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-i386 Micro Channel Architecture Support
-=======================================
-
-MCA support is enabled using the CONFIG_MCA define. A machine with a MCA
-bus will have the kernel variable MCA_bus set, assuming the BIOS feature
-bits are set properly (see arch/i386/boot/setup.S for information on
-how this detection is done).
-
-Adapter Detection
-=================
-
-The ideal MCA adapter detection is done through the use of the
-Programmable Option Select registers. Generic functions for doing
-this have been added in include/linux/mca.h and arch/x86/kernel/mca_32.c.
-Everything needed to detect adapters and read (and write) configuration
-information is there. A number of MCA-specific drivers already use
-this. The typical probe code looks like the following:
-
- #include <linux/mca.h>
-
- unsigned char pos2, pos3, pos4, pos5;
- struct net_device* dev;
- int slot;
-
- if( MCA_bus ) {
- slot = mca_find_adapter( ADAPTER_ID, 0 );
- if( slot == MCA_NOTFOUND ) {
- return -ENODEV;
- }
- /* optional - see below */
- mca_set_adapter_name( slot, "adapter name & description" );
- mca_set_adapter_procfn( slot, dev_getinfo, dev );
-
- /* read the POS registers. Most devices only use 2 and 3 */
- pos2 = mca_read_stored_pos( slot, 2 );
- pos3 = mca_read_stored_pos( slot, 3 );
- pos4 = mca_read_stored_pos( slot, 4 );
- pos5 = mca_read_stored_pos( slot, 5 );
- } else {
- return -ENODEV;
- }
-
- /* extract configuration from pos[2345] and set everything up */
-
-Loadable modules should modify this to test that the specified IRQ and
-IO ports (plus whatever other stuff) match. See 3c523.c for example
-code (actually, smc-mca.c has a slightly more complex example that can
-handle a list of adapter ids).
-
-Keep in mind that devices should never directly access the POS registers
-(via inb(), outb(), etc). While it's generally safe, there is a small
-potential for blowing up hardware when it's done at the wrong time.
-Furthermore, accessing a POS register disables a device temporarily.
-This is usually okay during startup, but do _you_ want to rely on it?
-During initial configuration, mca_init() reads all the POS registers
-into memory. mca_read_stored_pos() accesses that data. mca_read_pos()
-and mca_write_pos() are also available for (safer) direct POS access,
-but their use is _highly_ discouraged. mca_write_pos() is particularly
-dangerous, as it is possible for adapters to be put in inconsistent
-states (i.e. sharing IO address, etc) and may result in crashes, toasted
-hardware, and blindness.
-
-User level drivers (such as the AGX X server) can use /proc/mca/pos to
-find adapters (see below).
-
-Some MCA adapters can also be detected via the usual ISA-style device
-probing (many SCSI adapters, for example). This sort of thing is highly
-discouraged. Perfectly good information is available telling you what's
-there, so there's no excuse for messing with random IO ports. However,
-we MCA people still appreciate any ISA-style driver that will work with
-our hardware. You take what you can get...
-
-Level-Triggered Interrupts
-==========================
-
-Because MCA uses level-triggered interrupts, a few problems arise with
-what might best be described as the ISA mindset and its effects on
-drivers. These sorts of problems are expected to become less common as
-more people use shared IRQs on PCI machines.
-
-In general, an interrupt must be acknowledged not only at the ICU (which
-is done automagically by the kernel), but at the device level. In
-particular, IRQ 0 must be reset after a timer interrupt (now done in
-arch/x86/kernel/time.c) or the first timer interrupt hangs the system.
-There were also problems with the 1.3.x floppy drivers, but that seems
-to have been fixed.
-
-IRQs are also shareable, and most MCA-specific devices should be coded
-with shared IRQs in mind.
-
-/proc/mca
-=========
-
-/proc/mca is a directory containing various files for adapters and
-other stuff.
-
- /proc/mca/pos Straight listing of POS registers
- /proc/mca/slot[1-8] Information on adapter in specific slot
- /proc/mca/video Same for integrated video
- /proc/mca/scsi Same for integrated SCSI
- /proc/mca/machine Machine information
-
-See Appendix A for a sample.
-
-Device drivers can easily add their own information function for
-specific slots (including integrated ones) via the
-mca_set_adapter_procfn() call. Drivers that support this are ESDI, IBM
-SCSI, and 3c523. If a device is also a module, make sure that the proc
-function is removed in the module cleanup. This will require storing
-the slot information in a private structure somewhere. See the 3c523
-driver for details.
-
-Your typical proc function will look something like this:
-
- static int
- dev_getinfo( char* buf, int slot, void* d ) {
- struct net_device* dev = (struct net_device*) d;
- int len = 0;
-
- len += sprintf( buf+len, "Device: %s\n", dev->name );
- len += sprintf( buf+len, "IRQ: %d\n", dev->irq );
- len += sprintf( buf+len, "IO Port: %#lx-%#lx\n", ... );
- ...
-
- return len;
- }
-
-Some of the standard MCA information will already be printed, so don't
-bother repeating it. Don't try putting in more than 3K of information.
-
-Enable this function with:
- mca_set_adapter_procfn( slot, dev_getinfo, dev );
-
-Disable it with:
- mca_set_adapter_procfn( slot, NULL, NULL );
-
-It is also recommended that, even if you don't write a proc function, to
-set the name of the adapter (i.e. "PS/2 ESDI Controller") via
-mca_set_adapter_name( int slot, char* name ).
-
-MCA Device Drivers
-==================
-
-Currently, there are a number of MCA-specific device drivers.
-
-1) PS/2 SCSI
- drivers/scsi/ibmmca.c
- drivers/scsi/ibmmca.h
- The driver for the IBM SCSI subsystem. Includes both integrated
- controllers and adapter cards. May require command-line arg
- "ibmmcascsi=io_port" to force detection of an adapter. If you have a
- machine with a front-panel display (i.e. model 95), you can use
- "ibmmcascsi=display" to enable a drive activity indicator.
-
-2) 3c523
- drivers/net/3c523.c
- drivers/net/3c523.h
- 3Com 3c523 Etherlink/MC ethernet driver.
-
-3) SMC Ultra/MCA and IBM Adapter/A
- drivers/net/smc-mca.c
- drivers/net/smc-mca.h
- Driver for the MCA version of the SMC Ultra and various other
- OEM'ed and work-alike cards (Elite, Adapter/A, etc).
-
-4) NE/2
- driver/net/ne2.c
- driver/net/ne2.h
- The NE/2 is the MCA version of the NE2000. This may not work
- with clones that have a different adapter id than the original
- NE/2.
-
-5) Future Domain MCS-600/700, OEM'd IBM Fast SCSI Adapter/A and
- Reply Sound Blaster/SCSI (SCSI part)
- Better support for these cards than the driver for ISA.
- Supports multiple cards with IRQ sharing.
-
-Also added boot time option of scsi-probe, which can do reordering of
-SCSI host adapters. This will direct the kernel on the order which
-SCSI adapter should be detected. Example:
- scsi-probe=ibmmca,fd_mcs,adaptec1542,buslogic
-
-The serial drivers were modified to support the extended IO port range
-of the typical MCA system (also #ifdef CONFIG_MCA).
-
-The following devices work with existing drivers:
-1) Token-ring
-2) Future Domain SCSI (MCS-600, MCS-700, not MCS-350, OEM'ed IBM SCSI)
-3) Adaptec 1640 SCSI (using the aha1542 driver)
-4) Bustek/Buslogic SCSI (various)
-5) Probably all Arcnet cards.
-6) Some, possibly all, MCA IDE controllers.
-7) 3Com 3c529 (MCA version of 3c509) (patched)
-
-8) Intel EtherExpressMC (patched version)
- You need to have CONFIG_MCA defined to have EtherExpressMC support.
-9) Reply Sound Blaster/SCSI (SB part) (patched version)
-
-Bugs & Other Weirdness
-======================
-
-NMIs tend to occur with MCA machines because of various hardware
-weirdness, bus timeouts, and many other non-critical things. Some basic
-code to handle them (inspired by the NetBSD MCA code) has been added to
-detect the guilty device, but it's pretty incomplete. If NMIs are a
-persistent problem (on some model 70 or 80s, they occur every couple
-shell commands), the CONFIG_IGNORE_NMI flag will take care of that.
-
-Various Pentium machines have had serious problems with the FPU test in
-bugs.h. Basically, the machine hangs after the HLT test. This occurs,
-as far as we know, on the Pentium-equipped 85s, 95s, and some PC Servers.
-The PCI/MCA PC 750s are fine as far as I can tell. The ``mca-pentium''
-boot-prompt flag will disable the FPU bug check if this is a problem
-with your machine.
-
-The model 80 has a raft of problems that are just too weird and unique
-to get into here. Some people have no trouble while others have nothing
-but problems. I'd suspect some problems are related to the age of the
-average 80 and accompanying hardware deterioration, although others
-are definitely design problems with the hardware. Among the problems
-include SCSI controller problems, ESDI controller problems, and serious
-screw-ups in the floppy controller. Oh, and the parallel port is also
-pretty flaky. There were about 5 or 6 different model 80 motherboards
-produced to fix various obscure problems. As far as I know, it's pretty
-much impossible to tell which bugs a particular model 80 has (other than
-triggering them, that is).
-
-Drivers are required for some MCA memory adapters. If you're suddenly
-short a few megs of RAM, this might be the reason. The (I think) Enhanced
-Memory Adapter commonly found on the model 70 is one. There's a very
-alpha driver floating around, but it's pretty ugly (disassembled from
-the DOS driver, actually). See the MCA Linux web page (URL below)
-for more current memory info.
-
-The Thinkpad 700 and 720 will work, but various components are either
-non-functional, flaky, or we don't know anything about them. The
-graphics controller is supposed to be some WD, but we can't get things
-working properly. The PCMCIA slots don't seem to work. Ditto for APM.
-The serial ports work, but detection seems to be flaky.
-
-Credits
-=======
-A whole pile of people have contributed to the MCA code. I'd include
-their names here, but I don't have a list handy. Check the MCA Linux
-home page (URL below) for a perpetually out-of-date list.
-
-=====================================================================
-MCA Linux Home Page: http://www.dgmicro.com/mca/
-
-Christophe Beauregard
-chrisb@truespectra.com
-cpbeaure@calum.csclub.uwaterloo.ca
-
-=====================================================================
-Appendix A: Sample /proc/mca
-
-This is from my model 8595. Slot 1 contains the standard IBM SCSI
-adapter, slot 3 is an Adaptec AHA-1640, slot 5 is a XGA-1 video adapter,
-and slot 7 is the 3c523 Etherlink/MC.
-
-/proc/mca/machine:
-Model Id: 0xf8
-Submodel Id: 0x14
-BIOS Revision: 0x5
-
-/proc/mca/pos:
-Slot 1: ff 8e f1 fc a0 ff ff ff IBM SCSI Adapter w/Cache
-Slot 2: ff ff ff ff ff ff ff ff
-Slot 3: 1f 0f 81 3b bf b6 ff ff
-Slot 4: ff ff ff ff ff ff ff ff
-Slot 5: db 8f 1d 5e fd c0 00 00
-Slot 6: ff ff ff ff ff ff ff ff
-Slot 7: 42 60 ff 08 ff ff ff ff 3Com 3c523 Etherlink/MC
-Slot 8: ff ff ff ff ff ff ff ff
-Video : ff ff ff ff ff ff ff ff
-SCSI : ff ff ff ff ff ff ff ff
-
-/proc/mca/slot1:
-Slot: 1
-Adapter Name: IBM SCSI Adapter w/Cache
-Id: 8eff
-Enabled: Yes
-POS: ff 8e f1 fc a0 ff ff ff
-Subsystem PUN: 7
-Detected at boot: Yes
-
-/proc/mca/slot3:
-Slot: 3
-Adapter Name: Unknown
-Id: 0f1f
-Enabled: Yes
-POS: 1f 0f 81 3b bf b6 ff ff
-
-/proc/mca/slot5:
-Slot: 5
-Adapter Name: Unknown
-Id: 8fdb
-Enabled: Yes
-POS: db 8f 1d 5e fd c0 00 00
-
-/proc/mca/slot7:
-Slot: 7
-Adapter Name: 3Com 3c523 Etherlink/MC
-Id: 6042
-Enabled: Yes
-POS: 42 60 ff 08 ff ff ff ff
-Revision: 0xe
-IRQ: 9
-IO Address: 0x3300-0x3308
-Memory: 0xd8000-0xdbfff
-Transceiver: External
-Device: eth0
-Hardware Address: 02 60 8c 45 c4 2a