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diff --git a/Documentation/mca.txt b/Documentation/mca.txt new file mode 100644 index 0000000..6e32c30 --- /dev/null +++ b/Documentation/mca.txt @@ -0,0 +1,320 @@ +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/i386/kernel/mca.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/i386/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 ESDI + drivers/block/ps2esdi.c + include/linux/ps2esdi.h + Uses major number 36, and should use /dev files /dev/eda, /dev/edb. + Supports two drives, but only one controller. May use the + command-line args "ed=cyl,head,sec" and "tp720". + +2) 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. + +3) 3c523 + drivers/net/3c523.c + drivers/net/3c523.h + 3Com 3c523 Etherlink/MC ethernet driver. + +4) 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). + +5) 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. + +6) Future Domain MCS-600/700, OEM'd IBM Fast SCSI Aapter/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://glycerine.itsmm.uni.edu/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 |
