 53C400-based controllers.
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LIMITATIONS
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-----------
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As of this writing, the nca driver has two known limitations:
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1) No DMA or pseudo-DMA support
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This is unfortunate, but may be remedied in a later release. I would welcome
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any help by someone more familiar with DMA, particularly in relation to
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bus_space().
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As it is, however, performance of the nca driver is acceptable, though some
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of that may depend on one's definition of "acceptable". Remember that these
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were not high speed controller under the best conditions, so much of it is
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really the nature of the beast. It should be adequate for tapes, CD-ROMS,
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and low-usage disk devices (e.g., Zip drives). If you want to drive a CD-R
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drive, then invest in an Adaptec 154X or a PCI controller.
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2) No support for the SCSI port of the Pro AudioStudio 16.
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This is also unfortunate and may not be able to be remedied withing the
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current framework of the bus_space() functions and the nca driver.
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The problem is this: In most adapters, the eight 53C80 registers are mapped
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to eight sequential locations, either ports or memory addresses. On the
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PAS-16, however, the registers are mapped to two sets of ports- four
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sequential ports at the base address and four sequential ports located
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0x2000 higher. As I currently understand it, this is not supportable by
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the current bus_space() implementation nor is it possible for the driver
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to allocate a second bus_space_tag and _handle itself to accomodate the
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second set of ports. Without either, it is very difficult to imagine how
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a portable linkage to the MI driver could be made.
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Again, I welcome suggestions.
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HISTORY
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An nca driver first appeared in FreeBSD.
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This particular one borrows a little code from it and some from the i386
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'esp' and sun3 'si' drivers. It, like many things in the free unix world,
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was written because it solved a problem- mine! In my case, it was a need
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of a SCSI card and a lack of IRQs. The good news was that I had one
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(NCS-250); the bad news was that it was not supported under NetBSD. The
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rest is history.
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DISCLAIMER
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Like most things, you should take this code with a grain of salt. I have
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tried to test it sufficiently, but it is always possible that it is not
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compatible with some aspect of your system. If you end up suffering
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massive data loss and destruction, you have my sympathies, but I do not
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and will not allow myself to be held responsible.
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CREDITS
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-------
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My thanks to Jason Thorpe and the rest of the NetBSD team for making it
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so easy to write this driver. My thanks also to the authors of the
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FreeBSD nca driver for inspiration and 53C400 support.
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In the end, I hope that someone else can find this driver as useful as I
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have. If so, please drop me a line at jruschme@exit109.com and let me
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know about it.
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Share and enjoy
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John Ruschmeyer (jruschme@exit109.com)
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11 October 1998
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